Exam_3_Study_Guide - Exam3StudyGuide 22:06:00...

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Exam 3 Study Guide 16/01/2009 22:06:00 Early Hominid Evolution  Provide dates and describe the fossils for the following members of the hominoid- hominid phase:  Sahelanthropus o between 7 and 6 myo o primitive traits small brain long, flat nuchal plane with a large external occipital crest-  similar known fossils of hominoid genera canine similar to chimps dental arch is small, narrow, U shaped enamel thickness of post canine teeth is between hominoids and  Australopithecus o advanced hominid features face is more orthognathic (vertical) than in apes orbits separated by a wide interorbital pillar thick brow ridge premolars/molars smaller than living hominoid genera basicranium small occipital condyles- associated w/ large foramen  magnum Orrorin o 6 myo o primitive upper central incisors- large and robust like apes
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upper canines large- reained narrow and shallow anterior groove- like  apes premolars smalle and apelike. . molars small and apelike o humerus- straight lateral crest- brachial muscle was attached o digits curved like arboreal primates o advanced derived femur- large and thick head of femur- trochanter- well developed fossa trochanterica femur has deep groves where thigh muscles attached- bipedalism Ardipithecus  o 5.8 to 4.4 myo o enamel thickness comparable to hominids third molar has 4 distinct cusps- apes o phalanx of upper limbs similar to early hominids ulnar shift more curved o could have been retained some arboreal adaptations/ been adapted to  bipedalism What is the key trait which distinguishes hominids from other hominoids (great apes)?  bipedal locomotion Australopithecus  Describe how the following traits differ between robust and gracile species.  What do  these suggest about dietary differences? … Gracile- craniofacial features not as  pronounced o Sagittal crest (thin plate of bone extending down the center of the brain case)  and zygomatic arch (cheek bones) Robust-  prominent sagittal crest… flaring zygomatic arches o Molar size and enamel thickness 
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Robust- large premolars and molars Gracile- small canine teeth
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Exam_3_Study_Guide - Exam3StudyGuide 22:06:00...

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