RE: Rugops: some questions

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> -----Original Message-----
> From: Nick Pharris [mailto:npharris@umich.edu]
> Sent: Tuesday, June 08, 2004 9:37 PM
> To: tholtz@geol.umd.edu
> Cc: fabdalla@tin.it; dinosaur@usc.edu
> Subject: RE: Rugops: some questions
>
>
> Quoting "Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>:
>
> > That might well be, but they evidence they use to support this
> is the lack
> > of a hierarchical structure within Abelisauroidea that matches any
> > particular break up pattern.
>
> Actually, the phylogeny presented in the
> _Rugops_/_Spinostropheus_ paper is
> consistent with the Africa-first hypothesis:
>
> -ABELISAURIDAE
>   |--Rugops
>   |?-Ilokelesia
>   +--UNNAMED NODE
>       |--Abelisaurus
>       +--CARNOTAURINAE (Rajasaurus + (Majungatholus + Carnotaurus))
>
> Note that ABELISAURIDAE are Pan-Gondwanan, but the interior node
> (Abelisaurus +
> CARNOTAURINAE) is restricted to S.Am. and Indo-Madagascar.  But as Dr. Tom
> noted, we're still a long way from finding everything there is to
> be found.

In point of fact, it is equally consistent with the Africa-first vs. E/W
split hypotheses, because (and here is the important parts):
1) we don't have contemporary abelisaurids from the non-African Cenomanian
(except possibly Ilokelesia)
and
2) we don't have Campano-Maastrichtian abelisaurids from mainland Africa.

IF the latter were discovered, and these consistently fell outside the
Abelisaurus + Carnotaurinae clade, THEN we'd have support for Africa-first.
But since we don't have those yet, the phylogeny discovered is equally
consistent with both break-up scenarios.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796