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Noasaurid claws


Agnolin, F.L. & P. Chiarelli. 2009. The position of the claws in Noasauridae
(Dinosauria: Abelisauroidea) and its implications for abelisauroid manus
evolution. Paläontologische Zeitschrift Online First. DOI

Abstract  In this note we reassess the position of putative pedal phalanges
of some South American noasaurid theropods (Abelisauroidea). Noasaurids were
considered as to be distinctive abelisauroids with a peculiar ?sickle claw?
on the second toe of the foot, convergently developed with that of
deinonychosaurians. Among noasaurids, the Argentinean species Noasaurus
leali (latest Cretaceous) and Ligabueino andesi (Early Cretaceous) are known
from incomplete specimens, including dissarticulated non-ungueal phalanges,
and, in N. leali, a claw. A detailed overview of these elements indicates
that the supposed raptorial claw of the second pedal digit of N. leali
actually belongs to the first or second finger of the manus, and the
putative pedal non-ungual phalanges of both genera also pertain to the
manus. Thus, the new interpretations of noasaurid pedal morphology blur the
distinctions between Noasauridae and Velocisauridae proposed by previous
authors. Finally, we suggest, on the basis of phalangeal and metacarpal
morphology, that abelisaurids probably lost their manual claws by means of
the loss of function of the HOXA11 and HOXD11 genes. Thus Noasauridae
differs from Abelisauridae in retaining plesiomorphic long forelimbs with
well developed claws, as occurs plesiomorphically in most basal theropods
(e.g., Coelophysis).

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