Anatomy of the temporal bone in early anthropoids, with remarks on the problem of anthropoid origins

New and previously undescribed specimens of the petrous, squamous, and tympanic parts of the temporal bones of anthropoid primates from the Oligocene of Egypt display a general morphological resemblance to the equivalent parts of Recent ceboid skulls. Like that of ceboids, the ectotympanic bone of Fayum anthropoids is a simple anulus, fused to the squamosal at both its extremities. The petrosal's bullar contribution appears to bear transverse septa running laterally from promontory to ectotympanic; similar septa are seen in callitrichids and some prosimians. The definitive stylomastoid foramen is in a position characteristic for ceboids but not found among adult catarrhines. As far as can currently be determined, pneumatization of the petrous and squamous temporal is specifically anthropoid‐like in pattern and extent, but exhibits no special resemblances to that found in any particular anthropoid taxon. On the other hand, Fayum anthropoids appear to resemble other catarrhines and to differ from most extant ceboids in lacking a vascular canal leading from the subarcuate fossa to the sigmoid venous sinus. Vascular impressions on a squamosal fragment tentatively assigned to Aegyptopithecus zeuxis show that the petrosquamous and cranio‐orbital venous sinuses were persistently large, as in prosimians. A squamosal fragment previously attributed to Apidium phiomense , and adduced as evidence for a lemuriform ancestry of Anthropoidea, is probably that of a hyaenodontid creodont. It is certainly not that of a primate. The ceboid like morphology of the early catarrhine ear region is probably primitive for anthropoids, and in any case it does not argue for an Old World origin of ceboids–but it emphatically suggests that Anthropoidea is a strictly monophyletic taxon.