Additional remains of Wadilemur elegans, a primitive stem galagid from the late Eocene of Egypt

摘要

The late Eocene prosimian Wadilemur elegans from the Jebel Qatrani Formation, northern Egypt, was originally interpreted as an anchomomyin adapiform primate based on limited information from the lower molars and distal premolars. Recently recovered fossils attributable to this species, including a proximal femur, the fourth upper premolar and first and second upper molars, and a mandible preserving the lower second premolar and lower canine and incisor alveoli, reveal a number of derived morphological similarities shared with crown strepsirrhines and, in particular, Miocene-to-Recent stem and crown galagids, to the exclusion of known adapiforms. Phylogenetic analysis of 359 morphological features scored across 95 living and extinct crown primate taxa supports a stem galagid placement for Wadilemur and older Saharagalago, and a close relationship between crown strepsirrhines and the Eocene African taxa “Anchomomys” milleri, Djebelemur, and Plesiopithecus (none of which appear to be closely related to European anchomomyins). This scheme of relationships supports the hypothesis that crown Strepsirrhini is of Afro-Arabian origin and that lemuriforms likely colonized Madagascar by crossing the Mozambique Channel. Wadilemur's known dental and postcranial morphology provides additional support for the hypothesis that galagids and lorisids had diverged by the close of the middle Eocene, and, by bolstering the ≈37 million-year-old calibration point for crown lorisiform origins provided by Saharagalago, indirect support for the hypothesis of an ancient origin of crown Strepsirrhini and crown Primates.