Prosimians and Anthropoids Essay Example
Prosimians and Anthropoids Essay Example

Prosimians and Anthropoids Essay Example

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  • Pages: 3 (566 words)
  • Published: April 9, 2017
  • Type: Essay
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There are two main divisions of primates: Prosimians and Anthropoids. The lower division, Prosimians consists largely of the "lemurs," scattered through the Old World tropics from Africa through Madagascar to Southeast Asia, living in trees, mostly nocturnal in activity, eating fruit and insects, furry in coat, and about the size of a cat or smaller. They are appealing in appearance, and interesting animals, but they are hard to see in the wild because they sleep all day. They are more properly called prosimians, since this suborder of the primates is named Prosimii.

It includes lemurs, lorises, and other related "primitive" primates (Wallace, 2004). The higher primates are put in a second suborder named the Anthropoidea. This includes human beings, apes and monkeys. There are five families: three of monkeys, one of apes, and on

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e of men. Anthropoids have the same dental formula, or count, of the several kinds of teeth: 2-1-2-3 (two incisors, one canine, two premolars, and three molars, on either side of both jaws). They are diurnal, or day-living in habit. The back wall of the eye socket is well closed in, separating the socket from the depression in the temple region just behind (Wallace, 2004).

Prosimians are smaller than anthropoids and do not have fused skulls like the Anthropoids. The orbit (eye socket) is open in the prosimians whereas it is closed in anthropoids. Anthropoids have nails, while the prosimians have a grooming claw on the index finger of the hind foot. The rest of the digits have nails. The prosimians' teeth are also different; The incisors are almost horizontal in prosimians, and this is called the grooming comb because they use it to

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groom (UM, 2006). In the case of Anthropoids, the cerebral cortex extends backward more and more to cover the large brain.

The skull becomes rounder, and spine and mouth are alarmingly close to each other underneath. Anthropoids have fused mandibles while prosimians do not have them. Anthropoids have nails whereas prosimians have claws. Anthropoids fill more niches than Prosimians- places which are drier, colder, sparser etc. In the case of fossil identification, the teeth are the key. In prosimians, the small molar crowns have spiky cusps and deep recessions (are "tuberculosectorial”). In higher primates the crowns are broader, more level, with shallower, blunter cusps (UM, 2006).

The earliest known anthropoidlike fossils were the ones that the Austrian collector Richard Markgraf found at Fayum in Egypt. They were studied in 1911 by Schlosser, and belonged supposedly, to the early Oligocene. He named them Parapithecus and Propliopithecus. Propliopithecus, has the catarrhine tooth count and is instantly recognizable as a hominoid (division of anthropoid). His teeth are of simple pattern and include a fairly short and light canine and unspecialized bicuspids or premolars, not skewed in the direction either of later apes or of strongly "bicuspid" man.

Parapithecus was still simpler in nature. His incisors, canines and premolars all shaded into one another so gradually that it has never been decided which was which. For a long time the dental formula was accepted as being 2-1-2-3, making Parapithecus the perfect emerging hominoid. But Schlosser himself thought that the formula was one incisor and three premolars, so that at best he would be a dubious hominoid and perhaps not even a primate at all. Parapithecus eventually proved to have teeth more like

a New World monkey's than an ape's (Cirulis et al, 1967).

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