ملخص: In this paper we report the first occurrence of an endemic African plesiadapiform primate from the early-middle Eocene locality of Glib Zegdou (Hammada du Dra, Algeria). Dralestes (new genus) is a very specialized taxon, and its closest known relative is the enigmatic and controversial genus Azibius from Gour Lazib (Hammada du Dra). We group both together as the Azibiidae (new rank). Dralestes provides the first evidence of the upper dentition in this group. Some critical dental characters, such as a postprotocingulum on upper teeth, consistently reveal a primate status for the azibiids. Dralestes exhibits, however, a very unusual configuration of the upper molars by the enlarged parastyle, the lack of a metaconule, and the ectoloph structure (preparacrista, centrocrista and postmetacrista are aligned in a high blade-like structure). The apparent dental specializations of both lower premolars and molars of azibiids (exaenodonty, large P4 bearing sharp apical cusps, and M1 having a highly elongated trigonid) point to potential relationships with Chronolestes and carpolestid plesiadapiforms. A phylogenetic analysis, performed on 55 dental characters scored for 19 primate genera, clarifies the euprimate status of Altiatlasius, and thus indicates that azibiids are the only known plesiadapiforms from Africa. Azibiids are the sister group of the clade carpolestids/Chronolestes in the superfamily Plesiadapoidea. However, the azibiids differ fundamentally from carpolestids by the combined lack of a centroconule and multiple buccal cusps on P4. The exact position of both Chronolestes and azibiids in the plesiadapoids appears difficult to resolve. A basal position of Chronolestes in this superfamily cannot be ruled out because it exhibits a simple morphology of I1 and no conule on P3. Considering this ad hoc hypothesis, azibiids are found to lie outside a clade including carpolestids/plesiadapids/saxonellids, and they are the sister group to Chronolestes. The clade including the carpolestid, saxonellid, and plesiadapid families is characterized by the occurrence of a centroconule on P3-4. The lack of this trait in Dralestes and Chronolestes could mean that azibiids are basal plesiadapoids that diverged before the evolution of the common ancestor of the three derived plesiadapoid families, i.e. at least around the Paleocene-Eocene boundary or more probably during the Paleocene. The report of the first offshoot in Africa of plesiadapoids enhances the role of Africa in the early primate radiation.

لغة: إنجليزية