Skull of Megalohyrax eocaenus (Hyracoidea, Mammalia) from the Oligocene ofEgypt

The cranial anatomy of Megalohyrax eoceanus Andrews, 1903, a pliohyracid (H yracoidea, Mammalia) from Oligocene levels of the Jebel Qatrani Formation o f the Fayum Depression in Egypt, is described. Megalohyrax is the largest o f the Fayum hyracoids, its skull is 391 mm long and the specimen described here is probably the best-preserved pliohyacid skull known. Megalohyrax has a strong lambdoid crest, a primitive alisphenoid canal, a notch for the mi nor palatine neurovascular group, orbits which are not anteriorly displaced , and a broad contact between the maxilla and frontal. In all of these feat ures, Megalohyrax differs from modem hyracoids. Contrary to previous sugges tions, the dental formula of Megalohyrax is 3.1.4.3, not similar to early s irenians (which have 5 premolars). Basioccipital morphology suggests that M egalohyrax may have had a eustachian sac.