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Encyclopedia Britannica - Main :: CHA-CHR |
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CHIN and SQUIRREL-MONKEY). The second section of the sub-family includes the spider-monkeys (fig. 13), and is characterized by the completely prehensile tail, with the inner surface of the tip naked, the rudimentary condition or absence of the thumb, the laterally compressed and more or less pointed nails, and the absence of an entepicondylar foramen to the humerus. The limbs, too, are very long and slender, with the front pair of greater length than the hind ones. The caecum approximates to that of the Catarrhina, having its terminal extremity pointed. The true spider-monkeys (Aides) lack the thumb, and have the nails but slightly compressed and pointed, the limbs very long, the nasal septum of ordinary width, and the fur not woolly. Nearly all have the hair on the head, except that of the forehead, directed forwards. There are nearly a dozen species. In these monkeys so powerful is the grasp of the tail that the whole body
than usual. In the woolly spider-monkeys of the genus Lagothrix (fig. 14) not only is the fur woolly, but the thumb is fairly well developed; the nails are like those of Brachyteles, but the nostrils are normal. Humboldt's spider-monkey, L. humboldti (or L. lagotrica) and the dusky spider-monkey, L. infumata, both of which occur in Brazil and Amazonia, alone represent this genus. Some half-dozen species of the monkeys known as sakis (Pithecia) form the typical representatives of the sub-family Pithecinae, in which the tail, even when long, is non-prehensile, while the lower incisors are slender and inclined forwards in a peculiar manner, with a gap on each side separating them from the long canine. The hemispheres of the brain cover the cerebellum, the brain-case is elongated, and, despite the absence of a laryngeal sac, the lower jaw is deep with a large angle, thus recalling that of the howlers. There is no caecum. In all cases the thumb is well developed. The arrangement of the hair is very variable. From the other members of the group the sakis are sufficiently distinguished by the long and bushy tail; while they are further characterized by having a large head. In some cases the hair on the crown of the head is divided by a transverse parting, so as to overhang the upper part of the face. P. satanas of Para and P. chiropotes of Guiana are well-known species. The uakaris (Uacaria or Cothurus) of Amazonia are broadly distinguished from all other Cebidae by their short or rudimentary tails; Ua. calva being remarkable for its brilliant red jaw and pale chestnut hair (see UAEARI). with more forwardly directed eyes, which are not surrounded by a radiating fringe of hair and a wider nasal septum. The titis are-represented by about ten species, of which C. moloch is represented in fig. 16. Most of them are confined to Amazonia, but a few h t t Like t tamong tem . mooc, reace ea coa . e marmoses, The last and lowest representatives of the Cebidae constitute the sub-family Nyctipithecinae, the members of which are cat-like monkeys, with woolly or bushy hair, short, conical muzzles, non-prehensile tails and well-developed thumbs. The brain-case of the skull is not elongated, and the hemispheres of the brain do not cover the cerebellum. The lumbar vertebrae are elongated, with long, sharp
long and hooked caecum has its terminal portion constricted. In accordance with their nocturnal habits, the douroucoulis (Nyctipithecus) are easily recognized by their large and closely approximated eyes, which are, however, separated by a complete septum, the comparatively narrow nasal septum, small ears buried in the woolly fur, and long bushy tail. Well-known species are the lemur-like douroucouli (N. felinus, fig. 15) of Amazonia, Peru and Ecuador, and N. vociferans, with a nearly similar distribution. The titis, Callithrix (or Callicebus I), are smaller monkeys (fig. 16), Apparently the name Callithrix was originally given to the marmosets, and if transferred to that group should be replaced by Callicebus.lower canines are not markedly larger than the incisors constituting the typical Hapale, while such as have the lower canines taller than the teeth between them form the genus Midas. These squirrel-like little monkeys, in which the great toe can be opposed to the other toes, range as far north as 15 N., where they are represented by Midas geoffroyi, and as far in the opposite direction as the southern tropic, where M. chrysopygus and M. rosalia occur. The colour and the length of the hair are very variable, some species having long silky pale-chestnut hair (fig. 17) and tufted ears, while in others the hair is comparatively short and black, or black with brown bars, while the ears are not tufted (see MARMOSET). Lemurs, Prosimiae.