Fleagle J. 1088 Notes for Week 1

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University of Toronto Mississauga
Sherry Fukuzawa

NotesFromReadingFLEAGLEJ1088THEPRIMATEBODYPP1135Primate AnatomyCompared to most other mammals we primates have retained relatively primitive bodiesNo primates have departed so dramatically from the common mammalian body planThe anatomical features that distinguish the bones and teeth of primates from those of many other mammals are the result of subtle changes in the shape and proportion of homologous elements rather than major rearrangements losses or additions of body parts We generally find the same bones and teeth in all species of primates with only minor differences reflecting different diets or locomotor habits SizeAdult living primates range in size from mouse lemurs and pygmy marmosets with a mass less than 100 g to male gorillas with a body mass of over 200 kgFossil record provides evidence of a few extinct primates from early in the age of mammals that were much smaller and at least one Gigantopithecus blacki from the Pleistocene of China that was much larger probably over 300 kgAs a group primates are rather mediumsize mammalsCranial AnatomyBones of the Skull The adult primate skull consists of many different bones that together form a hollow bony shell that houses the brain and special sense organs and also provides a base for the teeth and chewing musclesOnly the lower jaw or mandible and the three bones of the middle ear are separate movable elements the others are fused into a single unit the craniumThis unit can roughly be divided into two regions a more posterior braincase or neurocranium and a more anterior facial region or splanchnocraniumThe braincase serves as a protective bony case for the brain a housing for the auditory region and an area of muscle attachment for the larger chewing muscles and muscle move head on neckThe frontal parietal and temporal bones make up the top and sides of the braincaseThe posterior and inferior surfaces of the braincase are formed by a single bone the occipital which also has a number of distinct parts Sphenoid forms the anterior surface of the braincase and joins it with the facial regionFacial region is formed by the maxillary and premaxilary bones which contain the upper teeth the zygomatc bone which forms the lateral wall of the orbit or eye socket the nasal bones which form the bridge of the nose and numerous small bones that make up the orbit The lower jaw or mandible contains the lower teeth In mammals and most prosimian primates the two halves of the mandible are loosely connected anteriorly in such a way that they can move somewhat independently of one anothermandibular symphysis In higher primates including humans the two sides of the lower jaw are fused to form a single bony unit Much diversity in primate skull shape reflects the need for single bony structure to serve numerous often conflicting functionsoEx Although size of the orbits is most directly related to the size of the eyeball and to whether a species is active during the day or night it influences the shape and position of the nasal cavity and the space available for chewing muscles Teeth and Chewing Hyoid bone is a small bone suspended in the throat beneath the mandible
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