BIOL 3114 Lecture Notes - Lecture 8: Shoulder Girdle, Ellesmere Island, Osteolepiformes
20 Oct 2016
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Document Summary
Osteolepiformes extinct fleshy-finned fishes adapted for shallow water: heavily scaled, large heads, enamel of teeth folded inward (labyrinthodont) Similar to osteolepiformes but: flatter body, elevated eyes, loss of dorsal and anal fins, mid-devonian (~385 mya) Tiktaalik rosaeae fishapod: described 2006, late devonian ~385 mya from ellesmere island, canada, intermediate between sarcopterygians and tetrapods, key features of tiktaalik. Pectoral girdle separate from skull: had neck. Pectoral fins heavy and muscular, with digits and flexible wrist. Stem tetrapods ichthyostega and acanthostega, ventastega: late devonian ~365 mya, heavy limbs with multiple (7-8) toes, some with internal fish-like gills based on arterial supply to ceratobranchials. Anthracosaurs gave rise to amniotes (reptiles, birds, and mammals) Temnospondyls possibly gave rise to modern amphibians. Relationship to other tetrapods is uncertain, may be polyphyletic. Mostly terrestrial, with some secondarily aquatic forms. First forms in carboniferous (possibly only 20 million years after first tetrapods) Began to dominate terrestrial habitats by mid-permian.
