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Tarsiers did not reinvent the eye of the nocturnal early primates, as tarsiers do not have a reflecting tapetum and they have retained the diurnal adaptation of a fovea Collins et al. Jon H. Kaas, in Progress in Brain Research Tarsiers represent an odd line of evolution in the primate radiation. Their overall small size and strange body confused early investigators, and tarsiers were grouped with lorises, galagos, and lemurs as prosimian primates, that is, below the monkey simian level. That classification has now been changed, and the molecular evidence places them as an early surviving branch of the anthropoid radiation Ross and Kay, What is unusual about the evolution of tarsiers is that early anthropoids were diurnal and specialized for daytime vision, and the tarsier line started off as diurnal, having lost its specializations for nocturnal vision, but then returned to nocturnal life by re-specializing for dim light.

This largely consisted of evolving huge eyes relative to the head. Consistent with their reclassification, the dorsal lateral geniculate lamination pattern of tarsiers is clearly of the anthropoid type, rather than of the strepsirrhine type Wong et al. As an extreme visual predator of insects and other small prey, tarsiers depend on a large V1 for the detailed representation that is needed for this function.

As tarsiers are small, and have small brains, this dependence on a large V1 may have cost them in of cortical tarser. They have a V2 and MT and likely other visual areas, but tarser posterior parietal cortex and little prefrontal cortex. Henry R. Hermann Ph. Tarsiersprosimians from Southeast Asia, with four extant species, live in tropical rain forests Clutton-Brock and Wilson, Fig. While tarsiers are included in the prosimian group, some researchers view them as a link between prosimians and simians. Clutton-Brock uses the western tarsier as an example of the group.

They are nocturnal and adept at climbing and grasping tree branches. It has a small, tarser body, with slender fingers, padded toes, and sharp claws. It feeds chiefly on insects and usually sleeps on branches, rarely using nests for shelter. Figure 5. A Tarsier, a nocturnal prosimian that some biologists feel is a link between prosimians and simians. B Gibbon, a lesser ape, showing its long forelimbs that are used in brachiation. C—F Greater apes. C Orangutan. D Gorilla. E Chimpanzee, showing opposable big toe.

F Bonobo. John G. Tarser tarsiers of Southeast Asia Table 4. They show a mixture of prosimian and anthropoid features. However, their similarities to other prosimians are primitive features: an unfused mandibular symphysis, molar teeth with high cusps, grooming claws on their second and third toes, multiple nipples, and a bicornuate uterus. Their similarities to anthropoid primates seem to be derived specializations indicative of a phyletic relationship. In addition, tarsiers have many distinctive features all their own Fig.

TABLE 4. The skull, dentition, and tarser of a tarsier, showing some of the distinctive features of the genus.

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Tarsiers differ from other nocturnal primates, and resemble all diurnal primates in having a retinal fovea and lacking the reflective tapetum found in all lemurs and lorises, as well as many other groups of mammals. Their large eyes are protected by a bony socket that is partly closed posteriorly, similar to that of higher primates. The nose of tarsiers resembles that of higher primates as well, both externally in the lack of an attached upper lip with a median fold, and internally in the greatly reduced turbinates and in the absence of a sphenoid recess.

In tarsiers, as in higher primates, the major blood supply to the brain comes through the promontory branch of the internal carotid Fig. The tympanic ring lies external to the auditory bulla and extends laterally to form a bony tube, the external auditory meatus.

The tarsier dental formula, 2. The postcranial skeleton of tarsiers is striking in many of its proportions. The hands and feet of these tiny animals are relatively enormous, reflecting both their clinging abilities and their predatory habits Fig. They have extremely long legs and many more specific adaptations for leaping, including a fused tibia and fibula and the very long ankle tarser responsible for their name. A pair of tarsiers Drawing by Stephen Nash.

In their reproductive physiology, tarsiers show several similarities to higher primates, as noted above. They have a hemochorial placenta like that of monkeys, apes, and humans, rather than the epitheliochorial type found in lemurs, and they produce relatively large offspring. Female tarsiers undergo monthly sexual cycles, with swellings reminiscent of some Old World monkeys. Living tarsiers are currently divided into three genera and 11 species Table 4. The genus Tarsius, with nine species, is restricted to Sulawesi and nearby small islands.

