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RE: Main characters of Dinosauria

Open acetabulum (hip socket): a good observable trait not present in the 
immediate outgroips.
A long deltapectoral crest: the projection on the humerus for a major muscle 

Also, they did NOT die out at 66 Ma. Keep in mind, there aren't any more 
unifying traits to non-avian dinosaurs than there are for
non-bat mammals.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661               

Faculty Director, Science & Global Change Program, College Park Scholars
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 
> Poekilopleuron
> Sent: Tuesday, April 07, 2015 11:37 AM
> To: dinosaur@usc.edu
> Subject: Main characters of Dinosauria
> If you were to explain to lay public a very basic characteristics of (non-
> avian) Dinosauria, which characters would you choose? I would describe it as 
> a large group of archosauromorph reptiles
> living from the middle Triassic (about 235 mya) till the end of the 
> Cretaceous (66 mya). I would make a basic distinction between
> Saurischia and Ornithischia and esp.
> pointing to the paradox that "bird-hipped" dinosaurs are not ancestors of 
> Neornithes. One could also mention three or more sacral
> vertebrae, upright posture, special joint in jaw, thecodontian teeth and many 
> others. Size range from about 100 grams (Anchiornis)
> 100 metric tonnes (titanosaur sauropods). Very effective dual-breathing 
> systém with air sacs, hollow bones in saurischians,
> endo- to gigantothermic metabolism. Vast majority of smaller species (esp. 
> theropods) had a feather-like integument, also known in
> some ornithischians. Cladistic analysis place all living birds into 
> Maniraptora group and are therefore last living saurischian
> dinosaurs. Did I miss something? Thank you very much! Tom =