Additions to the Late Pleistocene Vertebrate Paleontology of the
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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
–