Cenozoic Life History - CCSF€¦ · 5/19/2011 1 Cenozoic Life History Marine Invertebrates and...
Transcript of Cenozoic Life History - CCSF€¦ · 5/19/2011 1 Cenozoic Life History Marine Invertebrates and...
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Cenozoic Life History
Marine Invertebrates and Phytoplankton
Terminal Mesozoic extinction took out Ammonites, Rudists, most planktic forams, much of the phytoplankton
Survivors flourished and diversified
– Foraminifera – large and small
– Diatoms –great deposits of diatomite in Miocene
– Corals form reefs in warm waters
– Bryozoans (smaller and more ornate) thrive
– Bivalves and Gastropods rule and become increasingly modern and familiar
– Echinoids become more infaunal (Sand dollars)
Cenozoic is quite provincial due to changing ocean currents and latitudinal temperature gradient
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Cenozoic Vegetation and Climate
Angiosperms came to rule, but gymnosperms and
seedless vascular plants still numerous
Leaves with entire smooth edges and drip points
indicate high rainfall, warm conditions
– Paleocene of Colorado
– Oligocene Florissant Beds of Colorado
Leaves with incised margins indicate cool, dry
climates (Wolfe)
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Paleocene-Eocene Thermal Maximum
Abrupt warming trend 55 mya
Ocean circulation disrupted, deep warm
water, release of methane, greenhouse
effect
Subtropical plant fossils in western North
America indicate warmest period of Cenozoic
in Paleocene and Eocene – Pan-tropical
conditions
Plants and Climate
Oligocene drop in temperature
General decrease in precipitation in
midcontinent of North America
– Grasslands with scattered trees (Savannah)
– Grasslands (Steppe)
– Seen in the teeth of mammals
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Cenozoic Birds
Paleogene may be called the Age of Birds – 1st members of many modern groups evolved
– Large predatory birds took over that niche before mammals
Miocene saw songbird explosion
Pleistocene large, flightless birds e.g. Moas, elephant birds
Flying birds rule the sky
The Age of Mammals
140 my were small and not very diverse
(Mesozoic)
Exploited the niches left by the dinosaurs
and other reptiles – land, sea and air
Continued diversification at surprising speed
throughout the Cenozoic
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The Age of Mammals
Types of Mammals
– Monotremes –egg laying Mammals
– Marsupials – Carry embryo in pouch
– Placental mammals – Have Placenta, give birth to
live young
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Paleocene Mammals
Some holdovers from Mesozoic, soon extinct
Archaic Mammals: insectovores, marsupials and multituberculates
New Mammals: rodents, rabbits, primates carnivores, ancestors of hoofed animals
Most mammals small; some orders became extinct
No match for giant birds
Eocene and Oligocene Mammals
Larger
Ancestors of many living orders
Very large mammals included uintatheres
and titanotheres
Oligocene drying produced diversification to
more modern fauna
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Small mammals
Most mammals are small
Insectovores (including shrews, moles,
hedgehogs)
Rodents (largest are beavers and capybaras)
Rabbits
Bats – modification of the hand to wing and
flight
Carnivorous Mammals
Predators and meat eaters (some omnivorous)
Most have pointed, specialized teeth – carnassials
Uncommon as fossils because uncommon in life – represent 5% of warm-blooded population
Many are solitary animals (not all)
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Diversification of Carnivores
Began with creodonts and miacids; creodonts extinct in Miocene
Similarity of dogs and hyenas = convergent evolution
Saber-tooth cats repeatedly evolved through the Cenozoic
Aquatic carnivores related to bears
See p 384 fig 18.13
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Ungulates or Hoofed Mammals
Artiodactyla
– Even number of toes
– Distinctive teeth
– Cattle, goats, sheep, swine, antelope, deer, Hippopotomi
Perissodactyla
– Odd number of toes
– Distinctive teeth
– Horses, rhinoceroses, tapirs, many fossil examples
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Elephants
Proboscidea –long snout
Widespread in Cenozoic; now only two species – Indian and African
Eocene Moeritherium probably semi-aquatic
Oligocene trend toward large size, trunk and tusks
Mastodons and Mammoths of Pliocene & Pleistocene – all of Northern Hemisphere
Giant Aquatic Mammals – Whales
Cetacea – includes whales, dolphins,
porpoises
Had land dwelling ancestors: artiodactyls?
