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VERTEBRATES IN HISTORY

VERTEBRATES IN HISTORY. VERTEBRATES. 50,000 known species of vertebrates More than half are fishes. Major Eras of Vertebrate Development. Oldest:Paleozioc (286-600 mya ) Middle :Mesozoic (145-250 mya ) Youngest: Cenozoic (65 mya - present). How to Read Table 4.2. Bottom is longer ago

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VERTEBRATES IN HISTORY

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  1. VERTEBRATES IN HISTORY

  2. VERTEBRATES • 50,000 known species of vertebrates • More than half are fishes

  3. Major Eras of Vertebrate Development • Oldest:Paleozioc (286-600 mya) • Middle :Mesozoic (145-250 mya) • Youngest: Cenozoic (65 mya- present)

  4. How to Read Table 4.2 • Bottom is longer ago • Point is where organism(s) first appeared • Width of bubble shows size of population • Wide: big population; Narrow: small population • First group is jawless fish • Devonian Period is age of fishes

  5. 450 million years ago… • First fishes appeared in fresh water • Don’t know what it is… • We only know it is there because of fossil record • Appeared in the Paleozoic Era • Known as “UNKNOWN FISH”

  6. 400 million years ago… • Still in Paleozoic Era • Ostracoderms appeared • Jawless • Class Agnatha, Order Ostracodermi • Extinct • Heterocercal Tail (shape): Top lobe larger than bottom lobe; drives head down

  7. Ostracoderms • Oldest known vertebrates • Covered with bony dermal armor • Skeleton made of little bone/ mostly cartlidge • External gill slits • Origin is unknown

  8. 350 million years ago • Ostracoderm became extinct • Possibly because of competition • Possibly replaced by other jawless fish

  9. 300 million years ago • 1968, fossils of lampreys found (at least 300 million yrs old) • Order: Cyclostomata (hagfish and lamprey) • Lamprey has no bone, little cartilidge • 6 gill slits • Best External Characteristics: Jawless • Best Internal Characteristics: Notochord • Ancestors: • Ostracoderm: lamprey • Unknown: both

  10. Placoderm • Freshwater fish • Different numbers of appendages • Anterior: Head; Posterior: Tail End • Axial Skeleton: Middle part • Appendicular Skeleton: Outside parts • Girdle: connecting pieces

  11. Pectoral Girdle Appendicular Skeleton Axial Skeleton Pelvic Girdle

  12. Placoderm Taxonomy • Kingdom: Animalia • Phylum: Chordata • Subphylum: Vertebrata • Class: Placodermii • SubClass: Acanthodii • Gave rise to modern jawed fish

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