On 8/28/2021 12:25 PM, Oxyaena wrote:

On 8/25/2021 6:20 PM, Peter Nyikos wrote:

When I was at an international topology conference in Baku in 1987,
the shore of the Caspian sea was an easy climb down from our dormitory.
One day as I walked on the beach, I spotted what looked like a skeleton
of a human hand. As I approached, it became clear that the proportions
were wrong.

I can no longer remember whether I realized then that this was from
a flipper of the Caspian seal, or even whether I had read about this seal
before this discovery. One thing is certain: I became quite interested
in this seal and the question of how it got there.

I already knew enough paleogeography to know that, no earlier than the
Pliocene, enough of the great sea Tethys remained for any sea creature
to swim from the Atlantic, through the portion that became the
Mediterranean, thence to the paleo-Black sea, and thence to where
the Caspian Sea is now. It did not surprise me, for instance, to learn
that
there was once a Caspian Sea dolphin, nor that it became extinct
before historical times.

But there is another landlocked seal whose origin is still something
of a mystery:

"It is something of a mystery how Baikal seals came to live there in
the first place. They may have swum up rivers and streams or possibly
Lake Baikal was linked to the ocean at some point through a large body
of water, such as the West Siberian Glacial Lake or West Siberian
Plain, formed in a previous ice age. The seals are estimated to have
inhabited Lake Baikal for some two million years.[7]"
https://en.wikipedia.org/wiki/Baikal_seal

[7] is here:
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1095-8312.2006.00607.x
The enigma of the landlocked Baikal and Caspian seals addressed
through phylogeny of phocine mitochondrial sequences
JUKKA U. PALO, RISTO VÄINÖLÄ, Biological Journal of the Linnean Society >> First published: 27 April 2006

I haven't had time to read the article, but I wish it had been based
more than
just on mitochondrial sequences; these are not as accurate as full genome
sequences.

The timing of events is ultimately to be found elsewhere than in
phylogeny,
but the abstract, which I will be posting in a follow-up to this OP,
makes
it plausible that we can reconstruct events to an accuracy that can
satisfy laymen like myself.


Peter Nyikos
Professor, Dept. of Mathematics   -- standard disclaimer--
University of South Carolina
http://people.math.sc.edu/nyikos

Perhaps this can help elucidate a potential answer: https://peerj.com/articles/9665/

It's a paper describing the discovery of a thousand year old elephant
seal fossil in Illinois. It swam to there via the Mississippi River.
It's not out of the realm of possibility that something similar happened
with the progenitors of the Baikal seal.

No response? For shame, Peter.

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