RE: Saurischia and Ornithischia pelvis

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

There is no real selective advantage to the forward-pointing pubis: that is 
simply the ancestral condition.

So the two major herbivorous clades approached increasing gut space in 
different ways. Sauropodomorphs simply got bigger and bigger.
Ornithischians moved the pubis backwards, so they could retain a bigger gut 
without size increase.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu         Phone: 301-405-4084
Senior Lecturer, Vertebrate Paleontology
Office: Geology 4106
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Phone: 301-405-9695
Fax: 301-314-9661              

Faculty Director, Science & Global Change Program, College Park Scholars
Office: Centreville 1216
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA 

> -----Original Message-----
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] On Behalf Of 
> Stuart Plotkin
> Sent: Thursday, July 09, 2015 9:16 PM
> To: dinosaur@usc.edu
> Subject: Saurischia and Ornithischia pelvis
> 
> I could use some advice as to what are benefits the forward facing pubic bone 
> in the saurichia vs the rear facing pubic bone in
the
> ornithischia? I was able to determine that the ornithischia pelvis allowed 
> for a larger abdominal area for digestion, but what
about the
> huge sauropod bellies? What selective advantage did these pelvic arrangements 
> give to the two classes of dinosaurs? Thank you