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Re: Theropod Forelimb Reduction



Nicholas Renaud wrote:
> After reading the new Raptorex paper, I was wondering if anyone knows of a
> specific reference discussing the hypothesis that forelimb reduction is
> correlated with increasing body size? For example, this trend is
> potentially present in tyrannosaurids in which small forelimbs are a
> result of large body size.

Given that Raptorex was only approximately 3 m long as an adult and has
highly reduced forelimbs, while larger more primitive tyrannosauroids
(Eotyrannus, Guanlong, etc.) have proportionately longer forelimbs, the
new guy actually throws a monkey wrench into this idea. If the reduced
arms of Raptorex represent the same reduction present in Tyrannosauridae,
then it evolved in small body size.

Indeed, the presence of large theropods with big forelimbs (Gigantoraptor,
Therizinosaurus, Deinocheirus, etc.) shows that it is possible to be long
armed and big at the same time.

-- 
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/
Faculty Director, Science & Global Change Program, College Park Scholars
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