Re: Extinction - specific info

[Stan Friesen <swf@ElSegundoCA.ATTGIS.COM>]

 From: Tom Holtz <tholtz@geochange.er.usgs.gov>
 > Hmm, let's see... Even if you lump as far as you can (put both
 > dromaeosaurids as one genus, all the tyrannosaurids as one, take out
 > Dyslocosaurus, put all the Triceratops line [D. hatcheri, T. horridus, and
 > T. sp. 2] as one,

Hmm, what reasoning is behind seperating hatcheri from horridus?

My own perusal of the data seems to indicate that almost all
specimens of Triceratops fall within the range of variation of
a single species in the other genera of ceratopsians.
[I will reserve judgement on T. sp. 2 until I see the paper].

 > both Thescelosaurus forms together, and Anatotitan into
 > Edmontosaurus [although it is clearly a very derived form])

Very derived.

Actually the one aspect of the reclassification of Anatosaurus as
Edmontosaurus that bitehrs me is that three distinct species are
still recognized in *addition* to Anatotitan copei.  They all seem
rather similar to me - and it seems odd that three such similar
species should live simultaneously *and* also last for so long a time
(since at least two of them are also known from pre-Lancian times).

I would think that there would be only one, or perhaps two, species
of Edmontosaurus (not counting Anatotitan).

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.