RE: correct this "definition"

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

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of hammeris1@bellsouth.net
>
> Dougal Dixon writes in his encyclopedia "Complete Book of Dino's":
> 
> Dinosauria:
> The ruling reptiles are characterized by:
> * the number of bones in the skull

For loss of postfrontal bone, perhaps?

> * the presence of a flange on the upper arm bone that held 
> powerful muscles

Dinos are characterized by an enlarged deltapectoral crest, yes.

> * three or fewer finger bones in the fourth finger

Yes.

> * Three or more vertebrae fixed to the hip bones

In general, yes; but either reversed in a few Late Triassic forms or
independantly evolved in Ornithischia, Sauropodomorpha, Theropoda.

> * a hole rather than a socket in the hip for the leg bone

Yes.

> * a small ball-like head on the thigh bone

Subrectangual inturned femoral head. Okay.

> * a strong joint between the foot bones and the bones of the hind leg

By which he means the mesotarsal ankle, maybe? That characterizes a larger
group than Dinosauria. If by this he means a broad (4x wider mediolaterally
than thick anteroposteriorally) metatarsal hinge surface, than yes.

>         Note he has this on his dinosaur classification / tree page,
> but aren't the "ruling reptiles" the archosaurs?   Anyway, if some of
> this is contrary to the current thought on what makes a dino 
> a dino, please point it out.

>  This came out in 2006 and is 
> the most current dino book I've picked up out of the 20 or so I have.

Eh hem...  http://www.geol.umd.edu/~tholtz/dinoappendix, available in stores
and online today... :-)

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
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
http://www.geol.umd.edu/~jmerck/eltsite/
Fax: 301-405-0796

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