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Characteristics of mammals
- -live birth
- -endothermic
- -fur or hair
- -mammary glands
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Synapsid
- first phase of mammalian evolution-pelycosaurs- sailbacked 'reptiles'
- -elongated neural spines - surface area allows blood to cool
- -therapsids
- -mammals
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therapsids- transitional characteristics
- mammal like 'reptiles'
- -developed heterodont teeth, tripartite division of jaw muscles
- -reduction in number of lower jaw bones- they evolved into ear bones
- -buttressing of skull
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the first true mammals
- tree dwelling - small bodied - insectivorous - nocturnal
- (marsupial like)
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Evolution in Cenozoic
- extinction of dinosaurs opened up niche space for diversification
- Planet began to cool, transition from greenhouse earth to icehouse earth
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Miocene-
- continued cooling trend with warmer periods - evolution of grasslands- first horses
- -they evolved larger teeth and body sizes because height gave advantages in tall grass
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Great American Interchange
- North and South America were connected by a land bridge in the Late Pliocene
- -sloths armadillos, anteaters, porcupines and opossums headed north
- -squirrels, rabbits, wolves, deer, horses and jaguars headed south
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Characteristics of Order Primates
- -grasping hands (opposable thumbs)
- -large relative brain sizes
- -eyes in the front of face
- - post-orbital bar (bone behind eye)
- -origin of primates- prosimian like animals from Late Cretaceous
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Anthropoids vs Prosimians
- Anthropoids-New and Old world monkeys, humans
- -even larger relative brain size
- -post-orbital closure
- -fused mandibular synthesis
- -nails
- Prosimians- lemurs, tarsiers - have open eye orbits, smaller, grooming claws
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Paleocene- beginning of Cenozoic
- Hominoid fossil sites in East Africa
- -rifting in NE Africa - develops MOR, rift basins that did not separate enough to fill with basalt, later filled with sediments, preserving hominoid fossils
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Hominid evolution
- Primitive Australopithicus
- Laetoli footprints show bipedality and possible family structure
- Intermediate Australopithicus
- robust- relatively smaller brains, large jawline and teeth
- gracile-smaller teeth and jaw, developing forehead
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Evolution of Genus Homo
- Homo Erectus- first hominoid outside Africa
- -developed tools
- Neandertal- found in Europe, East Asia
- Cro-Magnon
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Theories - Out of Africa Model vs. multiregional
- No connection between homoerectus and
- homosapiens sapiens
- All modern homo ss descend from homoerectus but evolved separately in each region
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Anthropoid superfamilies
- New World monkeys-South and Central America arboreal, no opposable thumbs
- Old World monkeys-native to Africa and Asia, baboons, colobus monkeys
- Hominoids- chimps, gorillas, humans and orangutans
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