ANTHROPOID PHALANGES FROM THE OLIGOCENE OF EGYPT

Proximal phalanges recovered from Oligocene sediments of the Jebel Qat rani Formation, Fayum Province, Egypt, are attributed to the anthropoi ds Aegyptopithecus and Apidium. A multivariate discriminant function a nalysis using phalangeal shape indices proved reliable for distinguish ing between manual and pedal proximal phalanges of extant primates, an d these data can be applied to classify phalanges of fossil primates. Manual and pedal phalanges of Aegyptopithecus show features clearly re lated to a quadrupedal arboreal lifestyle involving frequent and power ful digital flexion: plantar tubercles are prominent, the flexor sheat h ridges are well developed, shaft height increases proximally, shaft cortices are thickest in their distal halves, and the phalanges displa y strong dorsoventral curvature. Proximal phalanges of Aegyptopithecus resemble those of extant Alouatta, and to a lesser extent those of co lobine primates, in these respects. These fossil phalangeal specimens resemble quadrupedal cercopithecids in having large palmar and plantar tubercles, flaring basal apophyses, robust shafts, and dorsally exten ded and proximodorsally tilted metacarpal and metatarsal facets. Manua l and pedal phalanges of Apidium have straight, robust shafts with cor tices of equal thickness throughout, relatively dorsoventrally compres sed condyles, weak flexor ridges, and a flared base for insertion of t he collateral ligaments and interosseous musculature. These features s uggest a locomotor repertoire for Apidium that is well suited for stab le digital extension during quadrupedal running on horizontal substrat es with little emphasis on grasping capabilities. These features compa re most favourably with those of the phalanges of extant Saimiri.