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Re: Condylarths again





Eric,
I agree with you that eutherians were still morphologically a relatively undiversified group in the Cretaceous. However, you still seem to be making the assumption that true ungulates (condylarths, artiodactyls, whales, perissodactyls, and the extinct meridiungulates) are the immediate relatives of pseudoungulates (hyraxes, sirenians, aardvarks, and elephants).
Based on mere resemblances you seem to be saying true ungulates and pseudoungulates are sister groups forming a strictly monophyletic (holophyletic) Ungulata, and there is good evidence being found that Ungulata is NOT a holophyletic group, and that many of resemblances between true ungulates and pseudoungulates are convergences (or just plesiomorphies). The proposed close relationship of hyraxes to perissodactyls has been strongly challenged on both morphological and (more recently) molecular grounds.
You yourself remarked how much hyraxes look like guinea pigs (and they look a lot like lagomorph "pikas" too). Most Cretaceous eutherians probably look very much like them or smaller insectivore versions (Insectivora has also been abandoned as polyphyletic).
What I most want you to consider is that several clades probably split off between pseudoungulates and true ungulates, such as Glires (rodents & lagomorphs) and one or more "insectivore" clades-----which would make Ungulata polyphyletic. Even creodonts and carnivores are probably closer to true ungulates than the hyraxes are. And pseudo-hooves (sometimes called nail-hooves) and true hooves probably evolved independently in two separate clades that are not sister groups. Hyraxes are probably closer to rodents than they are to true ungulates!!!
-------Ken Kinman
P.S. The trouble with Condylarthra is that it has a history of being a wastebasket for forms like Tingamarra, thus making it polyphyletic most of the tiame. That is why cladists dislike paraphyletic groups so much (and I totally understand that), but some paraphyletic groups are still useful if you are very, very careful not to use them as wastebaskets. But they are well aware of my views on that, so I will say no more.
********************************************************
From: ELurio@aol.com
To: kinman@hotmail.com, dinosaur@usc.edu
Subject: Re: Condylarths (TINGAMARRA REVISITED)
Date: Mon, 21 May 2001 09:36:31 EDT


In a message dated 5/18/01 10:15:47 PM, kinman@hotmail.com writes:

<<  Hyrax??   You picked a very bad example.  Hyraxes are pseudoungulates
(along with aardvarks, sirenians and elephants), and it is very uncertain
that they are closely related to true ungulates.  So any resemblance you
might imagine between hyraxes and condylarths may be a combination of
plesiomorphies and perhaps some convergence (such as pseudo-hooves vs. true
hooves). >>

Guess what? EVERYTHING was closely related during the Cretaceous!!!! When
last I read [around five years ago, I got a copy of the article somewhere],
it was said that hyraxes were more closely related to prissidactyls than
anything else, making them ungulates.

<<If you want to defend condylarthra as a paraphyletic group, I have no
objection to that, but I only recognize those paraphyletic groups that are
still useful (and I concluded quite some time ago that Condylartha was both
useless and confusing, and the Tingamarra assignment is a perfect example.
I would definitely not use the resemblance to a hyrax (which is probably
rather superficial and/or due to a generalized primitive eutherian
morphotype)...>>

Since you say that condylarthyn resemblance to a hyrax may be due to a
generalized primitive eutherian morphotype, and it's skeleton clearly shows
it to be an ungulate, then it seems to me that hyraxes resemble primitive
ungulates, it "looks like" what a condylarth would.

eric l.
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