A history of land mammals in the western hemisphere

by William Berryman Scott

Section Platyrrhina

III. Hapalidæ. Marmosets.

Hapale. Pleist. and Rec. Midas, Rec.

IV. Cebidæ. South American Monkeys.

Cebus, Pleist. and Rec. Alouatta, Howling Monkeys, Pleist. and Rec. Ateles, Spider Monkeys. Pithecia, Sakis. Cacajao, Uakaris. Nyctipithecus, Douroucoulis. †Eriodes, Pleist. †Homunculus, Santa Cruz. †Pitheculus, do.

The existing Primates are divided into two suborders, Lemuroidea and Anthropoidea, which are quite clearly distinguished from each other, but the fossil forms largely efface the distinction.

Suborder Lemuroidea. Lemurs

The name Lemur, which Linnæus gave to a genus of this suborder, signifies in Latin a spectre or ghost and was probably suggested by the very strange appearance and nocturnal habits of these curious creatures. The term has been adopted as the English name for the group, as there was no vernacular word for it. The lemurs are very obviously the more primitive division of the Primates. Omitting for the present the extinct forms, the dental formula is usually: i 2/2, c 1/1, p 3/3, m 3/3, × 2 = 36; the upper canine is a long, sharp, dagger-like tooth, but the lower one, in nearly all of the genera, is like an incisor and its place is taken by the anterior premolar; the premolars are simple, compressed and trenchant and the upper molars tritubercular. The skull usually has a long and tapering facial portion, so that the living head has some resemblance to that of a raccoon. The orbits almost always have a more or less lateral presentation, instead of being directed forward, as they are in the Anthropoidea; they are encircled in bone, but are not walled in by a bony funnel; the lachrymal bone is extended on the face and the foramen is outside of the orbit. The hind legs are longer than the fore; the humerus retains the epicondylar foramen and the femur has a third trochanter; the feet are plantigrade, almost always five-toed, with opposable thumb and great toe, and having a varying proportion of flat nails and sharp claws. The brain is of a primitive type and not much convoluted.

All the existing and most of the fossil lemurs are small animals, some quite minute, and only in the Pleistocene of Madagascar have large ones been found. They are chiefly nocturnal and arboreal in habits, and feed upon fruit and leaves, but vary their diet with insects, small reptiles, birds and eggs. Their present geographical distribution is very remarkable; more than two-thirds of the existing species are confined to Madagascar; the others are in tropical Africa, southern Asia and the Asiatic islands, as far east as Celebes and the Philippines. In the Eocene epoch they extended all over the northern hemisphere, but have not been found in any subsequent formation outside of their present range.

Lemurs occurred in the Uinta stage, but were much more abundant in the Bridger, of which the best-known genus is †Notharctus. These Eocene forms did not have the aberrant peculiarities of the modern lemurs, but departed less from the primitive stock common to both of the suborders. In †Notharctus the dental formula was: i 2/2, c 1/1, p 4/4, m 3/3, × 2 = 40, the dentition being reduced only to the extent of losing one incisor on each side above and below; the lower canine was not incisiform nor had the anterior premolar taken its place; the upper molars were quadritubercular, and in the lower ones the anterior triangle was hardly higher than the heel. The two halves of the lower jaw were coössified at the symphysis, and the femur had lost the third trochanter. It is not likely that †Notharctus was ancestral to any of the existing lemurs, but may have been to the numerous forms of the European upper Eocene.