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To Lump or Not To Lump?




Although I tend to be a lumper myself, overlumping can be just as bad as oversplitting. The lumping of Triceratops into two species seems to be a good middle ground. A little premature to lump all of them into one just because sexual dimorphism is a "possibility", and it could end up going back the other way (one or two lumped species may have to be "unlumped" in the future). And likewise, a half dozen or so Psittacosaurus species sounds about right. Moderation in all things.
With unusual brevity, Ken
*********************************************************
From: Dinogeorge@aol.com
Reply-To: Dinogeorge@aol.com
To: dinosaur@usc.edu
Subject: Re: (no subject)
Date: Mon, 12 Mar 2001 12:45:27 EST

In a message dated 3/12/01 11:49:20 AM EST, Tetanurae@aol.com writes:

<< Additionally, I think youre still not understanding the point I was trying
to make. The very, very large range in Asia that psittacosaurs lived in,
as well as the probably very extensive temporal range that psittacosaurs
lived demonstrates that they didn't all live together and weren't competing
directly. In fact, you'd be hard pressed to find two species of
Psittacosaurus
that even SAW each other alive, save for P. sinensis and P. youngi. 
Insisting
that all the various species of Psittacosaurus must be lumped into one or
two
is like insisting that all the various fossil equids in North America must
be
lumped into one or two equid species because they lived in North America and
lived during the Cenozoic. >>


I strongly suspect that if the fossil record were more complete, we would see
>at least< this kind of diversity for practically all the genera of smaller
dinosaurs, and close to this kind of diversity for the genera of larger
dinosaurs, too. The diversity of the very largest dinosaurs, however, would
probably not be much greater than what we already know, since the sampling of
the fossil record is heavily biased toward forms the leave large fossils.
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