All books on paleontology that go into detail about Ichthyosaurs agree that they gave live birth: the fossil evidence for that is overwhelming.
The only ones I've found that discuss what happens before the live birth
are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_, which agree that they were ovoviviparous. Colbert writes:
So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
In contrast, Carroll only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.
Wikipedia's entry simply claims they are viviparous and references an 1846 [NOT 1946] article by J.C. Pearce for it.
In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity. https://en.wikipedia.org/wiki/Viviparity
Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.
Does anyone here have any ideas for other (probably much weaker)
evidence for one form or the other?
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos
All books on paleontology that go into detail about Ichthyosaurs agree that they gave live birth: the fossil evidence for that is overwhelming.
The only ones I've found that discuss what happens before the live birth
are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_, which agree that they were ovoviviparous. Colbert writes:
So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
In contrast, Carroll only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.
Wikipedia's entry simply claims they are viviparous and references an 1846 [NOT 1946] article by J.C. Pearce for it.
In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity. https://en.wikipedia.org/wiki/Viviparity
Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.
Does anyone here have any ideas for other (probably much weaker)
evidence for one form or the other?
On Friday, August 26, 2022 at 6:39:46 AM UTC-7, peter2...@gmail.com wrote:
All books on paleontology that go into detail about Ichthyosaurs agree that
they gave live birth: the fossil evidence for that is overwhelming.
The only ones I've found that discuss what happens before the live birth are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_, which agree that they were ovoviviparous. Colbert writes:
So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
In contrast, Carroll [1988] only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.
Wikipedia's entry simply claims they are viviparous and references an 1846 [NOT 1946] article by J.C. Pearce for it.
In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity. https://en.wikipedia.org/wiki/Viviparity
Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.
Does anyone here have any ideas for other (probably much weaker)
evidence for one form or the other?
Peter NyikosEvidence for viviparity in ichthyosaurs having appeared in land-living ancestors:
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088640 https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0088640&type=printable (open access)
On Friday, August 26, 2022 at 11:37:49 AM UTC-4, erik simpson wrote:
On Friday, August 26, 2022 at 6:39:46 AM UTC-7, peter2...@gmail.com wrote:
All books on paleontology that go into detail about Ichthyosaurs agree that
they gave live birth: the fossil evidence for that is overwhelming.
The only ones I've found that discuss what happens before the live birth are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_,
which agree that they were ovoviviparous. Colbert writes:
So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
In contrast, Carroll [1988] only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.
Wikipedia's entry simply claims they are viviparous and references an 1846
[NOT 1946] article by J.C. Pearce for it.
In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes
four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity. https://en.wikipedia.org/wiki/Viviparity
Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some
Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.
Does anyone here have any ideas for other (probably much weaker) evidence for one form or the other?
including cases of egg retention up to limb-bud stage, and viviparity involving functional placentation [2], with few intermediate forms [22]. Therefore, viviparity seems to evolve simultaneously with functional placentation in squamates [23]. GivenPeter NyikosEvidence for viviparity in ichthyosaurs having appeared in land-living ancestors:
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088640 https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0088640&type=printable (open access)Two copies of the same article, as far as I could tell.
Unfortunately, the authors' argument for viviparity is very weak.
The following seems to be as close as they try to come:
Viviparity in extant reptiles is known only among squamates. Despite the traditional four-step evolutionary model from lecithotrophy to placentotrophy, squamate reproductive strategies are almost bimodally divided between oviparity (egg laying),
[22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
to the article itself! The same goes for [23].
My time today for posting is limited, so for the moment I have to fall back on Wikipedia,
specifically the link I gave earlier, https://en.wikipedia.org/wiki/Viviparity and the following:
https://en.wikipedia.org/wiki/Ovoviviparity
Unfortunately, this gives no reptilian examples, while the other website only has this:
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae)."
There is a link for "vipers," but its talk of their reproduction only takes us back to
https://en.wikipedia.org/wiki/Viviparity
Looks like we need to borrow a term from chess for this kind of frustration:
"Draw by perpetual check" :)
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
Univ. of South Carolina at Columbia
http://people.math.sc.edu/nyikos
On Friday, August 26, 2022 at 9:49:20 AM UTC-7, peter2...@gmail.com wrote:
On Friday, August 26, 2022 at 11:37:49 AM UTC-4, erik simpson wrote:
On Friday, August 26, 2022 at 6:39:46 AM UTC-7, peter2...@gmail.com wrote:
All books on paleontology that go into detail about Ichthyosaurs agree that
they gave live birth: the fossil evidence for that is overwhelming.
The only ones I've found that discuss what happens before the live birth
are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_,
which agree that they were ovoviviparous. Colbert writes:
So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
In contrast, Carroll [1988] only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.
Wikipedia's entry simply claims they are viviparous and references an 1846
[NOT 1946] article by J.C. Pearce for it.
In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes
four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity. https://en.wikipedia.org/wiki/Viviparity
Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some
Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.
Does anyone here have any ideas for other (probably much weaker) evidence for one form or the other?
Peter NyikosEvidence for viviparity in ichthyosaurs having appeared in land-living ancestors:
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088640Two copies of the same article, as far as I could tell.
https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0088640&type=printable (open access)
Unfortunately, the authors' argument for viviparity is very weak.
The following seems to be as close as they try to come:
including cases of egg retention up to limb-bud stage, and viviparity involving functional placentation [2], with few intermediate forms [22]. Therefore, viviparity seems to evolve simultaneously with functional placentation in squamates [23]. GivenViviparity in extant reptiles is known only among squamates. Despite the traditional four-step evolutionary model from lecithotrophy to placentotrophy, squamate reproductive strategies are almost bimodally divided between oviparity (egg laying),
[22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
to the article itself! The same goes for [23].
My time today for posting is limited, so for the moment I have to fall back on Wikipedia,
specifically the link I gave earlier, https://en.wikipedia.org/wiki/Viviparity and the following:
https://en.wikipedia.org/wiki/Ovoviviparity
Unfortunately, this gives no reptilian examples, while the other website only has this:
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae)."
There is a link for "vipers," but its talk of their reproduction only takes us back to
https://en.wikipedia.org/wiki/Viviparity
Looks like we need to borrow a term from chess for this kind of frustration:
"Draw by perpetual check" :)
I knew I'd seen something about this and I found the paper in my collection of PDFs. Checking online, it's
still there as I cited. Both cite are the same, one (potentially?) paywalled.
From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)
The Wiki entry does suggest caution with the use of the term ovoviviparity as "poorly and inconsistently defined, and may be obsolete.
This term has been redefined and more commonly referred to as oviparous egg retention or prolonged egg retention."
So yeah, ichthyosaurs aren't squamates, and there's no evidence of egg retention,
but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
soft tissue is not preserved."
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
Univ. of South Carolina in Columbia
http://people.math.sc.edu/nyikos
On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote:
On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.
You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
and viviparity involving functional placentation". I don't understand what's frustrating.
but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
soft tissue is not preserved."
From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)
"almost bimodally, ... with few intermediate forms."
On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
Univ. of South Carolina in Columbia
http://people.math.sc.edu/nyikos
Wasn’t there something about reptile eggs needing to breathe or something? I supose amphibian eggs can be underwater; are reptile eggs the same way?
On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote: >>> On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.
You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
and viviparity involving functional placentation". I don't understand what's frustrating.
The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
viviparity in ichthyosaurs, which is at the exact resonant center of this thread.
I guess the shortness of the post attracted you like a magnet, causing you
to miss out on the original post, including the following reasoning:
___________________________ first excerpt from the original post_________________
but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
soft tissue is not preserved."
This is the second subset of what I quoted, and is why I find vipers so frustrating.
For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].
======================== end of first excerpt =======================
And here is why the "Given" is seriously affected:
######################## second excerpt from the original post #####################
From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)
This is the first subset that I mentioned above.
************************************************************ end of second excerpt
from https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?
And, lest your memory fail you between the first repost and the second, compare:
"make the inference almost untenable, given the variety of vipers".
and
"almost bimodally, ... with few intermediate forms."
Capice?
Sorry everyone, Mr. Slow here again (I’m the one for whom the saying, “He who laughs last did not get the joke” was invented)
Anyway, would it be correct to summarize the above as saying that reptiles evolved from true “egg laying” to simply keeping eggs within the body until they “hatched” several times within their history?
I guess that would make the difference between external egg laying and viviparous birth more of continuum than a hard line.
Would it be possible for something like Ichthyosaur eggs to evolve “backwards” from a hard reptilian shell egg back to goopy, unshelled, caviar-like blobs of jelly?
Wasn’t there something about reptile eggs needing to breathe or something? I supose amphibian eggs can be underwater; are reptile eggs the same way?
On 8/26/22 5:12 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote: >>> On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.
You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
and viviparity involving functional placentation". I don't understand what's frustrating.
The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
viviparity in ichthyosaurs, which is at the exact resonant center of this thread.
If you want to find about whether the claims in that paper are wrong,
you should consult the references cited to support the claims. In this
case that would seem to be references 2 and 22.
[end of repost][22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
to the article itself! The same goes for [23].