-Although the likeness generally takes the form of a more or less grotesque caricature, the faces of all monkeys and apes present, in greater or less degree, some resemblance to the human countenance. In the lower group of Primates, commonly known as lemurs, or lemuroids, this resemblance is wholly lost, and the face assumes an elongated and fox-like form, totally devoid of that " expression" which is so characteristic of man and the higher apes and monkeys. uc, Upper canine. pm, Premolars. lc, Lower canine. m, True molars. Lemurs, Prosimiae or Lemuroidea, which form a group con-fined to the tropical regions of the Old World and more numerously represented in Madagascar than elsewhere, are arboreal and for the most part crepuscular or nocturnal Primates, feeding on insects or fruits, or both together and collectively characterized as follows. The tail, which is generally long and thickly haired, is never prehensile. As a rule, there is a single pair of pectoral teats, but an additional abdominal or even inguinal pair may be present. The thumb and great toe are opposable to the other digits, the former being provided with a flat nail, while the second toe is always furnished with a claw; the fourth toe is longer than all the rest, and the second, or index, finger
they feed largely upon insects and grubs. Platyrrhina is represented The second and last family of the by the marmosets or oustitis (Hapalidae), all of which are small monkeys, with the ears hairy externally, and nails, except that the of the great toe, claw-like, the thumb non-opposable, the tail long, bushy and non-prehensile, and only two molars in each jaw, the dental formula
has no entepicondylar foramen. Three young are produced at a birth
formula
birth
The distribution of existing lemurs is very peculiar, the majority of the species inhabiting Madagascar, where they for the most part dwell in small patches of forest, and form about one-half the entire mammalian fauna of the island. The remaining species inhabit Africa south of the Sahara and the Indo-Malay countries. Tarsier.The tiny little large-eyed Malay lemuroid known as the tarsier, Tarsius spectrum (or T. tarsius), of the Malay Peninsula and islands, together with its Celebean and Philippine representatives, alone constitutes the section Tarsiina (and the family Tarsiidae), which has the following distinctive characteristics: The lower incisor is vertical and the canine of normal form, while the upper incisors are in contact; the orbit is cut off from the temporal fossa by a bony plate, leaving only a small orbital fissure; the tympanum enters into the formation of the auditory meatus, through which passes the canal for the internal carotid artery; the tibia and fibula in the hind-leg are fused together, and the calcaneum and navicular of the tarsus elongated. The tarsier seems to be a primitive form which makes a certain approximation to the Anthropoidea, and differs from other lemuroids, in the structure of its placenta. The dental formula is i. , c. }, p. 8, m. total 34. Tarsiers have enormous eyes, occupying the whole front of the orbital region, and are purely nocturnal in their habits, living in trees on the branches of which they move by hopping, a power they possess owing to the elongation of the tarsal bones (see TARSIER). Malagasy Lemurs.All the other Prosimiae may be grouped in a second section, the Lemurina, characterized as follows: The lower incisors and the canine are similar in form and inclined forwards (fig. 18) ; the upper incisors are small and separated by an interval in the middle line; the orbits communicate largely with the temporal fossae; the internal carotid artery enters the skull in advance of the auditory meatus through the foramen lacerum anterius; and the tibia and fibula are separate. The Malagasy lemurs are now all included in the single family Lemuridae, which is confined to Madagascar and the Comoro Islands, and characterized by the tympanic ring lying free in the auditory bulla. The typical sub-family Lemurinae, which includes the majority of the family group, is characterized by all the fingers except the index having flat nails, the elongation of the facial portion of the skull, the large hemispheres of the brain not covering the cerebellum, the occasional presence of two inguinal in addition to the normal pectoral teats, the dental formula i. , c. p. m. y, with the first upper incisor generally small and sometimes wanting, and the hinder cusps of the upper molars smaller than the front ones. These lemurs are woolly-haired animals, often nearly as large as cats, with the legs longer than the arms, the tail long and bushy, and the spinal processes of the last dorsal and the lumbar vertebrae inclined. In the typical genus Lemur (fig. 19), the tarsus is of normal length, the tail at least half as long as the body
