Paleobiodiversity, evolution and paleobiogeography of African and Gondwanan Mesozoic vertebrates : contribution of eastern Morocco deposits

Abstract

The evolution of continental vertebrates during the Upper Jurassic and the Jurassic – Cretaceous transition remains poorly known and poorly documented. This is even more striking for the Gondwanan faunas, particularly those of Africa. This is yet a pivotal period, which saw major paleogeographic events and the appearance of major modern clades of terrestrial vertebrates. The discovery of new fossil sites in the Anoual Syncline (Oriental, Morocco), at Guelb el Ahmar (Middle Jurassic) and at Ksar Metlili (Upper Jurassic – Lower Cretaceous), fills these gaps in the fossil record and allows a new perspective on this period.These microvertebrate faunas are the richest and the most diversified ones from the Gondwanan Mesozoic. These two sites have yielded more than 53,000 identified microremains of continental vertebrates. Our systematic study describes and identifies 53 distinct species at Ksar Metlili and 27 at Guelb el Ahmar, including one of the richest associations of micro-mammals in Africa and Gondwana. The faunal lists are revised and augmented with four new mammalian species and three new non-mammalian cynodonts, as well as potential new species of rhynchocephalian lepidosaurs, albanerpetontid amphibians and heterodontosaurid dinosaurs. The rhynchocephalians present at Guelb el Ahmar and Ksar Metlili, as well as the albanerpetontids, could belong to the same evolutionary lineage that persisted in Morocco between the Middle and Upper Jurassic. A preliminary phylogenetic analysis of "dryolestoid" mammals includes for the first time the species of this group described at Ksar Metlili. It suggests that they belong to a monophyletic group, confirming the morphological data, and leads us to classify them within Donodontidae, for which we provide an emended diagnosis. It also suggests that Donodontidae are related to Zatheria, in accordance with the African fossil record, thus renewing the question of the origin of zatherians. This thesis also highligh