I guess the shortness of the post attracted you like a magnet, causing you to miss out on the original post, including the following reasoning:
___________________________ first excerpt from the original post_________________
but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
soft tissue is not preserved."
This is the second subset of what I quoted, and is why I find vipers so frustrating.
For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
======================== end of first excerpt =======================
And here is why the "Given" is seriously affected:
######################## second excerpt from the original post #####################
From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)
This is the first subset that I mentioned above.
************************************************************ end of second excerpt
from https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ
Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?
And, lest your memory fail you between the first repost and the second, compare:
"make the inference almost untenable, given the variety of vipers".
and
"almost bimodally, ... with few intermediate forms."
The second quote would seem to entail that the first quote is wrong.
Have you tried looking at the cited references? Have you searched for a review of squamate viviparity?
Here's one: https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
Abstract: Squamate reptiles (lizards and snakes) are an ideal model
system for testing hypotheses regarding the evolution of viviparity
(live birth) in amniote vertebrates. Viviparity has evolved over 100
times in squamates, resulting in major changes in reproductive
physiology. At a minimum, all viviparous squamates exhibit placentae
formed by the appositions of maternal and embryonic tissues, which are homologous in origin with the tissues that form the placenta in therian mammals. These placentae facilitate adhesion of the conceptus to the
uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and calcium. However, most viviparous squamates continue to rely on yolk for nearly all of their organic nutrition. In contrast, some species, which
rely on the placenta for at least a portion of organic nutrition,
exhibit complex placental specializations associated with the transport
of amino acids and fatty acids. Some viviparous squamates also exhibit reduced immunocompetence during pregnancy, which could be the result of immunosuppression to protect developing embryos. Recent molecular
studies using both candidate-gene and next-generation sequencing
approaches have suggested that at least some of the genes and gene
families underlying these phenomena play similar roles in the uterus and placenta of viviparous mammals and squamates. Therefore, studies of the evolution of viviparity in squamates should inform hypotheses of the evolution of viviparity in all amniotes, including mammals.
Here's another: https://pubmed.ncbi.nlm.nih.gov/21573966/
There are more, but you can google.
Capice?
This would be a better discussion if you didn't resort to condescension
so early into it.
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
On 8/26/22 5:12 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote: >>>>> On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote:
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.
You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
and viviparity involving functional placentation". I don't understand what's frustrating.
The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
viviparity in ichthyosaurs, which is at the exact resonant center of this thread.
If you want to find about whether the claims in that paper are wrong,
you should consult the references cited to support the claims. In this
case that would seem to be references 2 and 22.
[2] doesn't even use the term "ovoviviparous". It could, of course, be paraphrased
somewhere, but it's getting late and so I'm postponing this project for the weekend,
which means reporting on anything relevant on Monday or Tuesday.
As for [22], what I posted on that earlier was preserved in the post that neither Erik
nor you have shown any sign of having read, preferring the small correction which
followed it almost immediately.
[repost from uncorrected post]
[end of repost][22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
to the article itself! The same goes for [23].
I'll try to Google them on ResearchGate, like I did the reference you gave me next, but the
same thing applies that applies above.
I guess the shortness of the post attracted you like a magnet, causing you >>> to miss out on the original post, including the following reasoning:
___________________________ first excerpt from the original post_________________
but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
soft tissue is not preserved."
This is the second subset of what I quoted, and is why I find vipers so frustrating.
For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
======================== end of first excerpt =======================
And here is why the "Given" is seriously affected:
######################## second excerpt from the original post #####################
From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)
This is the first subset that I mentioned above.
************************************************************ end of second excerpt
from
https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ
Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?
And, lest your memory fail you between the first repost and the second, compare:
"make the inference almost untenable, given the variety of vipers".
and
"almost bimodally, ... with few intermediate forms."
The second quote would seem to entail that the first quote is wrong.
Have you tried looking at the cited references? Have you searched for a
review of squamate viviparity?
There has been too little time for that. The whole topic of this thread came as a brainstorm as I was lying awake this morning around 6 am.
Until then the issue had never occurred to me.
Here's one: https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml >>
Abstract: Squamate reptiles (lizards and snakes) are an ideal model
system for testing hypotheses regarding the evolution of viviparity
(live birth) in amniote vertebrates. Viviparity has evolved over 100
times in squamates, resulting in major changes in reproductive
physiology. At a minimum, all viviparous squamates exhibit placentae
formed by the appositions of maternal and embryonic tissues, which are
homologous in origin with the tissues that form the placenta in therian
mammals. These placentae facilitate adhesion of the conceptus to the
uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and
calcium. However, most viviparous squamates continue to rely on yolk for
nearly all of their organic nutrition. In contrast, some species, which
rely on the placenta for at least a portion of organic nutrition,
exhibit complex placental specializations associated with the transport
of amino acids and fatty acids. Some viviparous squamates also exhibit
reduced immunocompetence during pregnancy, which could be the result of
immunosuppression to protect developing embryos. Recent molecular
studies using both candidate-gene and next-generation sequencing
approaches have suggested that at least some of the genes and gene
families underlying these phenomena play similar roles in the uterus and
placenta of viviparous mammals and squamates. Therefore, studies of the
evolution of viviparity in squamates should inform hypotheses of the
evolution of viviparity in all amniotes, including mammals.
Thanks, that may be the first paper I look up.
Here's another: https://pubmed.ncbi.nlm.nih.gov/21573966/
There are more, but you can google.
Capice?
This would be a better discussion if you didn't resort to condescension
so early into it.
This from someone who has treated me with gratuitous condescension
in talk.origins for almost a dozen years, and in sci.bio.paleontology for about
half as long, with two completely contrasting breaks: Thrinaxodon (later nym: Oxyaena) almost
destroying s.b.p with relentless crazy spam, and what I call the Oasis
of Civilization Period, which lasted from mid-2015 to early 2018.
But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.
Peter Nyikos
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
On 8/26/22 5:12 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote:
On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote:
On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote: >>>>>
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.
You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
and viviparity involving functional placentation". I don't understand what's frustrating.
The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
viviparity in ichthyosaurs, which is at the exact resonant center of this thread.
If you want to find about whether the claims in that paper are wrong,
you should consult the references cited to support the claims. In this
case that would seem to be references 2 and 22.
[2] doesn't even use the term "ovoviviparous". It could, of course, be paraphrasedPerhaps 2 doesn't use it because it's not a useful term.
somewhere, but it's getting late and so I'm postponing this project for the weekend,
which means reporting on anything relevant on Monday or Tuesday.
As for [22], what I posted on that earlier was preserved in the post that neither Erik
nor you have shown any sign of having read, preferring the small correction which
followed it almost immediately.
[repost from uncorrected post]You may have to find the actual paper. Donk't your university resources
[end of repost][22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
to the article itself! The same goes for [23].
work for that?
I'll try to Google them on ResearchGate, like I did the reference you gave me next, but the
same thing applies that applies above.
I guess the shortness of the post attracted you like a magnet, causing you
to miss out on the original post, including the following reasoning:
___________________________ first excerpt from the original post_________________
but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
soft tissue is not preserved."
This is the second subset of what I quoted, and is why I find vipers so frustrating.
For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
======================== end of first excerpt =======================
And here is why the "Given" is seriously affected:
######################## second excerpt from the original post #####################
From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)
This is the first subset that I mentioned above.
************************************************************ end of second excerpt
from
https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ
Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?
And, lest your memory fail you between the first repost and the second, compare:
"make the inference almost untenable, given the variety of vipers".
and
"almost bimodally, ... with few intermediate forms."
The second quote would seem to entail that the first quote is wrong.
Have you tried looking at the cited references? Have you searched for a
review of squamate viviparity?
There has been too little time for that. The whole topic of this thread came
as a brainstorm as I was lying awake this morning around 6 am.
Until then the issue had never occurred to me.
Here's one: https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml >>
Abstract: Squamate reptiles (lizards and snakes) are an ideal model
system for testing hypotheses regarding the evolution of viviparity
(live birth) in amniote vertebrates. Viviparity has evolved over 100
times in squamates, resulting in major changes in reproductive
physiology. At a minimum, all viviparous squamates exhibit placentae
formed by the appositions of maternal and embryonic tissues, which are
homologous in origin with the tissues that form the placenta in therian
mammals. These placentae facilitate adhesion of the conceptus to the
uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and >> calcium. However, most viviparous squamates continue to rely on yolk for >> nearly all of their organic nutrition. In contrast, some species, which
rely on the placenta for at least a portion of organic nutrition,
exhibit complex placental specializations associated with the transport
of amino acids and fatty acids. Some viviparous squamates also exhibit
reduced immunocompetence during pregnancy, which could be the result of
immunosuppression to protect developing embryos. Recent molecular
studies using both candidate-gene and next-generation sequencing
approaches have suggested that at least some of the genes and gene
families underlying these phenomena play similar roles in the uterus and >> placenta of viviparous mammals and squamates. Therefore, studies of the
evolution of viviparity in squamates should inform hypotheses of the
evolution of viviparity in all amniotes, including mammals.
Thanks, that may be the first paper I look up.
