8-The_transition_to_land

8-The_transition_to_land - The Transition to Land:...

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The Transition to Land: Sarcopterygii Part II Lec.8 – Chap.11 DOF
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Assignment 1 Numerical grades are on-line Capitalize common names In text citations (author,yr). Make a poster Why did I ask you to use Catalog of Fishes
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The Transition to Land: Sarcopterygii Part II Lec.8 – Chap.11 DOF
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Acanthodi i Sarcopterygii Actinopterygii
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Tetrapodamorphs (Sarcopterygii) Appeared with dipnoans in the Devonian, most disappeared by the end of the Permian Most were large predatory fishes (up to 4m) living in shallow freshwater habitats Had sarcopterygian features of having a jointed (kinetic) skull; lobed fins, and replacement teeth on the jaw margins
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Osteolepidiforms (Sarcopterygii:Tetrapodamorphs ) Eustenopteron foordi – close to the direct ancestor of tetrapods but unlikely to have moved on to land Shows trends of tetrapodamorphs transitions including reduction in dermal bone thickness and transition to symmetrical caudal fins
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The transition to land. Why breath air? Why would limb bones be useful in the water? Why move on to land? Why did it take 100 my?
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Osteolepidiforms (=Rhipidistians) (Sarcopterygii:Tetrapodamorphs) Primarily predators in shallow, freshwater habitats 2 dorsal fins teeth on jaw margins lobed fins jointed skulls (intercranial) choanae (the internal nostrils) Eustenopteron , Late Devonian
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Fig 11.14 Eustenopteron Key traits that characterized the Sarcopterygian ancestors of tetrapods: an intercranial joint, arrangement of the dermal bones, axial elements of the pectoral fin skeleton.
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Elpistostegalians (Sarcopterygii:Tetrapodamorphs ) Closest relatives of tetrapods Homologies including: eye position (both have upward facing eyes set close together, with eyebrow ridges) skull roof bones (frontals, parietals, nasals) paired fins (humerus, radius, ulna; femur, tibia, fibula) Have well developed lungs dentition (infoldings of the dentine) Vertebral acccesories (ossified neural spines, from ring shaped centra)
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Fig 11.15 (a) Eustenopteron ,(b) Ichthyostega ,(c) Neoceratodus
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This note was uploaded on 09/13/2010 for the course BIOL 4145 taught by Professor Chakrabarty during the Fall '09 term at LSU.

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8-The_transition_to_land - The Transition to Land:...

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