ABELISAUROID DINOSAURS FROM THE EARLY CRETACEOUS OF LIBYA

Despite intensive sampling, Cretaceous terrestrial vertebrates from continental Africa remain rather poorly known, frustrating efforts to better understand Gondwanan paleobiogeography and terrestrial African paleoenvironments during the interval. This is especially true of Libya, which has an extremely poor record of Cretaceous terrestrial vertebrates. However, recent discoveries from Lower Cretaceous rocks in the Jabal Nafusah region are significant. Foremost among these are a tooth from the Chicla Formation (Aptian-Albian, ~125-99 Ma), referable to the prominent theropod dinosaur clade Abelisauridae, and associated vertebrae and hindlimb elements of a large-bodied dinosaur from the Cabao Formation (early Aptian, ~125-120 Ma), referable to the widespread ceratosaurian clade Abelisauroidea. The discoveries add to the growing record of abelisauroids from mainland Africa, and firmly establish the clade on the continent prior to its final separation from South America. Indeed, the age of the Cabao theropod (among the oldest known definitive abelisauroid occurrences) predates or is penecontemporaneous with the accepted timing of fragmentation of most major Gondwanan landmasses, supporting the hypothesis that abelisauroids could have dispersed throughout the southern continents before land connections between these areas were severed. Moreover, the considerable size of this theropod (comparable to some coeval spinosaurids and carcharodontosaurids) challenges assertions that abelisauroids were ecologically subordinate to basal tetanuran theropods in Gondwanan Early and “middle” Cretaceous paleoenvironments.