Here's another: https://pubmed.ncbi.nlm.nih.gov/21573966/
There are more, but you can google.
Capice?
This would be a better discussion if you didn't resort to condescension
so early into it.
This from someone who has treated me with gratuitous condescensionYou have to start letting go of ancient grievances if you actually want
in talk.origins for almost a dozen years, and in sci.bio.paleontology for about
half as long, with two completely contrasting breaks: Thrinaxodon (later nym: Oxyaena) almost
destroying s.b.p with relentless crazy spam, and what I call the Oasis
of Civilization Period, which lasted from mid-2015 to early 2018.
to discuss the science.
But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.
Peter Nyikos
On Friday, August 26, 2022 at 8:54:00 PM UTC-7, John Harshman wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
On 8/26/22 5:12 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 7:16:18 PM UTC-4, erik simpson wrote: >>>> On Friday, August 26, 2022 at 3:42:40 PM UTC-7, peter2...@gmail.com wrote:
On Friday, August 26, 2022 at 6:32:49 PM UTC-4, Peter Nyikos wrote: >>>>>
You aren't contributing anything to the on-topic discussion in this second post of yours, Erik.
Minor technical exception: you completed the three-line description of Ovoviviparity in
https://en.wikipedia.org/wiki/Viviparity
of which I had posted the first sentence.
You're contributing what I see as a substantial digression into Mammalia. As for vipers, "squamate reproductive
strategies are almost bimodally divided between oviparity (egg laying), including cases of egg retention up to limb-bud stage,
and viviparity involving functional placentation". I don't understand what's frustrating.
The fact that the claim could be wrong [see reasoning below], and thus being used fallaciously to support
viviparity in ichthyosaurs, which is at the exact resonant center of this thread.
If you want to find about whether the claims in that paper are wrong,
you should consult the references cited to support the claims. In this >> case that would seem to be references 2 and 22.
[2] doesn't even use the term "ovoviviparous". It could, of course, be paraphrasedPerhaps 2 doesn't use it because it's not a useful term.
somewhere, but it's getting late and so I'm postponing this project for the weekend,
which means reporting on anything relevant on Monday or Tuesday.
As for [22], what I posted on that earlier was preserved in the post that neither Erik
nor you have shown any sign of having read, preferring the small correction which
followed it almost immediately.
[repost from uncorrected post]You may have to find the actual paper. Donk't your university resources work for that?
[end of repost][22] is linked to a mere abstract via Google Scholar, while "View Article" just takes us back
to the article itself! The same goes for [23].
I'll try to Google them on ResearchGate, like I did the reference you gave me next, but the
same thing applies that applies above.
I guess the shortness of the post attracted you like a magnet, causing you
to miss out on the original post, including the following reasoning: >>>
___________________________ first excerpt from the original post_________________
but I don't see any need to be frustrated. Again, from the paper: "Given these observations, it would be reasonable if viviparity in Chaohusaurus
involved a degree of placentation. However, this inference cannot be tested directly with fossil evidence because the
soft tissue is not preserved."
This is the second subset of what I quoted, and is why I find vipers so frustrating.
For all I know, they might be mostly viviparous [which would make the inference "reasonable"]
or all ovoviviparous [which would make the inference almost untenable, given the variety of vipers].
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
======================== end of first excerpt ======================= >>>
And here is why the "Given" is seriously affected:
######################## second excerpt from the original post #####################
From the paper "squamate reproductive strategies are almost bimodally divided between oviparity (egg laying), including
cases of egg retention up to limb-bud stage, and viviparity involving functional placentation, with few
intermediate forms." (Refences cited in the paper)
This is the first subset that I mentioned above.
************************************************************ end of second excerpt
from
https://groups.google.com/g/sci.bio.paleontology/c/X2eRy1wQf8U/m/4I_chwJ8AQAJ
Re: Were Ichthyosaurs Ovoviviparous, or Viviparous?
And, lest your memory fail you between the first repost and the second, compare:
"make the inference almost untenable, given the variety of vipers".
and
"almost bimodally, ... with few intermediate forms."
The second quote would seem to entail that the first quote is wrong.
Have you tried looking at the cited references? Have you searched for a >> review of squamate viviparity?
There has been too little time for that. The whole topic of this thread came
as a brainstorm as I was lying awake this morning around 6 am.
Until then the issue had never occurred to me.
Here's one: https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
Abstract: Squamate reptiles (lizards and snakes) are an ideal model
system for testing hypotheses regarding the evolution of viviparity
(live birth) in amniote vertebrates. Viviparity has evolved over 100
times in squamates, resulting in major changes in reproductive
physiology. At a minimum, all viviparous squamates exhibit placentae
formed by the appositions of maternal and embryonic tissues, which are >> homologous in origin with the tissues that form the placenta in therian >> mammals. These placentae facilitate adhesion of the conceptus to the
uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and >> calcium. However, most viviparous squamates continue to rely on yolk for >> nearly all of their organic nutrition. In contrast, some species, which >> rely on the placenta for at least a portion of organic nutrition,
exhibit complex placental specializations associated with the transport >> of amino acids and fatty acids. Some viviparous squamates also exhibit >> reduced immunocompetence during pregnancy, which could be the result of >> immunosuppression to protect developing embryos. Recent molecular
studies using both candidate-gene and next-generation sequencing
approaches have suggested that at least some of the genes and gene
families underlying these phenomena play similar roles in the uterus and >> placenta of viviparous mammals and squamates. Therefore, studies of the >> evolution of viviparity in squamates should inform hypotheses of the
evolution of viviparity in all amniotes, including mammals.
Thanks, that may be the first paper I look up.
Here's another: https://pubmed.ncbi.nlm.nih.gov/21573966/
There are more, but you can google.
Capice?
This would be a better discussion if you didn't resort to condescension >> so early into it.
This from someone who has treated me with gratuitous condescensionYou have to start letting go of ancient grievances if you actually want
in talk.origins for almost a dozen years, and in sci.bio.paleontology for about
half as long, with two completely contrasting breaks: Thrinaxodon (later nym: Oxyaena) almost
destroying s.b.p with relentless crazy spam, and what I call the Oasis
of Civilization Period, which lasted from mid-2015 to early 2018.
to discuss the science.
But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.
He can't help it. I'm not going to continue with such an edgy exchange.Peter Nyikos
But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.
On Friday, August 26, 2022 at 8:04:19 PM UTC-6, peter2...@gmail.com wrote:
But, on a less aggressive note, the discussion seemed to haveOh no! Sorry… I didn’t mean to start a flame war! (tries to hide his poisonous keyboard behind his back…)
died out until you and Sight Reader came along.
On Saturday, August 27, 2022 at 2:02:33 PM UTC-7, thesigh...@gmail.com wrote:
On Friday, August 26, 2022 at 8:04:19 PM UTC-6, peter2...@gmail.com wrote: >>> But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.Oh no! Sorry… I didn’t mean to start a flame war! (tries to hide his poisonous keyboard behind his back…)
No cause to be sorry, or even concerned. As you've gathered, Peter is a man of very strong opinions, very
forcefully expressed on a very broad range of subjects. He's been here for a long time, and some of this ideas
are very controversial. As a result, discussions often become contentious. Some posters here (and on talk.origins)
get along with him better than others. Stick around, and you'll see why. Open mind, and all that. Unfortunately, it's
been years since any professional paleontologists or even people on that track have been regular participants.
Everybody here is an amateur of whatever grade. John is the closest, as an ornithogist and systematist, Some of the
rest may have advanced degrees in something, but for the most part interest is all we've got in common.
On Saturday, August 27, 2022 at 2:02:33 PM UTC-7, thesigh...@gmail.com wrote: >> On Friday, August 26, 2022 at 8:04:19 PM UTC-6, peter2...@gmail.com wrote: >> > But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.Oh no! Sorry… I didn’t mean to start a flame war! (tries to hide his poisonous keyboard behind his back…)
No cause to be sorry, or even concerned. As you've gathered, Peter is a man of very strong opinions, very
forcefully expressed on a very broad range of subjects. He's been here for a long time, and some of this ideas
are very controversial. As a result, discussions often become contentious. Some posters here (and on talk.origins)
get along with him better than others. Stick around, and you'll see why. Open mind, and all that. Unfortunately, it's
been years since any professional paleontologists or even people on that track have been regular participants.
Everybody here is an amateur of whatever grade. John is the closest, as an ornithogist and systematist, Some of the
rest may have advanced degrees in something, but for the most part interest is all we've got in common.
On 8/27/22 4:05 PM, erik simpson wrote:
On Saturday, August 27, 2022 at 2:02:33 PM UTC-7, thesigh...@gmail.com wrote:
On Friday, August 26, 2022 at 8:04:19 PM UTC-6, peter2...@gmail.com wrote:
But, on a less aggressive note, the discussion seemed to haveOh no! Sorry… I didn’t mean to start a flame war! (tries to hide his poisonous keyboard behind his back…)
died out until you and Sight Reader came along.
