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RE: TRICERATOPS AND PSITTACOSAURUS ARE NOT OVERSPLIT
> -----Original Message-----
> From: email@example.com [mailto:firstname.lastname@example.org]On Behalf Of
> T. Mike Keesey
> Sent: Thursday, March 08, 2001 9:14 PM
> To: -Dinosaur Mailing List-
> Subject: Re: TRICERATOPS AND PSITTACOSAURUS ARE NOT OVERSPLIT
> Six species for one genus is not that odd. _Equus_ has 6. _Canis_ has
> about 6. In some schemes, _Ursus_ has 6. _Felis_ has well over 6. I could
> go on for hours.
Furthermore, those are numbers for the Holocene: if you add in just the last
million years or so you can increase those numbers.
Compare this to the probably stratigraphic range for the _Psittacosaurus_
specimens in general (Barremian through Albian, but some possibly earlier)
and you have a LOT of time for speciation.
> It *is* a bit odd for a Mesozoic dinosaur genus (most of which have one
> valid species, if that), true.
But by the same token as above, almost all dinosaur "genera" are known from
a single formation (or, let's face it, from a single quarry...).
Had all _Psittacosaurus_ specimens been found from the same unit from a
limited horizon, I'd suspect that most or all the variation was normal
population variation. However, since these specimens are scattered in time
and space, I suspect that at least some is actual taxonomic variation.
Thomas R. Holtz, Jr.
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
College Park, MD 20742
Phone: 301-405-4084 Email: email@example.com
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-405-0796