ZOO-3713C Study Guide - Midterm Guide: Osteostraci, Placodermi, Appendicular Skeleton
21 Jan 2017
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Cellular bone: cells in the bone matrix means that the skeleton can be easily removeled during growth (in matrix; the bone marrow and lamella) Heterocercal tail: a caudal fin in which the vertebral axis turns upward into an enlarged dorsal lobe to provide greater upward thrust possibly related to the lateral line system. Osteostracoderms (the paleozoic jawless fishes) and more derived. 3 dorsal cephalic fields: on the dorsal surface of the head and consisting of groups of small plates underlain by canals for branches of cranial nerves. Jaws: evolved from deep ventral articulated (jointed) mandibular gill arches next to the pharyngeal cavity. 3 semicircular canals: horizontal one added for pitch/roll/yaw. Appendicular skeleton: the pectoral fins have pectoral girdles in the shoulder and pelvic appendages (attachment sites) Optic pedicel: a stalk with a cup shaped end to support the eye. Placoid scales: consist of an acelluar, bony base (b), that supports a thorn shaped dentile(g)