Carnivores?
Recent finds are bridging gaps in the record
and show the transition from land to marine
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Miocene Mammals
Relatives of elephants, chalcothere, oreodonts, small camels, bear dogs,
Saber-toothed cat, cranes
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Pliocene Mammals
Mastodon, rhinoceros,
Cranioceras rodent, rabbit,
Pronghorn, Sythetoceras,
Pliohippus
Pleistocene Faunas
Trend toward large body size – all over the
world
– Adaptation to cooler conditions of ice ages?
– Large animals retain body heat longer
Excellent assemblages in Florida and Los
Angeles (La Brea pits)
– La Brea with inordinate number of carnivores.
Why?
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Large Pleistocene Faunas
Sloths and armored glyptodonts of Florida
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Rancho La Brea, LA county Natural History Museum
Pleistocene Extinctions
What caused the extinctions?
Why in Australia and the Americas?
Why mainly the large mammals?
Hypotheses
– Climate change
– Human decimation
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Intercontinental Migrations
Land bridges common in Northern
Hemisphere
South American-North American connection
in the Pliocene
– The Great interchange
– 50% of S. American are placental; 20% of N.
American came from S. America
Australia still the home of the marsupials
Primate and Human Evolution
Human ancestors may go back as much as 7 million years
Not a straight line – branches that became extinct
What are Primates? – Characteristics related to being arboreal
Skeleton, mode of locomotion
Increased brain size
Smaller, fewer, less specialized teeth
Stereoscopic vision
Opposable thumb
– Prosimians and Anthropoids
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Primate and Human Evolution
Prosimians – lower primates – Lemurs, lorises, tarsiers, tree shrews
– Record from Paleocene – first primates
– Small, 5 digits, clawed hands and feet, forwardly directed eyes with night vision – nocturnal
– Eocene – abundant, retreated when cooler climate of the rest of Cenozoic
– Moved southward to Asia, Africa, Southeast Asia, Madagascar
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Primate and Human Evolution
Anthropoids – Evolved from prosimian lineage in Late Eocene
– Old World Monkeys-Cercopithecoidea
Non-prehensile tail
Grasping hands
Macaque, baboon, proboscis monkey
– New World Monkeys- Ceboidea
Evolved from Old World Monkeys in Oligocene and migrated to S. America
Prehensile tail
Howler, spider, squirrel monkeys
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Primate and Human Evolution
Hominoids – Great Apes (Pongidae)
Chimpanzees, orangutans, gorillas
– Lesser Apes (Hylobatidae) Gibbons, siamangs
– Hominids (Hominidae) Humans and their extinct ancestors
– Evolved from Old World Monkeys before Miocene
– Ancstral group included Aegyptopithecus
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Primate and Human Evolution
Homonoids diversified and migrated as
climate became cooler in Cenozoic
– Dryopithecines evolved in Africa in Miocene
E. g. Proconsul
– Sivapithecids
Eg Gigantopithecus
A separate branch from humans
Primate and Human Evolution
Hominids
– Bipedal
– Upright posture
– Large, reorganized brain
– Reduced canines- omnivorous teeth
– Increased manual dexterity
– Use of sophistocated tools (modified)
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Miocene Proconsul
Primate and Human Evolution
Hominids – Oldest remains Sahelanthropus tchadensis nearly 7 million years
old
– Human-chimpanzee line separated from gorillas about 8 million years ago
– Other older remains show transitional features
Australopithecines
Homo habilis
Homo erectus
Neanderthals
Cro-Magnons
Modern Humans –
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Sahelanthropus tchadensis 7 million years old, oldest homonid
“Lucy”
Autralopithecus afarensis
3.5mya
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