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RE: Question about hominids (from 'Ardi')

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of Box, Rick
> Last night on the 'Ardi' special on Discover, a professor 
> from Kent State (Owen Lovejoy) talked about how hominids' 
> bipedal locomotion was unique in the animal kingdom.
> I understand that birds have the 'backwards knee' that's 
> really their ankle that makes how they walk different from 
> us, but tyrannosaurids and hadrosaurids, and other dinosaurs, 
> had the forward knee - how is their locomotion different from 
> hominids?
> I'm especially curious because somebody on the show (can't 
> remember who) made the claim that bipeds are going to be less 
> agile and less speedy than quadrapeds. Wouldn't most 
> tyrannosaurids disagree?
> Could somebody show a dilettante some love? 

Two explanations come to mind:

1) Hominid worker forgets the diversity of life outside of primates, or
placental mammals, or something along those lines...

2) (More generous explanation) Most bipeds, including dinosaurian ones, are
balanced with their vertebral column essentially horizontal relative to the
ground. Hominids are unusual (not unique: e.g., penguins) in having their
vertebral column oriented perpendicular to the ground.

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, Earth, Life & Time Program, College Park Scholars
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