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Re: Condylarths (TINGAMARRA REVISITED)



Eric,
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).
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). When cladistic analysis is done correctly, it can help us uncover such homoplasies that throw us off track. The nail-hooves of hyraxes and true hooves of true ungulates are probably homologous only to the extent that they both evolved from mammalian claws. In other words the character "hooves" should not be regarded as a synapomorphy (although I've seen this done in some textbooks), although you could probably justify nail-hooves as a synapomorphy for pseudoungulates, and true hooves as a synapormorphy for true ungulates.
---------Ken
*****************************************************
From: ELurio@aol.com
Reply-To: ELurio@aol.com
To: kinman@hotmail.com, darren.naish@port.ac.uk
CC: dinosaur@usc.edu
Subject: Re: Condylarths (TINGAMARRA REVISITED)
Date: Fri, 18 May 2001 21:02:25 EDT


In a message dated 5/18/01 11:01:44 AM, kinman@hotmail.com writes:

<< That is why I completely abandoned the name Condylarthra. >>

No. Condylarth is a very good term to describe the ungulates of the K/T
boundry and Paleocene. After all, this was a time when ungulates hadn't
diversified into the current groups. The condylarth ancestors of horses and
whales were, during the Lancian and early Paleocene, far more closely related
to each other than they are to their modern descendants.


Also, since so many on the list are enamored of calling modern birds
dinosaurs and imagining that sparrows are teensy t-rexes, why do you object
to looking at a picture of a hyrax and saying "This is a Condylarth!"

After all, a hyrax LOOKS exactly like a Paleocene condylarth was supposed to
look like.


eric l.
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