In all these lemurs the small upper incisors are not in contact with one another or with the canine, in front of which they are both placed. In the species of Hapalemur, on the other hand, the upper incisors are very small, sub-equal and separated widely in the middle line; those of each side in contact with each other and with the canine, the posterior one being placed on the inside, and not in front of the latter. Muzzle very short and truncated. Two inguinal teats, in addition to the normal pectoral pair, are present. The last premolar is broader than those in front, and the upper molars lack a distinct cingulum. The typical H. griseus is smaller than any of the true lemurs, of a dark-grey colour, with round face and short ears. It is quite nocturnal, and lives chiefly among bamboos, subsisting on the young shoots. The second species has been named H. simus. In Hapalemur there is no free centrale to the carpus, and the same is the case with the six or seven species of Lepidolemur (Lepilemur), in which the first upper incisor is rddimentary or wanting, while the second may also be wanting in the adult. There are small lemurs, with small pre-maxillae, short snouts, tails shorter than the body, bladder-like mastoid processes, and the upper molars with an inconspicuous cingulum and the hind-cusps of the last two rudimentary; the fourth upper premolar being relatively broad. Mixocebus caniceps is an allied generic type (see LEMUR). The small Malagasy lemurs of the genera Chirogale, Microcebus and Opolemur differ from the preceding in the elongation of the calcaneum and navicular of the tarsus, on which grounds they have been affiliated to the African galagos. The difference in the structure of the tympanum in the two groups indicates, however, that the elongation of the tarsus has been independently developed in each group. These lemurs have short, rounded skulls, large eyes, long hind limbs and tail, large ears, the first upper incisor larger than the second, the last upper premolar much smaller than the first molar and furnished with only one outer cusp, and the mastoid not bladder-like. Some are less than a rat in size, and all are nocturnal. One of the largest, Microcebus furcifer, is reddish-grey, and distinguished by a dark median stripe on its back which divides on the top of the head into two branches, one of which passes forwards above each eye. The most interesting peculiarity of these lemurs is that certain species (Opolemur samati, Chirogale &c.) during the dry season coil themselves up in holes of trees, .and pass into a state of torpidity, like that of the hibernating animals in the winter of northern climates. Before this takes place an immense deposit of fat accumulates upon certain parts of the body, especially the basal portion of the tail. The smallest species, M. pusillus, lives among the slender branches on the tops of the highest trees, feeding on fruit and insects, and making nests like those of birds. In the sub-family Indrisinae the dentition of the adult consists of thirty teeth, usually expressed by the formula i. c. }, p. I, m. ; but possibly i. }, c. i, p. }, in. In the milk-dentition there are twenty-two teeth, the two additional teeth in the fore part of the lower jaw having no successors in the permanent series . Hind limbs greatly developed, but the tarsus normal, the great toe of large size, and very opposable; the other toes united at their base by a fold of skin, which extends as far as the end of the first phalange. The thumb is but slightly opposable; and all the fingers and toes are hairy. The length of the tail is variable Two pectoral teats. Caecum very large, and colon extremely long and spirally coiled. The brain is large and the thorax wide.The animals of this group are essentially arboreal, and feed exclusively on fruit, leaves, buds and flowers
Galagos and Lorises.The lemurs of Africa and the Indo-Malay countriescommonly miscalled slothsdiffer from the Lemuridae in that the tympanic enters into the formation of the auditory meatus, in consequence of which they are referred to a family by themselves, the Nycticebidae, which is in turn divided into two sub-families, Galaginae and Nycticebinae. The African galagos or Galaginae, which have the same dental formula as the Lemuridae, are distinguished by the elongation of the calcaneum and navicular of the tarsus. In the single genus Galago, with the sub-genera Otolemur and Hemigalago, the last upper premolar, which is nearly as large as the first molar, has two large external cusps. Vertebrae: C.7, D.13, L.6, S.3, Ca.2226. Tail long, and generally bushy. Ears large, rounded, naked and capable of being folded at the will of the animal. Teats four, two pectoral and two inguinal (see GALAGO). The lorises, Nycticebinae (Lorisinae), are distinguished as follows: Index- finger
