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New in Historical Biology

Irmis, R. B., Parker, W. G., Nesbitt, S. J., and Liu, J. 2006.  Early
ornithischian dinosaurs: the Triassic record.  Historical Biology, iFirst
article, 1-20. DOI: 10.1080/08912960600719988


"Ornithischian dinosaurs are one of the most taxonomically diverse dinosaur
clades during the Mesozoic, yet their origin and
early diversification remain virtually unknown. In recent years, several
new Triassic ornithischian taxa have been proposed,
mostly based upon isolated teeth. New discoveries of skeletal material of
some of these tooth taxa indicate that these teeth can
no longer be assigned to the Ornithischia using unambiguous synapomorphies.
The Triassic record of ornithischian dinosaurs
now comprises only three probable occurrences: Pisanosaurus and an unnamed
heterodontosaurid from Argentina, and an
unnamed specimen from the uppermost Triassic of South Africa. This revised
Triassic record suggests that ornithischians
were not very diverse or abundant through the Triassic, and there are large
gaps in the Triassic ornithischian fossil record.
Moreover, traditional living analogues for interpreting the feeding ecology
of early ornithischians from their tooth morphology
are generally inappropriate, and âherbivorousâ archosaur teeth such as
those found in early ornithischians are not necessarily
diagnostic of herbivorous feeding."

Bill Parker
Vertebrate Paleontologist
Division of Resource Management
Petrified Forest National Park
P.O. Box 2217
1 Park Road
Petrified Forest, AZ 86028
(928) 524-6228 x262