Thomas Holtz is a dinosaur specialist, renowned for both his research and expository writing on a popular level. Back in the good old days of sci.bio.paleontology, the 1990's, he was a regular participant here.Tyrannosaurus”
Last year, he co-authored a paper in Evolutionary Biology with the formidable title,
Insufficient Evidence for Multiple Species of Tyrannosaurus
in the Latest Cretaceous of North America: A Comment on “The Tyrant Lizard King, Queen and Emperor: Multiple Lines of Morphologicaland Stratigraphic Evidence Support Subtle Evolution and Probable Speciation Within the North American Genus
https://doi.org/10.1007/s11692-022-09573-1
I got access through Academia, with a url that repeats almost the whole title.
The paper is as technical as any I've seen. Perhaps John Harshman can
make immediate sense out of the abstract, whose message is that the authors did not make a good enough case for T.rex having two sister species.
Abstract
The Late Cretaceous dinosaur Tyrannosaurus rex was recently split into three species based on the premise that variation
in the T. rex hypodigm is exceptional, indicating cryptic species and “robust” and “gracile” morphs. The morphs are based
on proportional ratios throughout the skeleton. The species are claimed to be stratigraphically separate, with an early robust
species followed by robust and gracile descendants. There are problems with the hypothesis: the taxon diagnoses are based
on two features that overlap between the species; several skulls cannot be identified based on the diagnoses; proportional
comparisons between Tyrannosaurus and other theropods are based on incomparable samples; the tooth data are problematic;
the stratigraphic framework divides the Hell Creek Formation into thirds, without the stratigraphic position of each
specimen, or independent age control showing the subdivisions are coeval over the entire geographic area; previous work
found variation in T. rex, but it cannot be parsed into discrete categories. We tested for “gracile” and “robust” morphs by
analyzing the femoral and tooth ratios that were published in the multiple species study using agglomerative hierarchical
clustering. The results found that each set of ratios are explained by one cluster, showing that dimorphism is not supported.
We tested for exceptional variation of the femoral ratio of Tyrannosaurus; we calculated the mean intraspecific robusticity
for 112 species of living birds and 4 nonavian theropods. The results showed that the absolute variation in Tyrannosaurus
is unexceptional and it does not indicate cryptic diversity. We conclude that “T. regina” and “T. imperator” are subjective junior synonyms of T. rex.
I've downloaded the paper and will discuss it if there is enough interest.
Peter NyikosI recall Brusatte remarking on how the tooth, snout and jaw structure changes remarkably as the
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
https://people.math.sc.edu/nyikos
On Monday, October 16, 2023 at 2:13:09 PM UTC-7, Peter Nyikos wrote:Tyrannosaurus”
Thomas Holtz is a dinosaur specialist, renowned for both his research and expository writing on a popular level. Back in the good old days of sci.bio.paleontology, the 1990's, he was a regular participant here.
Last year, he co-authored a paper in Evolutionary Biology with the formidable title,
Insufficient Evidence for Multiple Species of Tyrannosaurus
in the Latest Cretaceous of North America: A Comment on “The Tyrant Lizard King, Queen and Emperor: Multiple Lines of Morphologicaland Stratigraphic Evidence Support Subtle Evolution and Probable Speciation Within the North American Genus
https://doi.org/10.1007/s11692-022-09573-1
I got access through Academia, with a url that repeats almost the whole title.
The paper is as technical as any I've seen. Perhaps John Harshman can
make immediate sense out of the abstract, whose message is that the authors
did not make a good enough case for T.rex having two sister species.
Abstract
The Late Cretaceous dinosaur Tyrannosaurus rex was recently split into three species based on the premise that variation
in the T. rex hypodigm is exceptional, indicating cryptic species and “robust” and “gracile” morphs. The morphs are based
on proportional ratios throughout the skeleton. The species are claimed to be stratigraphically separate, with an early robust
species followed by robust and gracile descendants. There are problems with the hypothesis: the taxon diagnoses are based
on two features that overlap between the species; several skulls cannot be identified based on the diagnoses; proportional
comparisons between Tyrannosaurus and other theropods are based on incomparable samples; the tooth data are problematic;
the stratigraphic framework divides the Hell Creek Formation into thirds, without the stratigraphic position of each
specimen, or independent age control showing the subdivisions are coeval over the entire geographic area; previous work
found variation in T. rex, but it cannot be parsed into discrete categories. We tested for “gracile” and “robust” morphs by
analyzing the femoral and tooth ratios that were published in the multiple species study using agglomerative hierarchical
clustering. The results found that each set of ratios are explained by one cluster, showing that dimorphism is not supported.
