Occipital condyles



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NUCHAL CREST

The part of the skull where the neck muscles attach. The nuchal crest is larger in apes than it is in humans because apes are mostly quadrupeds and have to keep their head from drooping.

OCCIPITAL CONDYLES

The parts of the skull that articulate with the vertical column. In humans, the condyles are relatively far forwards. In apes they are much further back.

SAGITTAL CREST

Ridge at the top of the skull to which the jaw muscles are attached. The sagittal crest is more prominent in primates (such as gorilla) which have a high fiber diet.

PROGNATHISM

This means “having a snout/muzzle”. Baboons are a clear example of a primate showing prognathism; whereas humans do not show prognathism

FORAMEN MAGNUM

The hole at the back of the skull through which the spinal cord enters the skull. The foramen magnum is more central in humans than it is in apes. This is because apes are quadrupeds and humans are bipedal.

BROW RIDGE

Heavy bone over the eyes. This is to protect the eyes.

The powerful chewing action of ape jaws sets up stresses in the skull and in the lower jaw. These are resisted by “brow-ridges” above the eye sockets, and also by a “simian shelf”, which strengthens the inside of the lower jaw.



Humans have no brow ridges


ZYGOMATIC ARCH

Gap through which large jaw muscles pass. Apes with a coarser plant diet had bigger jaw muscles.

DENTAL ARCADE (TOOTH ROW)

The tooth row (dental arcade) is parabolic (bow-shaped) in humans but is “U”-shaped in apes

DIASTEMA

In apes, the lower canine fits into a gap or diastema between the upper canine and the first premolar. Humans have no diastema

CANINE

Human canines are about equal in size in the two sexes, while those of the great apes are considerably larger in the male than in the female. The large canine are used predominantly for threat displays



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