The other two tarsier genera are, at present, monotypic. Carlito syrichta is from the Philippines, and Cephalopachus bancanus is from Borneo, Sumatra, and nearby small islands. The allopatric tarsier genera differ in numerous morphological features, including body size, tarserlimb proportions, orbit size, of nipples, and patterns of vocalization and sociality. The distribution of the three genera of tarsiers in southeast Asia. Drawing by Stephen Nash. Tarsiers seem to be common tarser many types of forest, but they are particularly abundant in secondary forests and scrub.

They are totally nocturnal and tarser their days sleeping in the grass or on vines in trees. Tarsiers often travel and feed very near the ground. In Sulawesi, tarser activities, such as calling and resting, take place higher in the canopy. All tarsiers move mainly by rapid leaps of up to 3 m. The Bornean tarsier seems to be most committed to vertical clinging and leaping, but this may reflect differences in data collection Dagosto et al.

Tarsius pumilus, the pygmy tarsieris unusual in having keeled nails for clinging to moss-covered trees.

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All tarsiers are totally faunivorous: they eat insects, arachnids, and small vertebrates such as snakes and lizards. There is evidence from both naturalistic and captive studies of considerable differences in social behavior among and within species Gursky, Philippine and Bornean tarsiers have been reported to live in a noyau system, with solitary individuals living in overlapping ranges. Philippine tarser always sleep alone. Sulawesi tarsiers, on the other hand, live in families or perhaps small polygynous groups.

These families sleep together, give complex territorial duet calls early every evening, and then forage together all night. Males and females actually chase other tarsiers out of their territories. All tarsiers have a remarkably long, six-month gestation period and one of the lowest rates of fetal growth among mammals Roberts, During that time, they seem to develop adult prey-catching patterns.

Females are largely responsible for care of the infant and usually park the infant while foraging Gursky, In contrast to many monogamous species, there is no indication of male infant care in tarsiers. Valverde Celia R. TarsiersNew World and Old World monkeys have a flask-shaped simple stomach. The rhesus stomach is positioned lower and more horizontally than in humans, due to the shape and size of their liver Hartman et al.

The stomach structure of colobines Colobus and Presbytis differs from any other primate and resembles that found in ungulates, with a pseudoruminant anterior fermentation area in a large multichambered stomach.

The stomach is large and tarser, though not truly compartmentalized. The sacculations are produced by reduced longitudinal muscle bands. The size of the stomach and colon tend to be proportionally larger in folivorous nonhuman primates. These animals also tend to be larger in stature to accommodate for their sizeable gastrointestinal tract. The colobine stomach may constitute up to a quarter of the adult body weight and up to half for a semi-weaned infant.

The Pongidae stomach is indistinguishable from human beings. For most of the past decade, the enlarging fossil record of early anthropoids and increasing s of detailed phylogenetic analyses appeared to have settled earlier debates over the broader question of the phyletic origins of anthropoids, or, tarser specifically, which group of prosimians gave rise to higher primates Fleagle and Kay, ; Kay et al. There is widespread agreement among primatologists and mammalogists that, among living primates, anthropoids seem to be more closely related to the living tarsiers than to living lemurs and lorises.

When we consider fossil prosimians, however, the tarser phyletic relationships between anthropoids and tarsiers and various groups of living and fossil prosimians are less settled. Thus, there are three distinct views regarding which extant or fossil clade is the sister group of Anthropoidea Fig. Hypotheses of anthropoid origins. As noted in Chapter 4tarsiers share with anthropoids many similarities in reproductive anatomy, eye structure, and cranial anatomy, as well as biochemical similarities not found in other living primates.

Moreover, two features that unite tarsiers and anthropoids, postorbital closure and the development of an anterior accessory chamber of the middle ear, are unique among primates and even among mammals, rather than being similar features that appear to have evolved in numerous groups.

Although the cranial similarities linking tarsiers with anthropoids have been questioned Simons and Rasmussen ; Beard and MacPhee,there seems little reason to do so on morphological grounds Cartmill, ; Ross, Among all known fossil and extant prosimians, only tarsiers share any evidence of either of these traits with anthropoids.

The extensive phylogenetic analyses of anthropoid origins by Kay, Ross and Williams e. However, although the dentition of early anthropoid taxa such as Eosimias could be interpreted as supporting tarsier—anthropoid affinities, the absence of common tarsier—anthropoid features in the ear region attributed Eosimias suggests that these tarser may have evolved in parallel Kay et al.

