228 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



(15) The upper and lower molars retain clear traces of derivation from the more primitive almost 

 pure tritubercular type exemplified in the earlier species of Pelycodus, but in Nothardus this lemuroid 

 heritage had been masked by certain csenotelic characters mentioned below (p. 186). 



(16) The vertebral formula was probably C7, D12, L8, S3, Cd?28. The vertebral column exhibits 

 the following primitive lemuroid features: the neck was relatively long as in Lemur, the small dorsal 

 vertebrae indicate a relatively small thorax; the lumbar vertebrse have vertically shallow elongate centra, 

 with wide transverse processes and forwardly directed neur apophyses, as in leaping animals; the sacrum 

 consists chiefly of a large widely expanded vertebra which bore nearly the whole of the articular surface 

 for the ilium, followed by two much smaller vertebrse with widely extended transverse processes; the 

 coccygeal and caudal vertebrse were in general similar to those of Lemur, but less robust. 



(17) The whole forearm is stouter and shorter than that of Lemur, the humerus being especially 

 robust, with marked development of the delto-pectoral and external epicondylar ridges, and a large ento- 

 condyle; the entepicondylar foramen is present. The radius, ulna, and metacarpals are also shorter 

 and stouter than in Lemur. These are probably all primitive lemuroid characters. 



(18) The pelvis is of a very distinctly lemuroid type: the blade of the ilium is short, narrow and 

 projects far in front of the sacrum; its gluteal surface is not flattened and expanded transversely as it is 

 in typical Anthropoidea ; the process for the insertion of the rectus femoris muscle, in front of the ace- 

 tabulum, is very prominent; the ischial tuberosities are little if at all expanded transversely (this indi- 

 cating little if any special fitness for sitting upright). 



(19) The femur is similar to that of Lemur, but the head is more sessile, the great trochanter smaller, 

 and the patellar trochlea has a more prominent external condylar ridge. The tibia and fibula were 

 shorter and more robust than in Lemur. Presumably these are all primitive lemuroid characters, which 

 may indicate a leaping power somewhat inferior to that of Lemur. 



(20) The pes is typically Lewmr-like in the form of the astragalus, calcaneum, and other tarsals and 

 especially in the form of the hallux, a very large powerful digit which was normally set off from the other 

 digits nearly at right angle. The proximal end of the first metatarsal bears a large, long, inwardly directed 

 process for the attachment of the tendon of the peroneous longus muscle. The large distal phalanx of 

 digit I was widely flattened for the support of a broad nail. The metatarsals of digits II-V were much 

 shorter and stouter than those of Lemur, that of digit II being especially short. The proximal phalanges 

 were longer than those of Lemur. It is not certain whether digit IV or digit III was the longest. 



So far as the available evidence indicates, all the above-mentioned characters appear to constitute 

 a primitive lemuroid heritage which has been variously modified in the later lemurs. Notharctus itself, 

 as well as all the other members of the subfamily Notharctinse, are apparently excluded, however, from 

 direct ancestry to modern lemurs by the presence in the upper molars of external intermediate cusps, or 

 mesostyles, and of well-developed posterointernal cusps or pseudohypocones. In Notharctus crassus these 

 specializations are further advanced. Pelycodus, the direct ancestor of Notharctus, has more primitive 

 tritubercular molars, which approach but do not actually reaUze the structural ground plan for all higher 

 primates. 



The nearest known contemporary relatives of the Notharctinse were the Adapinse of the Eocene of 

 Europe, which were probably closely related or directly ancestral to the modern Lemurinse, Chirogaleinse 

 and Megaladapinse, as held by Leche and Forsyth Major. 



As stated above (p. 219) it is quite possible that the New World primates have been derived from 



