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Paleontology 1-

Vertebrate Lab

Graptolites

Fish

Conodonts

Amphibians

Reptiles

Birds

Mammals

Vertebrate Evolution

Chordates – Animals with a notocord, not necessarily a backbone.

Vertebrates are a subphylum of Chordates

Earliest records of Chordates are without vertebrae, soft-bodied.

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–a notochord, a dorsal hollow nerve cord, and gill slits

Amphioxus

Oldest Known Chordate

Yunnanozoon lividum 525 million year old rocks of China

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Phylum Chordata

Graptolites

Subphylum Vertebrata

Conodonts

Fish

Sharks

Bony Fish

Tetrapods

Amphibians

Reptiles

Amniote egg

Birds

Mammals

Horse teeth

Marine

mammal

vertebrae

Graptolites

Nemagraptus gracilis.

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Fish

Ostracoderms –

–earliest (Cambrian and Ordovician)

– jawless

– shallow marine

–Probably bottom feeders

Ostracoderms

Cambrian to Devonian

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Fish evolve jaws

Joints in forward gill arches

Mouth could open wider –Pumped more oxygen past gills

–Allowed eating larger prey

Acanthodians – 1st jawed fish –Spiny, scaly, teeth, reduced body armor

–Most abundant in the Devonian, extinct in Permian

Fish with jaws: 1st Acanthodians

Various primitive acanthodians from Early Devonian England and

Scotland, Mesacanthus pusillus, Parexus falcatus, Ishnacanthus

gracilis

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Age of Fishes = Devonian

Placoderms

– Late Silurian to Permian

–Plate-skinned fish – heavy armor

–Freshwater and ocean

–Bottom dwellers (small) and Large predators

Dunkleosteus More than 12m in length

Phyllolepis

Coccosteus (top, Middle Devonian), Campbellodus (left, Late Devonian),

and Bothriolepis (bottom right. Late Devonian) ©

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Age of Fishes = Devonian

Cartilaginous fish – Chrondrichthyes

–Sharks, rays and skates

–Early Devonian to recent

White shark

Ray

Skate

Age of Fishes = Devonian

Bony Fish – Osteichthyes – Ray-finned fish: with thin bones radiating in fins

Devonian to Recent

Most common fish today; Mesozoic and Cenozoic

– Lobe-finned fish: with thick bones and muscles for fins Silurian to Recent

Many extinct in Permian

Coelacanth- thought to be extinct in Cretaceous, found in modern seas = Latimeria

Lungfish has modified swim bladder that allows it to breath air

Crossopterigians probably evolved into amphibians

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Transition to Amphibians

Group of Crossopterigians called rhipidistians appear to be ancestors of amphibians

Structural similarities are striking

Earlier and earlier finds are causing some rethinking of timing (Acanthostega)

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Crossopterigian Amphibian

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Vertebrates Invade Land

Several transitional species

–Acanthostega – many features of amphibians but not truly land dwelling; shallow fresh water

–Panderichthys – transitional, shallow water

–Tiktaalik roseae – fish and tetrapod features

Oldest known amphibian, Ichthyostega, Late Devonian

Acanthostega

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Panderichthys

Ichthyostega – oldest amphibian

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Carboniferous Landscape

Labyrinthodont – Late Paleozoic

Proterogyrinus

Labyrinthodont

tooth cross-section

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Eryops Large labyrinthodont amphibian

Fate of the Amphibians

Many became extinct at Permian/Triassic extinction event (66%)

Few survived the Cretaceous/Tertiary event and those are small

Frogs, salamanders etc.

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Reptiles conquer the land

Amphibians must have water in which to lay gelatinous eggs.

Reptiles have Amniotic Eggs that have shells and don’t dry out in air.

Reptiles therefore could venture farther onto the land

Amniote Egg

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Westlothiana – Oldest reptile?

Late Mississippian of Scotland

Hylonomus lyelli

30 cm long. Joggins Cliffs, Nova Scotia

Found in tree stumps

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Pelycosaurs

Fin-backed reptiles Evolved in Pennsylvanian; dominant by

Permian Herbivores and Carnivores Sail back used for?

