BIOL 330 Lecture Notes - Lecture 5: Dwarf Lanternshark, Electroreception, Whale Shark
14 Feb 2017
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Document Summary
With anal fins, 5-7 gill slits) shallow, warm waters: squalomorpha (162 shark spp. Without anal fins) deep waters: batoidea (638 ray/skate spp. , 5 gill slits, chimaeriformes (49 deepwater spp. , 1 gill slit) Have a mosaic of ancestral and derived characteristics: Ancestral characteristics: terminal mouth, dentition (some lineages, calcified skeletons (some line, fin structure (some lineages) Derived characteristics: subterminal mouth, dentition (some lineages, loss of bone (lightening of the body, cartilaginous vertebral centra, parallel evolution of fins and tail structure (in some lineages) Unique tooth replacement: each took on the functional edge of the jaw is part of a tooth whorl attached to a ligamentous band that inserts deep in the jaw (rapid displacement 8 days) Many sharks have a heterocercal tail: tip of the vertebral column turns upwards, extending into the dorsal lobe of the tail fin; dorsal lobe is often larger than the ventral lobe, produces a forward and upward thrust.