No cause to be sorry, or even concerned. As you've gathered, Peter is a man of very strong opinions, veryYou forget Pandora, who admittedly isn't as regular as some.
forcefully expressed on a very broad range of subjects. He's been here for a long time, and some of this ideas
are very controversial. As a result, discussions often become contentious. Some posters here (and on talk.origins)
get along with him better than others. Stick around, and you'll see why. Open mind, and all that. Unfortunately, it's
been years since any professional paleontologists or even people on that track have been regular participants.
Everybody here is an amateur of whatever grade. John is the closest, as an ornithogist and systematist, Some of the
rest may have advanced degrees in something, but for the most part interest is all we've got in common.
On Sat, 27 Aug 2022 16:05:35 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
On Saturday, August 27, 2022 at 2:02:33 PM UTC-7, thesigh...@gmail.com wrote:
On Friday, August 26, 2022 at 8:04:19 PM UTC-6, peter2...@gmail.com wrote:
But, on a less aggressive note, the discussion seemed to haveOh no! Sorry… I didn’t mean to start a flame war! (tries to hide his poisonous keyboard behind his back…)
died out until you and Sight Reader came along.
No cause to be sorry, or even concerned. As you've gathered, Peter is a man of very strong opinions, veryYou are way too charitable. None of of the characteristics you
forcefully expressed on a very broad range of subjects. He's been here for a long time, and some of this ideas
are very controversial. As a result, discussions often become contentious. Some posters here (and on talk.origins)
get along with him better than others. Stick around, and you'll see why. Open mind, and all that. Unfortunately, it's
been years since any professional paleontologists or even people on that track have been regular participants.
Everybody here is an amateur of whatever grade. John is the closest, as an ornithogist and systematist, Some of the
rest may have advanced degrees in something, but for the most part interest is all we've got in common.
describe above inform my responses to the peter's posts.
On Saturday, August 27, 2022 at 10:04:26 PM UTC-7, John Harshman wrote:
On 8/27/22 4:05 PM, erik simpson wrote:
On Saturday, August 27, 2022 at 2:02:33 PM UTC-7, thesigh...@gmail.com wrote:You forget Pandora, who admittedly isn't as regular as some.
On Friday, August 26, 2022 at 8:04:19 PM UTC-6, peter2...@gmail.com wrote: >>>>> But, on a less aggressive note, the discussion seemed to have
died out until you and Sight Reader came along.Oh no! Sorry… I didn’t mean to start a flame war! (tries to hide his poisonous keyboard behind his back…)
No cause to be sorry, or even concerned. As you've gathered, Peter is a man of very strong opinions, very
forcefully expressed on a very broad range of subjects. He's been here for a long time, and some of this ideas
are very controversial. As a result, discussions often become contentious. Some posters here (and on talk.origins)
get along with him better than others. Stick around, and you'll see why. Open mind, and all that. Unfortunately, it's
been years since any professional paleontologists or even people on that track have been regular participants.
Everybody here is an amateur of whatever grade. John is the closest, as an ornithogist and systematist, Some of the
rest may have advanced degrees in something, but for the most part interest is all we've got in common.
Indeed I did. I don't know who Pandora is, or what his/her qualifications are, but I'd be interested to know.
BTW, I described you as a "systematist". Is that correct or would "phylogeneticist" be more accurate? Both?
Christine Janis has also appeared, very irregularly and rarely, but certainly a "pro".
Sorry everyone, Mr. Slow here again (I’m the one for whom the saying, “He who laughs last did not get the joke” was invented)between external egg laying and viviparous birth more of continuum than a hard line.
Anyway, would it be correct to summarize the above as saying that reptiles evolved from true “egg laying” to simply keeping eggs within the body until they “hatched” several times within their history? I guess that would make the difference
Would it be possible for something like Ichthyosaur eggs to evolve “backwards” from a hard reptilian shell egg back to goopy, unshelled, caviar-like blobs of jelly?
All books on paleontology that go into detail about Ichthyosaurs agree that they gave live birth: the fossil evidence for that is overwhelming.
The only ones I've found that discuss what happens before the live birth
are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_, which agree that they were ovoviviparous. Colbert writes:
So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
In contrast, Carroll only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.
Wikipedia's entry simply claims they are viviparous and references an 1846 [NOT 1946] article by J.C. Pearce for it.
In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity. https://en.wikipedia.org/wiki/Viviparity
Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.
Does anyone here have any ideas for other (probably much weaker)
evidence for one form or the other?
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos
If you have access to the following webpage, take a look at Figure 5, which ends with an *early* stage in that web:
https://www.researchgate.net/publication/233720256_Squamate_reptiles_as_model_organisms_for_the_evolution_of_viviparity
Did any ichthyosaur ancestor lay hard shelled eggs?
On Monday, August 29, 2022 at 11:07:40 AM UTC-6, peter2...@gmail.com wrote:
If you have access to the following webpage, take a look at Figure 5, which ends with an *early* stage in that web:
https://www.researchgate.net/publication/233720256_Squamate_reptiles_as_model_organisms_for_the_evolution_of_viviparityDang, I *SO* want to read this thing, but I’m getting absolutely slaughtered at school (to the point that I’m not sure I can make it to the end of the semester without quitting).
Did any ichthyosaur ancestor lay hard shelled eggs?
Oh dang, I never considered this. I assumed their ancestors would be reptiles and therefore lay hard shells, but I never considered whether there might have been reptiles that DIDN’T lay hard shell eggs!
On Friday, August 26, 2022 at 9:39:46 AM UTC-4, peter2...@gmail.com wrote:
All books on paleontology that go into detail about Ichthyosaurs agree that
they gave live birth: the fossil evidence for that is overwhelming.
The only ones I've found that discuss what happens before the live birth are Romer's 1945 text, and Colbert's 1955 _Evolution_of_the_Vertebrates_, which agree that they were ovoviviparous. Colbert writes:
So it is evident that these reptiles were ovoviviparous -- that they retained the egg within the body until it was hatched, as do some modern lizards and snakes. [*ibid*, p. 162]
In contrast, Carroll only has a photo of a fossil of an ichthyosaur giving live birth,
but no mention in the running text about it. The third edition of Benton's text
also makes no mention of the issue.
Wikipedia's entry simply claims they are viviparous and references an 1846 [NOT 1946] article by J.C. Pearce for it.
In a case of the left hand not knowing what the right hand is doing (and vice versa),
the entry on viviparity broadens the meaning of the term and distinguishes four different varieties
among extant animals, giving examples of each kind. One of them is ovoviviparity,
which it seems to want to demote to a variety of oviparity. https://en.wikipedia.org/wiki/Viviparity
Of course, it is difficult if not impossible to decide whether ichthyosaurs were
viviparous or ovoviviparous. It could even depend on the genera.
It is conceivable that some soft tissues could be found preserved in some Konservat-Lagerstätten.
Either bits of fossilized egg membrane (or shell??) or something like an umbilical cord
could tip the scales heavily one way or the other.
Does anyone here have any ideas for other (probably much weaker)
evidence for one form or the other?
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos
Cf sea snakes?
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates. >>>
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Did you use any reference besides the following?latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the
Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
Peter Nyikos
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a
review of viviparity in squamates that reported the egg to be nourished
from outside during "pregnancy". Didn't I cite anything?
latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the
Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you >>>>>> prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a
review of viviparity in squamates that reported the egg to be nourished
from outside during "pregnancy". Didn't I cite anything?
You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones
said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the
Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
[For the definition, see my reply to Daud yesterday.]
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you >>>> prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was aYou did, and here it is:
review of viviparity in squamates that reported the egg to be nourished from outside during "pregnancy". Didn't I cite anything?
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones
said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definitionNote the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer-- http://people.math.sc.edu/nyikos
On Tuesday, September 27, 2022 at 6:02:00 AM UTC-7, peter2...@gmail.com wrote:the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term. >>>> Apparently, retention of the eggs until hatching (or birth, if you >>>> prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a review of viviparity in squamates that reported the egg to be nourished from outside during "pregnancy". Didn't I cite anything?You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones
said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definitionNote the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer-- http://people.math.sc.edu/nyikos
Just as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement.
Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
another example where clarity can't be achieved with a single word.
On Tuesday, September 27, 2022 at 11:12:51 AM UTC-4, erik simpson wrote:
On Tuesday, September 27, 2022 at 6:02:00 AM UTC-7, peter2...@gmail.com wrote:
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term. >>>> Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a review of viviparity in squamates that reported the egg to be nourished
from outside during "pregnancy". Didn't I cite anything?
You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones
said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In
Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer-- http://people.math.sc.edu/nyikos
Just as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement.
This general remark ignores the specific example under question. You have nothing to say about any possible ambiguities in the definition of ovoviviparity given here:that remain in the mother's body until they are ready to hatch."
"Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs
...provide gas exchange."
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).
Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision.
That's not a good use of "even," nor is it a good example of an [alleged] exception.
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
another example where clarity can't be achieved with a single word.
It can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
which I showed to Daud in my reply to him yesterday.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos
PS Here is a much better example: try to show that the word "objective," which Harshman
keeps applying to cladistic classification, is NOT an exception to the general claims
that you have made so confidently above.
I predict you won't even try.