– Sexual display – Protection – Scary display – Thermoregulatory device

Capture sun’s heat Turn to wind for cooling

Reptiles conquer the land

Amphibians must have water in which to lay gelatinous eggs.

Reptiles have Amniotic Eggs that have shells and don’t dry out in air.

Reptiles therefore could venture farther onto the land

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Amniote Egg

Westlothiana – Oldest reptile?

Late Mississippian of Scotland

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Hylonomus lyelli

30 cm long. Joggins Cliffs, Nova Scotia

Found in tree stumps

Pelycosaurs

Fin-backed reptiles Evolved in Pennsylvanian; dominant by

Permian Herbivores and Carnivores Sail back used for?

– Sexual display – Protection – Scary display – Thermoregulatory device

Capture sun’s heat Turn to wind for cooling

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Fate of the Reptiles

66% of reptiles and amphibians became extinct in the Permian/Triassic mass extinction event

Reptiles radiated in the Mesozoic to become dominant animal life form

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Reptiles

Stem reptiles are the protothyrids of the Mississippian

Pelycosaurs were dominant in the Pennsylvanian and Permian (sail-backs)

Archosaurs include crocodiles, pterosaurs, dinosaurs, and birds

Dinosaurs

Archosaurs – ancestors of the dinosaurs

–Small (<1m long)

– Long legged

–bipedal

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Dinosaurs and Relatives

Two Types of Dinosaurs

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Hadrosaur “Duck –billed”

dinosaur

Miasaura nest and chick

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Ceratopsids

Triceratops

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Stegosaurus skull and reconstruction

Ankylosaurus reconstruction

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Brachiosaurus

Diplodocus skull

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Theropod teeth, on the other hand, retain the primitive

archosaurian characteristic of being recurved, serrated,

laterally -compressed, and knife-like. There is some

variation in tooth structure among extinct theropods, but

most are fairly similar and obviously related to a

carnivorous diet.

Typical Theropod Dinosaur

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Theropod teeth, on the other hand, retain the primitive

archosaurian characteristic of being recurved, serrated,

laterally -compressed, and knife-like. There is some

variation in tooth structure among extinct theropods, but

most are fairly similar and obviously related to a

carnivorous diet.

Typical Theropod Dinosaur

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Sordes sp. Note membrane connecting legs, note also tail

Engraving of first Pterosaur found in Late Jurassic Solenhofen Limestone, 1784. 29 species have been found since in this site alone.

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Grippia longirostrus from Triassic of Spitzbergen

Shonisaurus popularis From the Jurassic of Nevada

Dolichorhynchops, a short necked, long jawed plesiosaur, National Museum of Natural History,

Washington D. C.

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Restoration of Plesiosaurus dolichodeirius

Grippia longirostrus from Triassic of Spitzbergen

Shonisaurus popularis From the Jurassic of Nevada

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Dolichorhynchops, a short necked, long jawed plesiosaur, National Museum of Natural History,

Washington D. C.

Restoration of Plesiosaurus dolichodeirius

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Evolution of Birds

Jurassic Archaeopterix

–Reptile teeth

–Reptile skeletal features

–Feathers

–Fused clavicle (wishbone)

–Hollow bones

–True ancestor or separate extinct line?

Archaeopterix

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Paleogene Giant, Flightless Bird

Evolution of Mammals

Cynodonts are closest to mammals in skeletal details

–Based on details of middle ear, lower jaw, and teeth

–Mammals have teeth differentiated for different purposes

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Cynodont

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Oldest known

marsupial

Mammal

Earliest known

Placental Mammal

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Other Mammals

Momotremes – Descended from Triconodonts

–Egg laying

–Today = Platypus and Spiny Anteater

Triconodont

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The Age of Mammals

Types of Mammals

–Monotremes –egg laying Mammals

–Marsupials – Carry embryo in pouch

–Placetal mammals – Have Placenta, give birth to live young

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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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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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Pleistocene Extinctions

What caused the extinctions?

Why in Australia and the Americas?

Why mainly the large mammals?

Hypotheses

–Climate change

–Human decimation

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

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

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

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Primate and Human Evolution

Hominids

–Bipedal

–Upright posture

– Large, reorganized brain

–Reduced canines- omnivorous teeth

– Increased manual dexterity

–Use of sophistocated tools (modified)

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

–