GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



227 



TAXONOMIC CONCLUSIONS 



I refer Nothardus to the suborder Lemuriformes rather than to the Neopithecini of Wortman, not 

 primarily because it agrees with all the members of the former assemblage in a few arbitrarily selected 

 structural details (which is a convenient method of analysis that has sometimes led to erroneous con- 

 ceptions of genetic relations) but first because in the general stamp of its skeleton Nothardus is unmistak- 

 ably nearer to Adapts and to the Malagasy lemurs than to any of the Anthropoidea. 



Its lemuroid heritage is indicated in the following palaiotelic lemuroid characters: 



(1) The orbits are guarded posteriorly only by the conjoined processes of the postfrontal and malar, 

 and the orbital fossa is not shut olT from the temporal fossa by a frontal-alisphenoid partition, as it is in the 

 anthropoidea. 



(2) The auditory bulla, formed from the inflated entotympanic bone, covered over the delicate tym- 

 panic annulus, which thus did not form an exposed tympanic spout or ring as it does in the Anthropoidea. 



■ (3) The course of the internal carotid artery (as indicated by the osseous tubes in which its branches 

 coursed) was identical with that of a typical lemur. 



(4) The inflated portions of the opposite buUse were not extended inward toward the mid-line as they 

 are in Tarsius and the Anthropoidea. 



(5) The elongate pterygoid plates of the alisphenoids extended back to the auditory bullje, whereas 

 in the Anthropoidea they are well separated from them. 



(6) In the lower jaw the horizontal ramus was of moderate depth with a well curved lower border, 

 which contrasts with the slender elongate jaw, with a straight lower border, of Lemur. The angle formed 

 a long stout backwardly projecting process, which is variously reduced in recent Lemuroidea and Anthro- 

 poidea. 



(7) The anterior portion of the malar if not in actual contact with the lacrymal certainly came very 

 close to it, whereas in tarsioids and anthroi:)oids it becomes widely separated from the lacrymal and 

 limited to the outer side of the orbit. 



(8) The lacrymal was wholly within the orbit, instead of being widely extended on the face, as it is 

 in modern lemurs; and the lacrymal foramen was marginal, instead of being anterior to the orbit. 



(9) Nothardus, in common with Adapts, retained the high sagittal and lambdoidal crests which 

 are characteristic of primitive placental mammals, but are reduced in modern lemuroids and anthro- 

 poids.^ 



(10) The brain-case was much less expanded than in modern lemuroids and the olfactory chamber 

 was well developed, this indicating a low type of brain. 



(11) The dental formula, l| Ct Pf Mf, is undoubtedly the primitive lemuroid formula. 



(12) The central or inner upper incisors have compressed low crowns, a type which is also repre- 

 sented in Chirogaleus, although somewhat modified in form. The lateral upper incisors had small rounded 

 crowns. 



(13) The lower incisors were spatulate or chisel-shaped, not procumbent and styliform as in modern- 

 ized lemurs. 



(14) The upper and lower premolars were more primitive (more like those of primitive Eocene 

 placental mammals) than are those of any modern lemuroids. 



1 The crests of the gorilla skull are regarded as secondary. 



