Abelisauridé d'Egypte

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Posté par Lolo il y a 18 ans

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Smith, J. B., & M. C. Lamanna. 2006. An abelisaurid from the Late
Cretaceous of Egypt: implications for theropod biogeography.
Naturwissenschaften 93 (5): 242-245.

"Recent paleogeographic scenarios postulate the isolation of
continental Africa during the Late Cretaceous. The absence of
abelisaurid theropods from Upper Cretaceous African strata was
offered as support of hypothesized African isolation with the
acknowledgement that the paucity of African abelisaurids may be
mostly an issue of sampling. Here we report on a shed theropod tooth
from the Upper Cretaceous (Maastrichtian, ~70 Ma) Duwi Formation of
Egypt. The tooth was referred to the Malagasy abelisaurid
“Megalosaurus” crenatissimus (=Majungasaurus crenatissimus) in 1921.
A discriminant function analysis was run to test for morphological
congruence between the Egyptian tooth and the dentitions of 24
theropod taxa. The analysis correctly classified 96.6% of the teeth
in the sample and assigned the tooth to Majungasaurus. As current
paleogeographic reconstructions posit Madagascar had attained its
current position relative to Africa before the Late Cretaceous, it is
unlikely that the Egyptian tooth actually pertains to Majungasaurus.
Nevertheless, its classification as an abelisaurid supports its
referral to the clade. This tooth thus constitutes defensible
evidence of an abelisaurid from the post-Cenomanian Cretaceous of
mainland Africa. Combined with recent discoveries of abelisaurids in
Niger and Morocco, the result indicates that Abelisauridae was a
diverse group in Africa during the Cretaceous, existing in multiple
places for at least ~25 Ma and weakens support for hypotheses of an
isolated Africa during the Late Cretaceous.