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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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