It's been six days, and my prediction at the end is holding up. The default assumption inIn the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
cases like this is that Erik has no good comeback that is aimed at rehabilitating his claims.
Short specific comments in this case follow below.
On Tuesday, September 27, 2022 at 3:23:20 PM UTC-4, Peter Nyikos wrote:
On Tuesday, September 27, 2022 at 11:12:51 AM UTC-4, erik simpson wrote:
On Tuesday, September 27, 2022 at 6:02:00 AM UTC-7, peter2...@gmail.com wrote:
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term. >>>> Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a review of viviparity in squamates that reported the egg to be nourished
from outside during "pregnancy". Didn't I cite anything?
You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though I gave names of genera and higher taxa that encompassed the ones
said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
Harshman has not responded to this "assignment".See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation.
that remain in the mother's body until they are ready to hatch."Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
Erik introduced his claim here:[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer-- http://people.math.sc.edu/nyikos
This statement was rendered vacuous by the following remarks of mine.Just as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement.
This general remark ignores the specific example under question. You have nothing to say about any possible ambiguities in the definition of ovoviviparity given here:
"Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs
provide gas exchange."...
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).
Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision.
That's not a good use of "even," nor is it a good example of an [alleged] exception.
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
another example where clarity can't be achieved with a single word.
It can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
which I showed to Daud in my reply to him yesterday.
Peter NyikosHere is what Erik has no good comeback for:
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos
PS Here is a much better example: try to show that the word "objective," which Harshman
keeps applying to cladistic classification, is NOT an exception to the general claims
that you have made so confidently above.
I predict you won't even try.This prediction put Erik between a rock and a hard place. He has to choose between
loyalty to Harshman and rehabilitating his comments. By his silence, he has chosen loyalty.
Peter NyikosYou can inerpret silence any way you like. I interpret my silence, at least in this case, as simply indicating disinterest.
The on-topic lesson from the largely personal exchange below is thatmaternal nutrients but do not use a placenta. [7] This widespread misuse of the term has led to confusion over what earlier authors meant when using the name. Modern practice has seen the disuse of ovoviviparity in favour of the more specific definitions
the Wikipedia entry on Ovoviviparity seems to be an effort to
rescue the term "ovoviviparous" from its misuse by so many researchers
in the past century. In this way, we can use the term (or one of its shortened spellings)
instead of the less familiar and more cumbersome "lecithotrophic viviparity."
https://en.wikipedia.org/wiki/Ovoviviparity
Excerpt:
Criticisms and disuse
A lack of a rigidly defined term resulted in widespread misuse of the term ovoviviparity in the biological literature.[7] Ovoviviparity has been used to describe delayed forms of egg-laying reproduction as well as live-bearing species that provide
The above notwithstanding, the entry on sea snakes used the term "ovoviviparity" and linked the above webpage.
On Tuesday, October 4, 2022 at 11:28:25 AM UTC-4, erik simpson wrote:the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
On Tuesday, October 4, 2022 at 4:21:06 AM UTC-7, peter2...@gmail.com wrote: >>> It's been six days, and my prediction at the end is holding up. The default assumption in
cases like this is that Erik has no good comeback that is aimed at rehabilitating his claims.
Short specific comments in this case follow below.
On Tuesday, September 27, 2022 at 3:23:20 PM UTC-4, Peter Nyikos wrote: >>>> On Tuesday, September 27, 2022 at 11:12:51 AM UTC-4, erik simpson wrote: >>>>> On Tuesday, September 27, 2022 at 6:02:00 AM UTC-7, peter2...@gmail.com wrote:
Harshman has not responded to this "assignment".On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote: >>>>>>> On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote: >>>>>>>>
Apparently, "ovoviviparous" is ambiguous and not a useful term. >>>>>>>>>>> Apparently, retention of the eggs until hatching (or birth, if you >>>>>>>>>>> prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a >>>>>>> review of viviparity in squamates that reported the egg to be nourished >>>>>>> from outside during "pregnancy". Didn't I cite anything?
You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though >>>>>> I gave names of genera and higher taxa that encompassed the ones
said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In
eggs that remain in the mother's body until they are ready to hatch."Erik introduced his claim here:
Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos
This statement was rendered vacuous by the following remarks of mine.Just as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement.
This general remark ignores the specific example under question. You have >>>> nothing to say about any possible ambiguities in the definition of ovoviviparity given here:
"Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside
does provide gas exchange."...
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).
Here is what Erik has no good comeback for:Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision.
That's not a good use of "even," nor is it a good example of an [alleged] exception.
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
another example where clarity can't be achieved with a single word.
It can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
which I showed to Daud in my reply to him yesterday.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos
PS Here is a much better example: try to show that the word "objective," which HarshmanThis prediction put Erik between a rock and a hard place. He has to choose between
keeps applying to cladistic classification, is NOT an exception to the general claims
that you have made so confidently above.
I predict you won't even try.
loyalty to Harshman and rehabilitating his comments. By his silence, he has chosen loyalty.
Peter Nyikos
Back to a little bit of the personal:
You can inerpret silence any way you like. I interpret my silence, at least in this case, as simply indicating disinterest.
That's Harshman's favorite face-saving fallback too.
From time to time you claim that you are bored with me, but you always come back
sooner or later with personal attacks, especially when I say some nice things about Glenn to you or John.
Aren't you glad I didn't say a nice thing about JTEM the last time I mentioned him to you?
Peter Nyikos
On Tuesday, October 4, 2022 at 4:21:06 AM UTC-7, peter2...@gmail.com wrote:In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]
It's been six days, and my prediction at the end is holding up. The default assumption in
cases like this is that Erik has no good comeback that is aimed at rehabilitating his claims.
Short specific comments in this case follow below.
On Tuesday, September 27, 2022 at 3:23:20 PM UTC-4, Peter Nyikos wrote:
On Tuesday, September 27, 2022 at 11:12:51 AM UTC-4, erik simpson wrote:
On Tuesday, September 27, 2022 at 6:02:00 AM UTC-7, peter2...@gmail.com wrote:
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a review of viviparity in squamates that reported the egg to be nourished
from outside during "pregnancy". Didn't I cite anything?
You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
Harshman has not responded to this "assignment".See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation.
eggs that remain in the mother's body until they are ready to hatch."Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
Erik introduced his claim here:[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer-- http://people.math.sc.edu/nyikos
This statement was rendered vacuous by the following remarks of mine.Just as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement.
This general remark ignores the specific example under question. You have
nothing to say about any possible ambiguities in the definition of ovoviviparity given here:
"Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside
does provide gas exchange."...
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).
Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision.
That's not a good use of "even," nor is it a good example of an [alleged] exception.
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably just
another example where clarity can't be achieved with a single word.
It can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
which I showed to Daud in my reply to him yesterday.
Peter NyikosHere is what Erik has no good comeback for:
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos
PS Here is a much better example: try to show that the word "objective," which Harshman
keeps applying to cladistic classification, is NOT an exception to the general claims
that you have made so confidently above.
I predict you won't even try.This prediction put Erik between a rock and a hard place. He has to choose between
loyalty to Harshman and rehabilitating his comments. By his silence, he has chosen loyalty.
Peter Nyikos
You can inerpret silence any way you like. I interpret my silence, at least in this case, as simply indicating disinterest.
On 10/4/22 9:43 AM, Peter Nyikos wrote:maternal nutrients but do not use a placenta. [7] This widespread misuse of the term has led to confusion over what earlier authors meant when using the name. Modern practice has seen the disuse of ovoviviparity in favour of the more specific definitions
The on-topic lesson from the largely personal exchange below is that
the Wikipedia entry on Ovoviviparity seems to be an effort to
rescue the term "ovoviviparous" from its misuse by so many researchers
in the past century. In this way, we can use the term (or one of its shortened spellings)
instead of the less familiar and more cumbersome "lecithotrophic viviparity."
https://en.wikipedia.org/wiki/Ovoviviparity
Excerpt:
Criticisms and disuse
A lack of a rigidly defined term resulted in widespread misuse of the term ovoviviparity in the biological literature.[7] Ovoviviparity has been used to describe delayed forms of egg-laying reproduction as well as live-bearing species that provide
The above notwithstanding, the entry on sea snakes used the term "ovoviviparity" and linked the above webpage.
In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]On Tuesday, October 4, 2022 at 11:28:25 AM UTC-4, erik simpson wrote:
On Tuesday, October 4, 2022 at 4:21:06 AM UTC-7, peter2...@gmail.com wrote:
It's been six days, and my prediction at the end is holding up. The default assumption in
cases like this is that Erik has no good comeback that is aimed at rehabilitating his claims.
Short specific comments in this case follow below.
On Tuesday, September 27, 2022 at 3:23:20 PM UTC-4, Peter Nyikos wrote: >>>> On Tuesday, September 27, 2022 at 11:12:51 AM UTC-4, erik simpson wrote:
Harshman has not responded to this "assignment".On Tuesday, September 27, 2022 at 6:02:00 AM UTC-7, peter2...@gmail.com wrote:
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
On 9/26/22 6:18 PM, Peter Nyikos wrote:
On 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term. >>>>>>>>>>> Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice.