(From A. Milne-Edwards.) (the existence of which has only recently been discovered by Messrs Annandale and Willey). In the slow lorises, forming the genus Nycticebus (fig. 22), the first upper incisor is larger than the second, which is often early deciduous. Inner margin of the orbits separated from each other by a narrow flat space. Nasal and ('mm Milne-Edwards and Grandidier.) to the ground, which is but seldom, they sit upright on their hind legs, and move from one clump of trees to another by a series of short jumps, holding their arms above them in the air. Among them are the largest members of the order. The genus Indris has the upper incisors sub-equal in size; upper canine larger than the first premolar, muzzle moderately long, ears exserted. Carpus without an os centrale. Tail rudimentary. Vertebrae: C.7, D.12, L.9, S.4, Ca.9. The indri (I. brevicaudatus, fig. 20), discovered by Sonnerat in 178o, is the largest of the group, and has long woolly hair, partly brown and partly white. In the sifakas, Propithecus, of which there appear to be three species, with numerous local races, the second upper incisor is much smaller than the first. Upper canine larger than the first premolar. Muzzle rather short. Ears short, concealed by the fur. An os centrale in the carpus. Tail :orig. vertebrae : C.7, D.12, L.8, S.3, Ca.28. In Avahis, represented only by A. laniger, the second upper incisor is larger than the first. Upper canine scarcely larger than the first premolar. Muzzle very short. Ears very small and hidden in the fur, which is very short and woolly. Carpus without os centrale. Tail long. Vertebrae: C.7, D.II, L.9, S.3, Ca.23 (see INORI and SIFAKA).. The last sub-family, Chiromyinae (formerly regarded as a family), is represented only by the aye-aye, Chiromys (or Daubentonia) madagascariensis, and has the following characteristics: Dentition of adult, i. }, c. p. in. }, total 18. Incisors (fig. 21) very large, compressed, curved, with persistent pulps and enamel only in front, as in rodents. Teeth of cheek-series with flat indistinctly tuberculated crowns. In the young, the first set of teeth more resemble those of normal lemurs, being i. , c. m. , all very small. Four premaxillary bones projecting but very slightly in front of the maxillae. Body and limbs stout. No tail. Vertebrae: C.7, D.r7, L.6, S.3, Cara. The single species N. tardigradus, with several races, in- habits eastern Bengal, the Malay countries, Sumatra, Borneo, Java, Siam and Cochin China. These lorises lead solitary lives in the recesses of large forests, chiefly in mountainous districts, where they sleep during the day in holes or fissures of large trees, rolled up into a ball, with the head between the hind legs. On the approach of evening they awake, and daring the night ramble among the branches of trees slowly, in search of food, which consists of leaves and fruit, small birds, insects and mice. When in quest of living prey they move noiselessly till quite close, and then suddenly seize it with one of their hands. The female produces but one young at a time. In the second genus, represented only by the slender loris (Loris gracilis) of southern India and Ceylon, the upper incisors are very small and equal. Orbits very large, and only separated in the middle line above by a thin vertical plate of bone. Nasals and premaxillae produced forwards considerably beyond the anterior limits of the maxillae, and supporting a pointed nose. Body and limbs slender. No external tail. Vertebrae: C.7, D.14, L.9, S.3, Ca.6. The slender loris is about the size of a squirrel, of a yellowish-brown colour, with large, prominent eyes, pointed nose, long thin body, long, angularly bent, slender limbs and no tail. Its habits are like those of the rest of the group. The Indian and Ceylon races are distinct (see LORIS). The African pottos, Perodicticus, differ by the reduction of the index-finger to a mere nailless tubercle, and apparently by the absence of abdominal teats. In the typical section of the genus there is a short tail, about a third of the length of the trunk. Two or three of the anterior dorsal vertebrae have very long slender spinous processes which in the living animal project beyond the general level of the skin forming distinct conical prominences, covered only by an exceedingly thin and naked integument. P. potto, the potto, is one of the oldest known members of the lemuroids having been described in 1705 by Bosman, who met with it in his voyage to Guinea. It was, however, lost sight of until 1835, when it was rediscovered in Sierra Leone. It is also found in the Gaboon and the Congo, and is strictly nocturnal and slower in its movements even than Nycticebus tardigradus, which otherwise it much resembles in its habits. A second species, P. batesi, in-habits the Congo district. A third species, the awantibo (P. calabarensis), rather smaller and more delicately made, with smaller hands and feet and rudimentary tail, constitutes the sub-genus Arctocebus. It is found at Old Calabar, and is very rare. Vertebrae: C.7, D.15, L.7, S.3, Ca.9. End of Article: CHIN If you wish, you can link directly to this article.
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