We tested for exceptional variation of the femoral ratio of Tyrannosaurus; we calculated the mean intraspecific robusticity
for 112 species of living birds and 4 nonavian theropods. The results showed that the absolute variation in Tyrannosaurus
is unexceptional and it does not indicate cryptic diversity. We conclude that “T. regina” and “T. imperator” are subjective junior synonyms of T. rex.
I've downloaded the paper and will discuss it if there is enough interest.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
https://people.math.sc.edu/nyikos
I recall Brusatte remarking on how the tooth, snout and jaw structure changes remarkably as the
young T-rex matures. The changes reported in this paper shows "the absolute variation in Tyrannosaurus
is unexceptional".
erik simpson wrote:Tyrannosaurus”
On Monday, October 16, 2023 at 2:13:09 PM UTC-7, Peter Nyikos wrote:
Thomas Holtz is a dinosaur specialist, renowned for both his research and
expository writing on a popular level. Back in the good old days of sci.bio.paleontology, the 1990's, he was a regular participant here.
Last year, he co-authored a paper in Evolutionary Biology with the formidable title,
Insufficient Evidence for Multiple Species of Tyrannosaurus
in the Latest Cretaceous of North America: A Comment on “The Tyrant Lizard King, Queen and Emperor: Multiple Lines of Morphologicaland Stratigraphic Evidence Support Subtle Evolution and Probable Speciation Within the North American Genus
https://doi.org/10.1007/s11692-022-09573-1
I got access through Academia, with a url that repeats almost the whole title.
The paper is as technical as any I've seen. Perhaps John Harshman can make immediate sense out of the abstract, whose message is that the authors
did not make a good enough case for T.rex having two sister species.
Abstract
The Late Cretaceous dinosaur Tyrannosaurus rex was recently split into three species based on the premise that variation
in the T. rex hypodigm is exceptional, indicating cryptic species and “robust” and “gracile” morphs. The morphs are based
on proportional ratios throughout the skeleton. The species are claimed to be stratigraphically separate, with an early robust
species followed by robust and gracile descendants. There are problems with the hypothesis: the taxon diagnoses are based
on two features that overlap between the species; several skulls cannot be identified based on the diagnoses; proportional
comparisons between Tyrannosaurus and other theropods are based on incomparable samples; the tooth data are problematic;
the stratigraphic framework divides the Hell Creek Formation into thirds, without the stratigraphic position of each
specimen, or independent age control showing the subdivisions are coeval over the entire geographic area; previous work
found variation in T. rex, but it cannot be parsed into discrete categories. We tested for “gracile” and “robust” morphs by
analyzing the femoral and tooth ratios that were published in the multiple species study using agglomerative hierarchical
clustering. The results found that each set of ratios are explained by one cluster, showing that dimorphism is not supported.
We tested for exceptional variation of the femoral ratio of Tyrannosaurus; we calculated the mean intraspecific robusticity
for 112 species of living birds and 4 nonavian theropods. The results showed that the absolute variation in Tyrannosaurus
is unexceptional and it does not indicate cryptic diversity. We conclude that “T. regina” and “T. imperator” are subjective junior synonyms of T. rex.
I've downloaded the paper and will discuss it if there is enough interest.
Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
https://people.math.sc.edu/nyikos
I recall Brusatte remarking on how the tooth, snout and jaw structure changes remarkably as theDid you notice that Brusatte is one of the co-authors of the paper?
young T-rex matures. The changes reported in this paper shows "the absolute variation in Tyrannosaurus
is unexceptional".
We are also told: "Thomas D. Carr and James G. Napoli are co-lead authors."
Here is the whole list:
Thomas D. Carr1 · James G. Napoli2 · Stephen L. Brusatte3 · Thomas R. Holtz Jr.4,5 · David W. E. Hone6 ·
Thomas E. Williamson7 · Lindsay E. Zanno8,9
The numbers refer to information about affiliation, and email addresses
that are on the last page of the article.
It looks as though this paper can take us to the next level of
scholarly criticism. I have read similarly high-level reviews in mathematics,
but this is the first I've seen on such a high plane in paleontology.
Peter Nyikos
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