Afraid I don't remember. If I recall, however vaguely, there was a >>>>>>> review of viviparity in squamates that reported the egg to be nourished
from outside during "pregnancy". Didn't I cite anything?
You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml
HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones >>>>>> said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here.
See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation.
eggs that remain in the mother's body until they are ready to hatch."Erik introduced his claim here:
Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos
This statement was rendered vacuous by the following remarks of mine. >>>> This general remark ignores the specific example under question. You haveJust as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement.
nothing to say about any possible ambiguities in the definition of ovoviviparity given here:
"Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside
does provide gas exchange."...
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).
Here is what Erik has no good comeback for:Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision.
That's not a good use of "even," nor is it a good example of an [alleged] exception.
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably justIt can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
another example where clarity can't be achieved with a single word. >>>
which I showed to Daud in my reply to him yesterday.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos
PS Here is a much better example: try to show that the word "objective," which HarshmanThis prediction put Erik between a rock and a hard place. He has to choose between
keeps applying to cladistic classification, is NOT an exception to the general claims
that you have made so confidently above.
I predict you won't even try.
loyalty to Harshman and rehabilitating his comments. By his silence, he has chosen loyalty.
Peter Nyikos
Back to a little bit of the personal:
You can inerpret silence any way you like. I interpret my silence, at least in this case, as simply indicating disinterest.
That's Harshman's favorite face-saving fallback too.If you would just stop with the crap, people might be more interested in having real discussions with you. As it stands, the nonsense is a
deterrent, as is the tendency to reply to bits 4 or 5 levels deep.
From time to time you claim that you are bored with me, but you always come back
sooner or later with personal attacks, especially when I say some nice things about Glenn to you or John.
Aren't you glad I didn't say a nice thing about JTEM the last time I mentioned him to you?
Peter Nyikos
On Tuesday, October 4, 2022 at 10:08:00 AM UTC-7, John Harshman wrote:
On 10/4/22 9:43 AM, Peter Nyikos wrote:
The on-topic lesson from the largely personal exchange below is that
the Wikipedia entry on Ovoviviparity seems to be an effort to
rescue the term "ovoviviparous" from its misuse by so many researchers in the past century. In this way, we can use the term (or one of its shortened spellings)
instead of the less familiar and more cumbersome "lecithotrophic viviparity."
maternal nutrients but do not use a placenta. [7]https://en.wikipedia.org/wiki/Ovoviviparity
Excerpt:
Criticisms and disuse
A lack of a rigidly defined term resulted in widespread misuse of the term ovoviviparity in the biological literature.[7] Ovoviviparity has been used to describe delayed forms of egg-laying reproduction as well as live-bearing species that provide
oviparity and viviparity.[8]"This widespread misuse of the term has led to confusion over what earlier authors meant when using the name. Modern practice has seen the disuse of ovoviviparity in favour of the more specific definitions of lecithotrophic and matrotrophic
The above notwithstanding, the entry on sea snakes used the term "ovoviviparity" and linked the above webpage.
In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes.[4]On Tuesday, October 4, 2022 at 11:28:25 AM UTC-4, erik simpson wrote:
On Tuesday, October 4, 2022 at 4:21:06 AM UTC-7, peter2...@gmail.com wrote:
It's been six days, and my prediction at the end is holding up. The default assumption in
cases like this is that Erik has no good comeback that is aimed at rehabilitating his claims.
Short specific comments in this case follow below.
On Tuesday, September 27, 2022 at 3:23:20 PM UTC-4, Peter Nyikos wrote:
On Tuesday, September 27, 2022 at 11:12:51 AM UTC-4, erik simpson wrote:Harshman has not responded to this "assignment".
On Tuesday, September 27, 2022 at 6:02:00 AM UTC-7, peter2...@gmail.com wrote:
On Monday, September 26, 2022 at 10:01:49 PM UTC-4, John Harshman wrote:
On 9/26/22 6:18 PM, Peter Nyikos wrote:
Afraid I don't remember. If I recall, however vaguely, there was a >>>>>>> review of viviparity in squamates that reported the egg to be nourishedOn 8/26/22 7:04 PM, Peter Nyikos wrote:
On Friday, August 26, 2022 at 9:09:36 PM UTC-4, John Harshman wrote:
Apparently, "ovoviviparous" is ambiguous and not a useful term.
Apparently, retention of the eggs until hatching (or birth, if you
prefer) requires maternal nourishment of the eggs, at least in squamates.
What is the reasoning/reference behind "Apparently"?
You didn't answer this, even though you used the word twice. >>>>>>
from outside during "pregnancy". Didn't I cite anything?
You did, and here it is:
https://rep.bioscientifica.com/view/journals/rep/147/1/R15.xml >>>>>>
HOWEVER, try as I might, I found no mention of sea snakes, even though
I gave names of genera and higher taxa that encompassed the ones >>>>>> said to be ovoviviparous here:
https://en.wikipedia.org/wiki/Sea_snake#Reproduction
And your second "Apparently" has a big hole in it right here. >>>>>>
See whether you can do any better with it, or with the
other reference you gave:
https://pubmed.ncbi.nlm.nih.gov/21573966/
Did you use any reference besides the following?
https://en.wikipedia.org/wiki/Viviparity
See my replies to Daud and The Sight Reader earlier today as to some reasons why this
reference is suspect. It says this by way of fueling your first "Apparently":
"Ovoviviparity, a less developed form of viviparity, occurs in most vipers, and in most live-bearing bony fishes (Poeciliidae). However, the term is poorly and inconsistently defined, and may be obsolete.[4]
[4] is a 2000 article by Daniel A. Blackburn, *proposing* a change in the terminology:
https://www.researchgate.net/publication/233720323_Classification_of_the_Reproductive_Patterns_of_Amniotes
Blackburn proposed the term "lecithotrophy" to nutrition being provided exclusively by yolk,
with "lecithotrophic oviparity" synonymous with the definition of "oviparity" in the Wiki entry:
"Five modes of reproduction have been differentiated in animals[3] based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation.
Erik introduced his claim here:
Note the reference to [4] again, but Blackburn defines "oviparity" simply as "egg-laying." So it is unclear
whether Blackburn's proposal has been widely adopted.
By the way, Blackburn uses "lecithotrophic viviparity" to give exactly the same unambiguous definition
that the following entry gives to "ovoviviparity":
https://en.wikipedia.org/wiki/Ovoviviparity
[For the definition, see my reply to Daud yesterday.]
Peter Nyikos
Professor, Dept. of Mathematics
University of So. Carolina -- standard disclaimer--
http://people.math.sc.edu/nyikos
This statement was rendered vacuous by the following remarks of mine. >>>> This general remark ignores the specific example under question. You haveJust as a general remark, "unambiguous definitions" in life sciences is as elusive a concept
as any other unqualified statement.
nothing to say about any possible ambiguities in the definition of ovoviviparity given here:
eggs that remain in the mother's body until they are ready to hatch.""Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside
does provide gas exchange."...
"Ovoviviparous animals are similar to viviparous species in which there is internal fertilization and the young are born alive, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body
--https://en.wikipedia.org/wiki/Ovoviviparity
last edited on 15 July 2022, at 07:33 (UTC).
Here is what Erik has no good comeback for:Precision of definitions is great, but life itself is so messy
that exceptions always show up, or have been hanging around. Even "species" defies precision.
That's not a good use of "even," nor is it a good example of an [alleged] exception.
or would leave out or include embarrassing exceptions. Ovip[various letters] is probably justIt can if it is defined in the right way. Your last sentence conveniently ignores the above definition,
another example where clarity can't be achieved with a single word. >>>
which I showed to Daud in my reply to him yesterday.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina at Columbia
http://people.math.sc.edu/nyikos
PS Here is a much better example: try to show that the word "objective," which HarshmanThis prediction put Erik between a rock and a hard place. He has to choose between
keeps applying to cladistic classification, is NOT an exception to the general claims
that you have made so confidently above.
I predict you won't even try.
loyalty to Harshman and rehabilitating his comments. By his silence, he has chosen loyalty.
Peter Nyikos
Back to a little bit of the personal:
You can inerpret silence any way you like. I interpret my silence, at least in this case, as simply indicating disinterest.
That's Harshman's favorite face-saving fallback too.
If you would just stop with the crap, people might be more interested in having real discussions with you.
As it stands, the nonsense is a deterrent, as is the tendency to reply to bits 4 or 5 levels deep.
From time to time you claim that you are bored with me, but you always come back
sooner or later with personal attacks, especially when I say some nice things about Glenn to you or John.
Aren't you glad I didn't say a nice thing about JTEM the last time I mentioned him to you?
Asking Peter to stop with the crap is like asking him not to exhale.Peter Nyikos
And now, back to Ichthyosaurs. They were the most exclusively marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about a fascinating
example that probably spans Mesozoic and Cenozoic: there are several
lines of evidence that coelacanths are, and have been for a long time, ovoviviparous.
On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about a fascinating
example that probably spans Mesozoic and Cenozoic: there are several
lines of evidence that coelacanths are, and have been for a long time, ovoviviparous.
Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote:possible that ovoviviparity was not needed, but economy of hypotheses suggests the strong likelihood that this genus was ovoviviparous also." [p. 199]
On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about a fascinating
example that probably spans Mesozoic and Cenozoic: there are several
lines of evidence that coelacanths are, and have been for a long time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from the Paleozoic.
Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the rest of the week,
but I intend on Monday to go deep into details in a great book on *Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as free-living yolk sac larvae were from a genus, (*Rhabdoderma*) that may have lived in brackish waters rather than the sea. In this case (if the water was less saline than the body tissues) it is
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young, creates the presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote:
On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively marine
reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine
reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea
snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about a
fascinating
example that probably spans Mesozoic and Cenozoic: there are several
lines of evidence that coelacanths are, and have been for a long
time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from
the Paleozoic.
Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the
rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the
Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as free-living
yolk sac larvae were from a genus, (*Rhabdoderma*) that may have lived
in brackish waters rather than the sea. In this case (if the water was
less saline than the body tissues) it is possible that ovoviviparity
was not needed, but economy of hypotheses suggests the strong
likelihood that this genus was ovoviviparous also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young, creates
the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote:
On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine
reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea
snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about
a fascinating
example that probably spans Mesozoic and Cenozoic: there are several >>>>> lines of evidence that coelacanths are, and have been for a long
time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from
the Paleozoic.
Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the
rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the
Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as free-living
yolk sac larvae were from a genus, (*Rhabdoderma*) that may have
lived in brackish waters rather than the sea. In this case (if the
water was less saline than the body tissues) it is possible that
ovoviviparity was not needed, but economy of hypotheses suggests the
strong likelihood that this genus was ovoviviparous also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down the oviduct. All that's needed is for the finished egg to skip that last
step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other molecules.
On 10/6/22 12:05 PM, Peter Nyikos wrote:is possible that ovoviviparity was not needed, but economy of hypotheses suggests the strong likelihood that this genus was ovoviviparous also." [p. 199]
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote:
On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about a fascinating
example that probably spans Mesozoic and Cenozoic: there are several
lines of evidence that coelacanths are, and have been for a long time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from the Paleozoic.
Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the rest of the week,
but I intend on Monday to go deep into details in a great book on *Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as free-living yolk sac larvae were from a genus, (*Rhabdoderma*) that may have lived in brackish waters rather than the sea. In this case (if the water was less saline than the body tissues) it
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young, creates the presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote:
On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively marine
reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea
snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about
a fascinating
example that probably spans Mesozoic and Cenozoic: there are several >>>>> lines of evidence that coelacanths are, and have been for a long
time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from
the Paleozoic.
Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the
rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the
Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as free-living
yolk sac larvae were from a genus, (*Rhabdoderma*) that may have
lived in brackish waters rather than the sea. In this case (if the
water was less saline than the body tissues) it is possible that
ovoviviparity was not needed, but economy of hypotheses suggests the
strong likelihood that this genus was ovoviviparous also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down the oviduct. All that's needed is for the finished egg to skip that last
step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other molecules.
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote: >>>>> On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively
marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea
snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about >>>>>> a fascinating
example that probably spans Mesozoic and Cenozoic: there are several >>>>>> lines of evidence that coelacanths are, and have been for a long
time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from
the Paleozoic.
Sure. What do you have? I presume here that your definition is gas
exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the
rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the
Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as
free-living yolk sac larvae were from a genus, (*Rhabdoderma*) that
may have lived in brackish waters rather than the sea. In this case
(if the water was less saline than the body tissues) it is possible
that ovoviviparity was not needed, but economy of hypotheses
suggests the strong likelihood that this genus was ovoviviparous
also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down
the oviduct. All that's needed is for the finished egg to skip that
last step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other
molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
On 10/12/22 2:13 PM, Trolidan7 wrote:
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote: >>>>>> On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively
marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea
snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk
about a fascinating
example that probably spans Mesozoic and Cenozoic: there are several >>>>>>> lines of evidence that coelacanths are, and have been for a long >>>>>>> time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is
from the Paleozoic.
Sure. What do you have? I presume here that your definition is gas >>>>>> exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the
rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the
Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as
free-living yolk sac larvae were from a genus, (*Rhabdoderma*) that
may have lived in brackish waters rather than the sea. In this case
(if the water was less saline than the body tissues) it is possible
that ovoviviparity was not needed, but economy of hypotheses
suggests the strong likelihood that this genus was ovoviviparous
also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down
the oviduct. All that's needed is for the finished egg to skip that
last step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other
molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
I doubt that small, uncharged molecules notice whether they're going
through a cell membrane or not. I'm pretty sure travel is by passive diffusion, not active transport.
On 10/12/22 2:13 PM, Trolidan7 wrote:
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote: >>>>>> On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively
marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea
snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk
about a fascinating
example that probably spans Mesozoic and Cenozoic: there are several >>>>>>> lines of evidence that coelacanths are, and have been for a long >>>>>>> time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is
from the Paleozoic.
Sure. What do you have? I presume here that your definition is gas >>>>>> exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the
rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth.
It is by Keith S. Thompson, titled _Living Fossil: The Story of the
Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth.
"The Carboniferous fossils that Schultze had described as
free-living yolk sac larvae were from a genus, (*Rhabdoderma*) that
may have lived in brackish waters rather than the sea. In this case
(if the water was less saline than the body tissues) it is possible
that ovoviviparity was not needed, but economy of hypotheses
suggests the strong likelihood that this genus was ovoviviparous
also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down
the oviduct. All that's needed is for the finished egg to skip that
last step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other
molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
I doubt that small, uncharged molecules notice whether they're going
through a cell membrane or not. I'm pretty sure travel is by passive diffusion, not active transport.
On 10/12/22 2:13 PM, Trolidan7 wrote:
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote: >>>>> On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively
marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea
snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk about >>>>>> a fascinating
example that probably spans Mesozoic and Cenozoic: there are several >>>>>> lines of evidence that coelacanths are, and have been for a long >>>>>> time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is from >>>> the Paleozoic.
Sure. What do you have? I presume here that your definition is gas >>>>> exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the
rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth. >>>> It is by Keith S. Thompson, titled _Living Fossil: The Story of the >>>> Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth. >>>>
"The Carboniferous fossils that Schultze had described as
free-living yolk sac larvae were from a genus, (*Rhabdoderma*) that >>>> may have lived in brackish waters rather than the sea. In this case >>>> (if the water was less saline than the body tissues) it is possible >>>> that ovoviviparity was not needed, but economy of hypotheses
suggests the strong likelihood that this genus was ovoviviparous
also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying.
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down
the oviduct. All that's needed is for the finished egg to skip that
last step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other
molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel?
Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when thenI doubt that small, uncharged molecules notice whether they're going
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
through a cell membrane or not. I'm pretty sure travel is by passive diffusion, not active transport.
On 10/12/22 2:33 PM, John Harshman wrote:
On 10/12/22 2:13 PM, Trolidan7 wrote:
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote: >>>>>>> On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively
marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea >>>>>>>> snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk
about a fascinating
example that probably spans Mesozoic and Cenozoic: there are
several
lines of evidence that coelacanths are, and have been for a long >>>>>>>> time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is
from the Paleozoic.
Sure. What do you have? I presume here that your definition is gas >>>>>>> exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the >>>>>> rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth. >>>>>> It is by Keith S. Thompson, titled _Living Fossil: The Story of
the Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth. >>>>>>
"The Carboniferous fossils that Schultze had described as
free-living yolk sac larvae were from a genus, (*Rhabdoderma*)
that may have lived in brackish waters rather than the sea. In
this case (if the water was less saline than the body tissues) it
is possible that ovoviviparity was not needed, but economy of
hypotheses suggests the strong likelihood that this genus was
ovoviviparous also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying. >>>>>
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down
the oviduct. All that's needed is for the finished egg to skip that
last step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other
molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
I doubt that small, uncharged molecules notice whether they're going
through a cell membrane or not. I'm pretty sure travel is by passive
diffusion, not active transport.
O2 has no polar or non-polar side.
A cell membrane is a bilayer generally composed of lipid molecules
along with glycerols and other materials. The lipid has a non-polar
tail that has affinities for other non-polar materials and a polar
side is attracted toward the aqueous polar inside and outside of the membrane.
A cell membrane also has a lot of pores in them that open or close
to allow certain substances in or out. The sodium, potassium, and
calcium channels specific for certain types of ions are some examples.
It might be that CO2 could be different from O2, but you are in
essence saying that all of O2 at least passes through the cell membranes
of the cells of the blood vessels on both sides, and when immune cells
exist the bloodstream they in essence open small doors between the
blood vessel cells, and close those doors behind them?
I was thinking there were regular gaps between the blood vessel cells,
and lymph was formed from a persistent regular leakage from the blood
vessels into the intercellular fluid outside of the blood vessels.
Perhaps that was wrong.
adheres to non-polar fats and a polar (carboxylic acid) side.
