hominid-characteristics - Sahelanthropus tchadensis(Toumai...

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Sahelanthropus tchadensis (Toumai – one fossil) 7-6 mya Mix of primitive and derived features Ape-like ancestral features: Chimp-sized brain Features of back of skull like chimp Primitive teeth Hominid-like derived features: Flat face Foramen magnum oriented as it is in bipedal creatures (under the skull) No canine/PM diastema Dentition not like apes Massive brow ridge like much later hominids and like gorillas Australopithecus afarensis and A. africanus 4-2.2 mya Pelvis similar to humans’ Femur slanted inward from pelvis Abductor muscles helped create torque for bipedalism Skull flared out at bottom Foramen magnum indicates a biped Ape-sized brain Chimp-like inner ear Big toe in line with others (human-like) Ape-like shoulder blade, slender and curved fingers and toes, allowing it to locomote through trees Small bodies Teeth/jaws/skull intermediate between apes and later hominids, canines are medium sized, diastema (space between teeth and jaw) is modest, dental arcade has intermediate V shape Grew up quickly like apes Ape-sized brains (400-500 cc.) Pronounced sexual dimorphism (males weighed 30-50% more than females. In humans this is more like 10-20%), less dimorphism than chimps but more than humans Prognathic face A. habilis and A. rudolfensis 2.5-1.9 mya More rounded skull than earlier australopithecines (sides of skull slope upward more vertically)
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