Earth Sciences 2266F/G Lecture Notes - Lecture 10: Shoulder Girdle, Tiktaalik, Spiral Bevel Gear
7 Feb 2020
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Document Summary
Share tooth features with labyrinthodont teeth: evolutionary connection b/w lobe-fin and tetrapods, humeris, radius, ulna found in both groups. Skull modifications: tiktaalik flat, triangular (like tetrapods, gill arches and internal nostril (suggest lung breathing, what made them fish like was scales. Origin of neck: fish to tetrapod, cheekbones were lost. Pectoral in lobe fish are fused to back of skull: tetrapods, pectoral girdle separate from back of skull (space) *tiktaalik confirms detachment of shoulder girdle from skull. Development of neck: amphibians have neck b/w head and shouldners. Allow movement of head (raise out of water to breath) formation of thick ribs (fish have thin ribs cause supported by water) Upper bone of hypoid arch: size/position of hyomandibular is intermediate to osteolepid/tetrapod. Hyo becomes reduce in size and migrates towards head (become stapes) Pectoral girdle: pectoral in tikaalik better developed than fishes (support of hind area) However, pectoral hip girdle not attached to vertebral (like fish have weaker hind than forelimbs)
