A Hand-book to the Primates, Volume 1 (of 2)

by Henry O. Forbes

With regard to the skeleton of Ateles, the lumbar region of the vertebral column is short, and the dorsal segment attains a greater relative length than in any other Ape, being over nine-twentieths of the total length of the spine, without the tail. (Mivart.) The dorsal and lumbar vertebræ together number eighteen. In the tail there are twenty-three vertebræ, flattened on the under side, and exceptionally provided with bony processes, serving as points for the attachment of muscles for rendering it as efficient a prehensile organ as possible. The length of the whole arm and hand in Ateles, in proportion to that of the spine, is 174 to 100; but without the hand it is shorter than the spine, the hand itself being only slightly shorter than the latter. The proportion of the hind-limb to the spine is somewhat less, being 169 to 100. The thumb is reduced to a single metacarpal bone, to which, usually, a single minute nodular phalanx [finger-bone] is articulated, and is completely hidden beneath the integument. Although thus rudimentary and functionless, all its characteristic muscles, except one (the long-flexor) are present. (Huxley.) The upper incisors are unequal, the interior being the larger. There is a space (diastema) between the incisor and the canine teeth (as in all Anthropoidea, except Man); the canines are large and conical; the upper molars large, and their crowns four-cusped, with transverse ridges between the outer and inner front cusps and the outer and inner hind cusps, and also an oblique ridge crossing from the outer front cusp to the inner hind one. In the larynx of Ateles there is a single median air-sac opening from the back of the windpipe, but there is no such extension of the resonating apparatus as is seen in the Howlers (Alouatta). In its brain Ateles exhibits in some respects a higher type than in even the Old World Apes.

In regard to this group of Monkeys, the late Mr. H. W. Bates made the following interesting observations:—"In the Coaitas the tail reaches its highest perfection as a prehensile organ; and on this account it would perhaps be correct to consider the Coaitas as the extreme development of the American type of Apes. As far as we know from living and fossil species, the New World has progressed no further than the Coaita towards the production of a higher form of the Quadrumanous order. The tendency of Nature here has been, to all appearance, simply to perfect these organs, which adapt the species more and more completely to a purely arboreal life; and no nearer approach has been made towards the more advanced forms of Anthropoid Apes, which are the products of the Old World solely. The tail of the Coaita is endowed with a wonderful degree of flexibility. It is always in motion, coiling and uncoiling like the trunk of an Elephant, and grasping whatever comes within reach.... The flesh of the Coaitas is much esteemed by the natives in this part of the country [Obydos, on the Amazon].... One day I went on a Coaita hunt. When in the deepest part of a ravine we heard a rustling sound in the trees overhead, and Manoel [the guide] pointed out a Coaita to me. There was something human-like in its appearance [which is very characteristic of them], as the lean, dark, shaggy creature moved deliberately amongst the branches at a great height. I fired, but unfortunately only wounded it in the belly. It fell with a crash headlong about twenty or thirty feet, and then caught a bough with its tail, which grasped it instantaneously, and then the animal remained suspended in mid-air. Before I could re-load it recovered itself, and mounted nimbly to the topmost branches out of the reach of a fowling-piece, where we could perceive the poor thing, apparently probing the wound with its fingers. Coaitas are more frequently kept in a tame state than any other kind of Monkey. The Indians are very fond of them as pets, and the women often suckle them when young at their breasts.[^[12]] They become attached to their masters, and will sometimes follow them on the ground to considerable distances.... The disposition of the Coaita is mild in the extreme; it has none of the painful, restless vivacity of its kindred, the Cebi, and no trace of the surly, untameable temper of its still nearer relatives, the Mycetes, or Howling-Monkeys. It is, however, an arrant thief, and shows considerable cunning in pilfering small articles of clothing, which it conceals in its sleeping place."

PLATE XXI.

THE VARIEGATED SPIDER-MONKEY.

The Coaitas are like the rest of the Cebidæ, essentially quadrupedal, but they occasionally assume the erect posture. They are purely arboreal in habit, living in small companies in the very high trees of the forest.

Their geographical distribution is very wide. They extend over the whole area of the Cebidæ, i.e., over two of the sub-regions, the Brazilian and Mexican, of the Neotropical Region.

I. THE VARIEGATED SPIDER-MONKEY. ATELES VARIEGATUS.

Ateles marginatus (nec Geoffr.), Humb. Obs. Zool., pp. 340, 354 (1811).

Ateles variegatus, Wagner in Schreb., Säugeth., i., p. 313 (1840); id. Abhandl. Akad. Münch., v., p. 420 (1847); Sclater, P. Z. S., 1870, p. 668; 1871, pp. 39, 225; Gray, Ann. Nat. Hist. (4), vi. (1870), p. 472.