Re: Extinction - specific info

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

> 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].

The same data (Cathy Forster's dissertation and SVP presentation some years
ago) showed, based on morphometric analysis, that a) hatcheri lies far
outside of the variation found within other Triceratops skulls.  I am
really looking forward to seeing these data published somewhere, so I can
cite them.

> > 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).

I'll let a hadrosaur specialist tackle this one, if they want.  I don't
know enough about the specific differences between the types of the three.
>From what I recall, E. regalis (the type?) is very, very big, E. annectens
(formerly Claosaurus annectens, former type of Anatosaurus) is smaller and
more gracile, and I can't remember what so special about E.
saskatchewanensis.

BTW, for those who were raised on pre-1980s kids dinosaur books, Anatotitan
and Edmontosaurus are the dinosaurs that were called Trachodon for many
years, and Anatosaurus after the 1940s.  If you had a plastic Trachodon
toy, it was Anatotitan copei (based on Charles Knight's classic painting of
the AMNH A. copei pair).

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.