[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Austrocheirus isasii - new Late Cretaceous abelisauroid

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of David Marjanovic
> Brad McFeeters wrote:
> > > The evidence provided here suggests that the strong 
> reduction of the 
> > >foreli=  mb recorded in derived abelisaurids is not directly 
> > >correlated with their i=  ncreased body-size=2C but it 
> seems to be an 
> > >evolutionary event exclusive to=  this lineage within 
> Ceratosauria."
> > >=20
> >
> > So is _Limusaurus_ no longer classified as a ceratosaur=2C 
> or does its 
> > fore= limb not qualify as "strongly reduced"?
> *Limusaurus* was probably published while *Australocheirus* 
> was in press or in review.
> Of course, by being small and nonetheless having reduced 
> forelimbs, it supports the same point that forelimb reduction 
> and increased body size aren't perfectly correlated among 
> ceratosaurs.

Ezcurra et al. do include Limusaurus in their analysis. It, Austrocheirus,
Elaphrosaurus, and the "noasaurids" wind up in the strict consens to form a
polytomy relative to Abelisauridae. (In individual MPTs, Limusaurus is
either sister to Elaphrosaurs or to Masiakasaurus). As they point out,
Masiakasaurus may have short forelimbs, but the enlarged manual claw (also
in Ligabuenio and Noasaurus) shows that they are not as atrophied as in
Limusaurus and abelisaurids. What is known of the hand of Austrocheirus is
comparable to Ceratosaurus, and thus they infer that the extreme reduction
in Limusaurus and in Abelisauridae is convergent and non-basal to

(And, of course, this reinforces the idea that the manual condition of
Limusaurus may not be terribly useful in identification of homologies and
transformations in the lineage leading to birds).

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