pnyikos

I have added sci.bio.paleontology, because Darwin123's contribution is
solidly on-topic there.

Interesting case histories, if true. But these people have a long way
to go before they get good at the evidence.

You, too, "Darwin": why didn't you crosspost this to s.b.p.? We could
sure use more posts like this there.


*Pakicetus,* to be precise. *Ambulocetus* is another transitional
closer to the whales.


*Ambulocetus* is closer and probably *Rodhocetus* [sp.?] is closer
still. Modern whales probably diverged after R. and may even have
diverged after *Zygorhiza* [sp.?], an archaeocete similar to
*Basilosaurus* ["Zeuglodon"] but not too elongated to be a probable dolphin ancestor.

In fact, the evidence for what that LCM looked like is quite scanty,
and transitionals prior to it that are as lovely as Pakicetus for whales are unknown.


This idea of convergent evolution of pinnipedes was once popular but
seems to have fallen out of fashion. Perhaps John Harshman can fill
us in on this one.

In technical terms, you are suggesting that Pinnipedia is
polyphyletic, but the prevailing opinion is that it is monophyletic,
in the sense that the last common ancestor of both seals and sea lions
is believed to have the diagnostic characters of a pinnipede.

Huh? Didn't he say he had become an evolutionism believer?

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

john harshman

Not actually Darwin's hypothesis. He merely presented some observed bear
behavior as a habit that, if continued long enough, might eventually
result is a bear evolving into something rather like a whale. He made no
statement about the relationships of modern whales.


Needless to say (I hope), it's very unlikely that any of these is the
ancestor of any living species. And if they were, we would have no way to tell.


F****vable hyperbole, I suppose. First, nobody has sequenced the genome
of either. We have some pieces of each, and they're more similar to each
other than to other mammals. The bulk of the evidence comes from SINEs.


What we know is that extant pinnipeds are monophyletic, largely due to
molecular evidence. That doesn't mean that they don't have different
terrestrial ancestors, though. It could be (though I doubt it) that
evolved in parallel; but the data have nothing to say about extinct species.

No, in the sense that the last common ancestor is believed
(conclusively) not to have been the ancestor of any other living group
too. We can also make the inference you do, but it's a weaker one.

I'm not sure who "he" is.

pnyikos

This seems a bit noncommittal on your part. The idea Darwin123 was
suggesting was something I read ********ly elsewhere years ago. To
put it in your jargon: "true" seals and Mustelidae were hypothesized
to be in a clade that excludes "eared seals" (sea lions, fur seals, walruses).

You're very protective of the cladists' use of "monophyletic," I
see. Anyway, to put the last thing I said another way: there is a
clade containing bears and "eared seals" but not "true seals"
according to a hypothesis that I once read about somewhere, and
Darwin123 might be thinking of the same hypothesis.

The person Darwin123 addressed as "you": Loribaj.

Peter Nyikos

john harshman

This, as I have clearly explained above, isn't true. Pinnipeds form a
clade with respect to all other extant mammals.

For "the cladists" read "almost everyone, excluding a few holdouts".

I know of no such hypothesis, but it would be false.

Too long an attribution chain to be legible here.

allseeing-i

Whales do not have a land ancestor.

Period.

devils advocaat

Denial of the evidence won't make it go away.

allseeing-i

There is no evidence. Only an interpretation of data and what the
scientists THINK happened.

john harshman

Well, that's settled, then.

steven bornfeld

LOL. Well, if the guy is "all seeing", it's ALL settled then. Let's
all go home. Wait--that's this Saturday, right?

Steve

--
Mark & Steven Bornfeld DDS
http://www.dentaltwins.com
Brooklyn, NY
718-258-5001

tom mcdonald

Same as you?

--
Tom