Earth Sciences 2266F/G Lecture Notes - Lecture 11: Swim Bladder, Hyomandibula, Shoulder Joint
7 Feb 2020
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Forelimbs & pectoral girdle: fishpods already had strong limbs which further strengthen limb bones need further modified for support. Forelimb: shoulder joint modified to allow humerus to stick out lengthen arm bones and elbow joint allow radius/ulna orient down. Pectoral girdle: more robust to bear more weight. Pelvic girdle: attach to sacral vertebra of backbone to bear weight of posterior part of body. Digits: standard is 5 (but earlier tetra had up to 8: allow support in air (stronger to drag), in water (bigger paddle) Trot: stimultaneous contact with ground of diagonally opposing limb. Tripodal: tail acts as third point of support. Centrum: bony disk, forms around and replaces notochord. Morphological adaptations: development of stronger bones of centrum (fuse to form centrum, development of zygapophysal processes (make vertebrae interlock) Allow bend without sagging: breathing: gill must be replaced by lung breathing. Effective in picking low frequency vibration in water but need to modify for air.
