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Re: CRAZY S. AMERICAN THEROPODS



At 12:17 PM 7/25/97 +0100, Darren Naish wrote:
>If this animal is based only a foot though (is that correct? I hate all these
>uncertainties), how sure can we be. I guess caution is urged. But that's an
>internet problem - people speculate like crazy on preliminaries. Who cares -
>it's fun;-)

As long as you don't send in a paper for peer review where some of the main
evidence and points of your argument have been (so far) soley restricted to
the internet...  (Grumble, gripe, grumble, get out red pen, grumble...)

>However, suppose Novas's new taxon is a bona fide dromaeosaurid.

Again, and not having been able to decode the image sent, I do not know if
this is the dromaeosaurid, or the troodontid form.  Novas showed a picture
of a sickle-clawed, arctometatarsalian foot at the SVP 96: this might be
Araucanoraptor.  It is not the giant dromaeosaurid: that will be given a
different name, and would be considerably larger than the newspaper article
reports.

>This
>strengthens the case for direct phyletic affinities between S. American forms
>and their northern (putative) relatives. I'm unaware of any recent work on
>_Secernosaurus_,

Hey, Mikey!! :-)

>but am I right in thinking that what's been published on
>_Gasparinisaura_ supports this view too: i.e. because _Gasparinisaura_ is
nested
>within a clade of endemic Laurasian ornithopods, it is more likely to be an
>immigrant from the north rather than a Gondwanan endemic?

Unfortunately, not.  Given the (very basal) position of Gasparinisaura
within Iguanodontia, it could a descendant of a Middle Jurassic Pangaean
fauna rather than a Laurasian immigrant.  (Similar arguments can be made for
the In Abaka dinosaurs of the Barremian of Niger: neither Afrovenator nor
the unnamed sauropod have affinities with dinosaur lineages restricted to
the post-Pangaean north).

>Those of you that may be under the impression that most Gondwanan dinosaurs
seem
>to be descendants of Laurasian invaders, note that much evidence now indicates
>the opposite - i.e. many Laurasian forms may actually be descended from
>Gondwanan invaders. Early oviraptorosaurs

Problematic, but possibly oviraptorosaurs.

>and problematic creatures like
>Gondwanan certopians (is _Notoceratops_ still a ceratopian? There's still the
>Dinosaur Cove 'cf. _Leptoceratops_' ulna) and ornithomimid _Timimus_

Again, problematic.  Some skulls for the "southern oviraptorosaurs" and
_Timimus_ would go a long way into improving our phylogenetic resolution of
these forms.

>throw
>proverbial spanners into the works, and there are more surprises to come yet!

Indeed.

>Does anyone know the current state of play re: S. American ankylosaurs?

Ralph Molnar is working on the systematics of Minmi, which apparently throws
a spanner into the works of basic thyreophoran relationships.  Should be
interesting to see how things fall out (especially with the inclusion of the
"polacanthids" and Tianchisaurus)

>_Albertosaurus_ _Albertosaurus_ _Albertosaurus_. I shall write it out a hundred
>times. 

Except, of course, if you mean "libratus", in which case you've got to write
out _Gorgosaurus_ one hundred times... :-)

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661