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Vertebrates

Vertebrates. Many groups known only from fossils. Sharks. Bony fish. Lampreys. Coelacanth. Land vertebrates. Hagfish. Cladogram of vertebrates, stressing early forms from UC Berkeley Museum of Paleontology. Vertebrate characters. Cranium – brain case

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Vertebrates

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  1. Vertebrates Many groups known only from fossils Sharks Bony fish Lampreys Coelacanth Land vertebrates Hagfish Cladogram of vertebrates, stressing early forms from UC Berkeley Museum of Paleontology

  2. Vertebrate characters • Cranium – brain case • Vertebrae (spinal protection of cartilage or bone) – almost all • agility • speed • No larval stages • Evolved during Cambrian (early Paleozoic) Myllokunmingia fossil from SE China, -530 my

  3. Trends in vertebrate evolution • improvements in vertebral column – cartilage, bone • gill slit supports – jaws, other head bones • appendages – fins, legs, wings • respiration – gills & lungs • circulation – heart • reproduction – eggs, shells, “live” young • existing (& some extinct) classes trace some of the most important advances along the vertebrate evolutionary path – next slides follow these

  4. No Jaws • Hagfish • cartilage • partial cranium • slime a defense mechanism • Lampreys • cartilage • full cranium • fish parasites & free living hagfish tie themselves into knots to clean themselves

  5. evolved from gill arches later bore teeth mid Paleozoic (Silurian) origin Jaws recent Swedish shark Carcharodon megalodon Miocene (Cenozoic) shark Dunkleosteus Devonian (mid Paleozoic) Placoderm

  6. Jaws II

  7. also: articulated cranium & spine appendages (fins) - some paired modern day Cartilaginous Fish sharks, rays, etc. no swim bladder – must swim to “levitate” 1 m Jaws III Manta Ray

  8. Bone • Bony fish = ray-finned fish • also bony scales • most numerous & diverse vertebrate • lungfish have “lungs” • gut pockets • modified circulation

  9. Legs • Amphibians • the mosses of the animal world • limbs supported by bones • support • movement • articulated to “girdles” • connections to spines • hips and shoulder • but amphibians tied to water: • at least eggs (shell-less) • & larval stages young Rough-skinned Newt

  10. Legs II • more on Amphibians • land life advantages • more oxygen • prey – arthropods & plants • fewer (no?) predators • sound / sight / balance improvements (terrestrial sensors) • ears and eyes • first amphibians: Devonian (mid Paleozoic) Northwest Tailed Frog

  11. Shelled eggs • Reptiles • amniote eggs with: • extra-embryonic membranes • shells for protection • dry scaly skin • internal fertilization • adult care for young • kidneys conserve water

  12. Reptiles II • Evolved in late Paleozoic (Carboniferous) • Huge diversity – polyphyletic with many long-lived lines from the end of the Paleozoic • Two early lines • Sauropsids – most of the diverse lines • Synapsids – ultimately gave rise to mammals

  13. Birds • Just another reptilian group? • Feathers – insulating, flight (modified scales) • Bones hollow • Beaks • Thermoregulation – high metabolism rates • All adaptations for flight • Patterns of behavior • Elaborate mating behavior • Maternal/paternal care • Migration

  14. Birds II • Evolved from theropod dinosaurs, mid Mesozoic Archaeopteryx lithographica 150 my

  15. Birds III Sinosauropteryx prima 125 my Caudipteryxzoui 125 my

  16. Mammals I • Hair (modified scales) • Milk fed to young • Live young (except for 3 that lay eggs) • Precise teeth that fit together • 3 middle ear bones (derived from jaw bones)

  17. Mammals II • Three major lines • monotremes – egg layers • marsupials – pouched • eutherian – placental Spiny echidna, egg-layer Blue whale, largest mammal Marsupial “mouse”

  18. Mammals IIIA • Evolved in early Paleozoic 200 mya • Adaptive radiation during mesozoic & cenozoic tied to continental drift – see ST Fig 26.2 • End of mesozoic opened habitats • Mammals much more efficient terrestrial forms • Drifting continents isolated mammalian groups on “rafts”

  19. Mammals IIIB Early Triassic Late Triassic • Compare with ST Fig 26.2 * Early Cretaceous Late Cretaceous

  20. Mammals IIIC Modern day mammalian distribution

  21. Mammals IV - Primates Galago • 3 present groups • prosimians – lemurs, galagos • tarsiers • monkeys, apes, humans • Early primates evolved in early Cenozoic from rodent ancestors • 5 features preadapted early primates to modify later in the line toward humans • enhanced vision • upright walking • modifications in hand bones & muscles • generalized teeth • social behavior (& increases in brain capacity and complexity) Tarsier Barbary Macaque

  22. Human evolution • Humans evolved in Africa • Earliest huminoids – mid Cenozoic (25 mya) • cooler climate led to challenges • later radiation of “southern apes” (Australopithecus) 4-3 mya • first appearance of Homo ~ 2.5 mya • Homo erectus leaves Africa ~2 mya • Homo sapiens evolved 150,000 ya • Homo neanderthalensis evolved 250,000 ya; extinct 35,000 • Recent studies show no DNA mixing or carryover of H. n. DNA in modern human lines • Most evidence supports Out of Africa theory rather than multiregionalism • Best site for current status of human evolution facts: http://www.talkorigins.org/faqs/homs/

  23. Human evolution timeline Chart from: http://www.talkorigins.org/faqs/homs/species.htmlInteractive Human Evolution

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