BIOL 202 Lecture Notes - Lecture 14: Shoulder Girdle, Ellesmere Island, Appendicular Skeleton
1 Mar 2016
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Lecture 4 vertebrate transition to land: origins of. Periods of local drought and appearance of land. Lobe-finned fish have unique pectoral and pelvic girdles (appendicular skeleton) Sarcopyterygians did not walk , used fins to maneuver. Polypterus sengalus experiment: does way it is raised affect locomotive behaviour, fins closer into body axis and head held higher in those that could walk on land. No medium for gamete transport or zygote development. Coelocanth not direct ancestor of first tetrapod. Rhipidistians probable ancestor: fins have multibone features (homologous with eventual arm structure, hinged brain case, labryrinthodonts teeth in jaws, outside enamel folded on teeth. Peak abundance in carboniferous but poor fossil record. Tetrapod features: ossified vertebral arches, hinged braincase, labryrinthodont teeth. Snap/grab jaw mechanism and moveable head: late devonian, rhipidistian-like. Ichthyostega: 1932, east greenland, s ve-s derbergh, erik jarvik, skull similar to sarcopyterygians. Skull hinged to vertebral column (mobility in neck)
