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ANT 3514 – Introduction to Biological Anthropology Primate Morphology Lab 4, Week of 1/26/04 This lab will give you tools to use in order to morphologically differentiate some types of primates from others. Below are a few things you will need to know in order to do this. You will see examples in lab. Pages 88-96 in your book will be useful for this lab. Dentition: Primates all have heterodont dentition. This means the teeth are not all the same. Primates possess different teeth used for different functions. These teeth are: Incisor: tooth designed for cutting Canine: tooth with pointed cusps for tearing and incising Premolars: teeth with broad occlusal (top) cusps for grinding and reducing food material as an aid to digestion Molars: same as premolars but with broader occlusal surfaces In primates, as in all toothed mammals, the dentition of each side of the jaw is a mirror of that on the other side. Therefore it is sufficient to describe only half of the dentition of the upper and lower jaw. However the number of teeth in the upper and lower jaws may differ, so each must be counted. To count dentition, start at the incisors and count around towards the back of the jaw. The teeth are counted like this: Incisors-canine-premolars-molars Incisors-canine-premolars-molars The upper jaw is on top and the lower jaw is on the bottom. Counting these teeth results in a dental formula. Primates can be identified by their unique dental formula. Primates have lost a premolar and an incisor in comparison with other mammals, so a primate dentition will look something like 2133 or 2123 2133 2123 Most other mammals have three incisors per side and four or five premolars. One special primate feature found in Strepsirhine primates is the dental comb. The dental comb is formed from the procumbent (tilted forward) incisors and canines on the lower jaw. Often, when there is a dental comb, the 1st premolar takes over the function and shape of a canine. It is then referred to as caniniform. Other features: It is also useful to look at the cusp pattern of molars. The cusps can have a bilophodont, nonbilophodont, or Y-5 pattern (see p. 96 in your book). Bilophodont molars have 4 cusps, arranged in two pairs and are characteristic of Catarrhine monkeys. Y-5 molars have 5 cusps arranged in a y pattern and are characteristic of humans and apes. You should also know the diastema, a space in the toothrow that accommodates one or more teeth in the opposite jaw when the mouth is closed. Crania: You can also differentiate amongst primates and between primates and other mammals by looking at their crania. Here are a few traits that will be useful for this purpose: Prognathic: having the lower face and jaws projecting in front of the upper parts of the face, having a protruding snout Orthognathic: The opposite of prognathic, having a flatter, less protruding snout Dental arcade: This is the shape of the upper toothrow along the palate. Monkeys and apes have a U-shaped or rectangular dental arcade. Humans have a parabolic dental arcade (p. 193 in your book). Supraorbital tori: Also known as the brow ridge. A continuous ridge of bone in the skull, curving over each eye and connected across the bridge of the nose. Sagittal crest: a ridge of bone running along the top of the skull which anchors the jaw muscles. Classification: Primate classification can either be grade or clade based. Grade based classifications are those such as Anthropoid vs. prosimian. They are not based on evolutionary relationships, but on arbitrarily defined differences and silimarities. Clade based classifications group organisms based on shared derived traits, with the aim of identifying groups of organisms descended from a common ancestor. This table shows some characteristics of primates in the clade based groups of Strepsirhine and Haplorhine. Strepsirhine Rhinarium present Frenulem present Two part mandible Postorbital bar Long muzzle Haplorhine No rhinarium No frenulem Fused mandible Complete bony eye socket Reduced muzzle The Haplorhine category can further be divided into these two infraorders: Platyrrhine (New World Monkeys) Widely spaced, round nostrils 12 premolars All have tails, some prehensile Non-bilophodont molars Catarrhine (Old World Monkeys) Closely spaced, downward pointing nostrils 8 premolars Not all have tails, none prehensile Bilophodont molars