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Aardonyx unearthed (was RE: Treason!)



> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of David Marjanovic
>
> A new dinosaur hits the blogosphere before it's reported here!!!
> 
> http://dracovenator.wordpress.com/2009/11/11/earth-claw-is-here/
> 
> To be fair, though, it's reported by the first author 
> himself, so our honor isn't that badly damaged... :-)

Yates, A. M., Bonnan, M. F., Neveling, J., Chinsamy, A. and Blackbeard, M.
G. 2009. A new transitional sauropodomorph dinosaur from the Early Jurassic
of South Africa and the evolution of sauropod feeding and quadrupedalism.
Proc. R. Soc. B doi:10.1098/rspb.2009.1440

Abstract

Aardonyx celestae gen. et sp. nov. is described from the upper Elliot
Formation (Early Jurassic) of South Africa. It can be diagnosed by
autapomorphies of the skull, particularly the jaws, cervical column, forearm
and pes. It is found to be the sister group of a clade of obligatory
quadrupedal sauropodomorphs (Melanorosaurus + Sauropoda) and thus lies at
the heart of the basal sauropodomorph-sauropod transition. The narrow jaws
of A. celestae retain a pointed symphysis but appear to have lacked fleshy
cheeks. Broad, U-shaped jaws were previously thought to have evolved prior
to the loss of gape-restricting cheeks. However, the narrow jaws of A.
celestae retain a pointed symphysis but appear to have lacked fleshy cheeks,
demonstrating unappreciated homoplasy in the evolution of the sauropod
bulk-browsing apparatus. The limbs of A. celestae indicate that it retained
a habitual bipedal gait although incipient characters associated with the
pronation of the manus and the adoption of a quadrupedal gait are evident
through geometric morphometric analysis (using thin-plate splines) of the
ulna and femur. Cursorial ability appears to have been reduced and the
weight bearing axis of the pes shifted to a medial, entaxonic position,
falsifying the hypothesis that entaxony evolved in sauropods only after an
obligate quadrupedal gait had been adopted. 

---------------

Aardonyx skull has graced the title line to Yates' Dracovenator blog for
some time.

It is a cool critter.

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