On 10/12/22 2:33 PM, John Harshman wrote:
On 10/12/22 2:13 PM, Trolidan7 wrote:
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman wrote: >>>>>>> On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively
marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively
marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea >>>>>>>> snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk
about a fascinating
example that probably spans Mesozoic and Cenozoic: there are
several
lines of evidence that coelacanths are, and have been for a long >>>>>>>> time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is
from the Paleozoic.
Sure. What do you have? I presume here that your definition is gas >>>>>>> exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably the >>>>>> rest of the week,
but I intend on Monday to go deep into details in a great book on
*Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth. >>>>>> It is by Keith S. Thompson, titled _Living Fossil: The Story of
the Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth. >>>>>>
"The Carboniferous fossils that Schultze had described as
free-living yolk sac larvae were from a genus, (*Rhabdoderma*)
that may have lived in brackish waters rather than the sea. In
this case (if the water was less saline than the body tissues) it
is possible that ovoviviparity was not needed, but economy of
hypotheses suggests the strong likelihood that this genus was
ovoviviparous also." [p. 199]
The rationale for this "strong likelihood" would seem to be that
the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth
to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial
source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying. >>>>>
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down
the oviduct. All that's needed is for the finished egg to skip that
last step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other
molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
I doubt that small, uncharged molecules notice whether they're going
through a cell membrane or not. I'm pretty sure travel is by passive
diffusion, not active transport.
I have several more questions about the lymphatic versus the
regular blood circulatory systems that I may have been mistaken
about before.
1, The direction of flow of the lymphatic system is opposite
the flow of the blood circulatory system. Is that correct?
That means that when lymph empties into the regular blood system
at the exit to the lymphatic system, possible backflow of blood
into the lymphatic ducts is stopped by the valves in the lymphatic
system. Since there are many valves in the lymph system, just like
in the blood vessels, failure of one valve will not mean that the
lymph system is not filled because there are many valves within it?
2. I read that in some reptiles there are 'lymph hearts'. Is that
in only some reptiles? Which ones? How about birds? How about monotremes or marsupials? I am thinking that in mammals it is all
skeletal muscles and the fact that the lymph vessels have valves
that make the lymph flow only one way. It does not need to flow
very fast.
3. I remember reading once that mammals have mature red blood cells
with no nucleus. Other vertebrates do not and will retain a nucleus
in mature red blood cells. Why would you think that is so? Small
blood vessels in small animals in the Mesozoic? Resistance to virus infections of the blood? Something else?
On 10/12/22 3:01 PM, Trolidan7 wrote:
On 10/12/22 2:33 PM, John Harshman wrote:
On 10/12/22 2:13 PM, Trolidan7 wrote:
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
On 10/6/22 12:05 PM, Peter Nyikos wrote:
On Tuesday, October 4, 2022 at 6:45:58 PM UTC-4, John Harshman
wrote:
On 10/4/22 2:07 PM, Peter Nyikos wrote:
And now, back to Ichthyosaurs. They were the most exclusively >>>>>>>>> marine reptiles of the Mesozoic,
just as sea snakes in one subfamily are the most exclusively >>>>>>>>> marine reptiles of the Cenozoic.
So it's a bit suggestive [but no more] that, just as those sea >>>>>>>>> snakes are ovoviviparous,
so too the ichthyosaurs might have been.
If either you, Erik, or John shows some interest, I can talk >>>>>>>>> about a fascinating
example that probably spans Mesozoic and Cenozoic: there are >>>>>>>>> several
lines of evidence that coelacanths are, and have been for a
long time, ovoviviparous.
In fact, *Rhabdoderma*, another candidate for ovoviviparity, is
from the Paleozoic.
Sure. What do you have? I presume here that your definition is gas >>>>>>>> exchange across the shell, but no nutrients.
Yes.
I'm busy in talk.origins and other s.b.p. threads for probably
the rest of the week,
but I intend on Monday to go deep into details in a great book on >>>>>>> *Latimeria,*
the living coelacanth and AFAIK the only known Cenozoic coelacanth. >>>>>>> It is by Keith S. Thompson, titled _Living Fossil: The Story of
the Coelacanth_ .
For now, I'll just quote something about that Paleozoic coelacanth. >>>>>>>
"The Carboniferous fossils that Schultze had described as
free-living yolk sac larvae were from a genus, (*Rhabdoderma*)
that may have lived in brackish waters rather than the sea. In
this case (if the water was less saline than the body tissues) it >>>>>>> is possible that ovoviviparity was not needed, but economy of
hypotheses suggests the strong likelihood that this genus was
ovoviviparous also." [p. 199]
The rationale for this "strong likelihood" would seem to be that >>>>>>> the yolk sac, being still attached to the free-swimming young,
creates the
presumption that there had been enough yolk all the way to birth >>>>>>> to dispense with any maternal nutrients in addition.
The alternative hypothesis, that the yolk sac was only a partial >>>>>>> source of nutrition, is less economical, as the author puts it.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of So. Carolina in Columbia
http://people.math.sc.edu/nyikos
Double checking.
For oviparous reptiles, birds, and monotremes, The shell of
an amniote egg is secreted onto an egg during the process of laying. >>>>>>
Therefore an egg that is not laid will have no shell?
Nope. This "process of laying" can take days, as the egg moves down
the oviduct. All that's needed is for the finished egg to skip that
last step of leaving the mother's body.
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other
molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix. I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution. They never
go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
I doubt that small, uncharged molecules notice whether they're going
through a cell membrane or not. I'm pretty sure travel is by passive
diffusion, not active transport.
O2 has no polar or non-polar side.
Actually, O2 is a polar molecule, but not very polar.
A cell membrane is a bilayer generally composed of lipid molecules
along with glycerols and other materials. The lipid has a non-polar
tail that has affinities for other non-polar materials and a polar
side is attracted toward the aqueous polar inside and outside of the
membrane.
A cell membrane also has a lot of pores in them that open or close
to allow certain substances in or out. The sodium, potassium, and
calcium channels specific for certain types of ions are some examples.
It might be that CO2 could be different from O2, but you are in
essence saying that all of O2 at least passes through the cell membranes
of the cells of the blood vessels on both sides, and when immune cells
exist the bloodstream they in essence open small doors between the
blood vessel cells, and close those doors behind them?
I don't know how the immune cells get around, but presumably they don't
go through the epithelial cells but around them.
CO2 is a non-polar molecule, and in fact it's known to diffuse somewhat
more easily than O2.
I was thinking there were regular gaps between the blood vessel cells,
and lymph was formed from a persistent regular leakage from the blood
vessels into the intercellular fluid outside of the blood vessels.
Perhaps that was wrong.
It's been a while since I thought about cellular physiology, and you
might more profitably consult a text.
adheres to non-polar fats and a polar (carboxylic acid) side.
On 10/9/22 11:58 AM, John Harshman wrote:
On 10/9/22 9:57 AM, Trolidan7 wrote:
Is it possible for a blood vessel in a closed circulatory
system to be able to exchange oxygen with a tissue outside
of a blood vessel without also being able to exchange nutrients?
Yes, totally. Oxygen and CO2 diffuse more easily than most other molecules.
When I look up the words 'closed circulatory system' in Wikipedia
it gives three examples - annelids, some molluscs, and vertebrates.
Since two are protostomes and one is a deuterostome I am guessing
that is not based upon phylogenetics.
Now in cephalopods, I am thinking that the copper metalloprotein
that carries oxygen is not contained within any cells inside a
cell membrane, rather it is within a blood matrix.
I am not sure
if the oxygen bound copper diffuses across the blood vessel or not.
Now in vertebrates in general, hemoglobin resides inside red blood
cells. For oxygen to get inside the cells in tissues outside of
blood vessels I am thinking it has to do the following.
Go outside the red blood cell into the extracellular fluid of
the blood in the vessel.
Travel outside the fluid of the blood vessel into the fluid
outside of the blood vessel (sometimes called lymph or other
tissue fluid)
Then go inside of the cells receiving oxygen. There in some
circumstances it might bind with myoglobin for storage before
metabolic use.
During all of this time, both oxygen, nitrogen, and carbon
dioxide remain dissolved in an aqueous solution.
They never go into the gas state. If something like this happens, this
is called the 'bends' (or decompression sickness). This is
generally suppressed because if it becomes too widespread
it can lead to problems with circulation.
Basic question.
In the closed circulatory system of vertebrates, how do
white blood (immune, not red blood) cells go from the
blood vessels into tissues outside of the blood stream
when they undergo some form of damage or infection? Do
they open up small passages in the walls of the blood
vessels and then close them afterward? Are there gaps
that allow them to go through?
How does oxygen or carbon dioxide pass through a blood
vessel? Does it go inside of the cell membranes of the
cells making up the blood vessel walls themselves and
pass through the cells to get inside and outside of the
blood vessels? Does it go through small gaps between
the cells of the blood vessels without passing into and
out of the cells themselves that make up much of the
blood vessel tissues?
Then after that the oxygen or carbon dioxide when then
have to pass through the extracellular fluid of the
tissue before being taken up by the cells in the tissue.
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