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Main » 2008»July»5 » THE OLDEST AFRICAN CROCODYLIAN: PHYLOGENY, PALEOBIOGEOGRAPHY, AND DIFFERENTIAL SURVIVORSHIP OF MARINE REPTILES THROUGH THE CRETACEOUS-TERTIA
THE OLDEST AFRICAN CROCODYLIAN: PHYLOGENY, PALEOBIOGEOGRAPHY, AND DIFFERENTIAL SURVIVORSHIP OF MARINE REPTILES THROUGH THE CRETACEOUS-TERTIA
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A gavialoid crocodylian from the Maastrichtian of the Oulad Abdoun phosphatic Basin (Morocco) is described, representing the oldest known crocodylian from Africa. The specimen consists of a skull that exhibits several features not found in other gavialoids, and a new genus and species is erected, Ocepesuchus eoafricanus. A phylogenetic analysis has been conducted including 201 characters and 71 taxa, where Ocepesuchus eoafricanus appears as the most basal African gavialoid, and the South American gavialoids are paraphyletic. This paraphyly has strong biogeographic implications, and the previous hypothesis of South American and Asian assemblages derived from African gavialoids should be reviewed. The historical biogeography of Gavialoidea is probably more complex than previously supposed. The phosphatic deposits of Morocco provide a unique opportunity to study the vertebrate faunal turnover across the Cretaceous- Tertiary (KT) boundary. The crocodyliforms are very scarce in the Maastrichtian marine basins of Africa which are dominated by mosasaurid squamates. The latter became extinct by the KT boundary, while crocodyliforms survived and diversified in the Paleocene. Mosasaurids and crocodyliforms both lived in probably comparable marine environments during the Maastrichtian. The selectivity of the KT boundary extinctions remains to be explained; since freshwater environments are known for having been less affected by the KT crisis than marine ones, a freshwater lifestyle of the juveniles, like in extant marine crocodiles and unlike the fully marine mosasaurs, could explain this difference with regard to survivorship.
Ocepesuchus eoafricanus nov. gen. et sp., holotype, OCP DEK-GE 45, from the Maastrichtian of Morocco. Reconstruction of the holotype cranium in dorsal view. Fit of the most parsimonious cladogram (consensus) to the stratigraphic and geographic distribution. The boxes show the reconstructed paleobiogeographic history of gavialoids, according to the most parsimonious phylogeny.
