Earth Sciences 2266F/G Lecture Notes - Lecture 9: Swim Bladder, Labyrinthodontia, Walking Fish
7 Feb 2020
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Sacropterygii-lobe finned fishes fin supported by single basal bone join body via single bone: enamel on teeth, lungs (don"t know if its true lungs) intracranial join dividing parietal/postparietal bones, swim bladder w/oil and live birth. Diverse, peak in carboniferous than extinct loss maxilla, 3 lobe tail (triangular), live young, fatty lung (like swim bladder) Latimeria (walking fish): slow, propelled paired fishes like walking: dipnoi (lungfish) Found in marine, switch to freshwater to reduce competition (found today: have 2 lungs for air breathing (when ponds dry out) Structure lack maxilla nd pre-maxilla (left with back part of mouth: crushing tooth plates. Lung breathing internal nostrils for air, ribs expand for air gulping : modification of swim bladder to lungs. Osteolepida internal nostrils (air breathers) limb bones homologous to landliving humerus, radius, ulna. Panderichthyida labyrinthodont teeth flattened head/body: humerus oriented at right angle to body. Early tetrapods (acanthostega: developed caudal fin, gills, ear region, 7-8 digits and well defined wrist joint.