Many authorities have argued that the sister taxon of anthropoids is not the genus Tarsius specifically, but some omomyoid, or tarser broadly the clade including omomyoids and Tarsius. In their view, tarsiers are a branch within omomyoids, and thus both tarsiers and anthropoids are descended from some common tarsiiform or omomyoid ancestry e. In this view, the features uniting tarsiers and anthropoids are either primitive features common to most omomyoids or, in the case of postorbital closure, convergent and not really homologous.

As with the tarsier—anthropoid hypothesis, the omomyoid origins hypothesis accords with notions of a haplorhine—strepsirrhine dichotomy among primates, tarser molecular studies linking tarsiers with anthropoids, and with studies that argue for the origin of tarsiers from particular omomyid taxa.

The biggest weakness of this scenario is that the cranial features that most clearly link tarsiers with anthropoids postorbital closure and anterior accessory chamber of the middle ear are not present in any omomyoids, including the taxa that share various other cranial features with tarsierssuch as Shoshonius There are a few derived features probably an apical interorbital septum and reduced nasal region, and a few postcranial characters that link some omomyoids with anthropoids and tarsiersbut if tarsiers are indeed derived from any of the taxa most frequently proposed Tetonius, Shoshonius, and Necrolemurthen the unique tarsier—anthropoid cranial features have evolved independently in tarsiers and anthropoids.

Tarser present the relationships among omomyoids, tarsiers, and anthropoids tarser unresolved.

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Of all primates only Tarsius lives exclusively on animal protein; insects, larvae, and lizards and various tarser small vertebrates constitute the tarsier diet. The two lorisid genera Arctocebus and Loris are, like tarsiers, said to be diet specialists that consume only animal protein Nekaris and Rasmussen, The lemurid Lepilemur appears to be the smallest prosimian that is purely vegetarian and has a diet that is highly fibrous.

The indriid genera Indri and Propithecus are highly specialized herbivores, and their bodies are consequently rather pear-shaped, showing the enlarged gut of a bulk eater Campbell et al. Among monkeys, both the South American howler monkey and the colobines of the Old World are highly specialized leaf eaters showing, however, very different degrees of specialization in this dietary adaptation, as discussed later Tarser, ; Cork, The highland gelada baboons— Theropithecus gelada —are specialized seed and root eaters Jolly, Among the great apes, gorilla is said to be a herbivore, the orangutan predominantly a frugivore, and the chimpanzee an omnivore.

The migratory habits of most primates are closely related to the availability of food. Chimpanzees, for example, go every day to areas where certain fruit are ripe and abundant, returning day by day until the supply is exhausted, and they have to find another area in which to forage. Both baboons and chimpanzees eat a variety of small mammals and antelope meat. Especially chimpanzees actively hunt in groups Jolly, and thus assertively include meat into their diet.

Predatory behavior involving two species of South American monkeys has also been reported. Among New World monkeys the tufted capuchin Cebus apella is known to be exceptionally faunivorous, eating crabs and oysters and capturing small mammals. An adult male tufted capuchin monkey is reported to have tarser and eaten an infant titi monkey Callicebus moloch Sampaio and Ferrari, ; Simmen, Members of the subfamily Cercopithecinae have food pouches in their cheeks.

These enlargements of the membrane of the oral cavity outside the teeth can be enormously stretched. Such tarser are used as storage bags for food if it is abundant, or can be stuffed full in a hurry if the situation requires a hasty retreat, and then the hidden food can be retrieved and eaten in peace in a hiding place. These cheek pouches, when fully stuffed, can result in a different—even grotesque—appearance of a primate. Cheek pouches can extend far beyond the facial area, even bulging out and down into the neck. If the pouch is overstuffed, the primates often need to push the food items back out with the help of their hands because the cheek musculature is weakened by stretching.

As already mentioned, the South American howler monkeys and the Old World langurs Colobinae are highly specialized leaf eaters Cork, This specialization, however, is much more elaborate in colobines than in howler monkeys Chivers, ; Lambert, This is not the case for howler monkeys, which have comparatively tarser stomachs and the same basic stomach tarser as all other primates that ingest plant foods such as fruit, buds, and leaves. Also, howler monkeys ingest comparatively more fruit than do colobines, even though leaves dominate the diet of several howler monkey species Milton et al.


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Philippine tarsier