BISC 316 Lecture 8: Lecture 8 Vert. Bio

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 316
• Professor: Tammy Mc Mullan

Document Summary

4 clades of gnathostomes: placoderms, acanthodians, chondrichthyes, osteichthyes. Teeth in replacement families: teeth have been growing to replace tooth replacement families. Spiracle: uses liver for buoyancy liver slightly less dense than salt water allows them to be. No lungs or air bladders: have claspers for reproduction. First elasmobranchii occurred in the late ordivician. 3 major radiations elasmobranchii: paleozoic, early mesozoic, extant radiation (triassic) Changes to teeth, jaws, jaw suspension, fins: paleozoic early (cid:862)sharks(cid:863) (cid:862) te(cid:373) cho(cid:374)dri(cid:272)hthyes(cid:863) No attachment: second radiation early mesozoic (cid:862)ste(cid:373) elas(cid:373)o(cid:271)ra(cid:374)(cid:272)hii(cid:863) Many jurassic and cretasceous genera extant (cid:862)(cid:373)oder(cid:374)(cid:863) appeara(cid:374)(cid:272)e (cid:271)y jurassic. Hyostylic jaw suspension: upper jaw attached loosely to cranium by ligaments, articulation between jaw, cranium, and hyomandibular, protrusible jaw. Teeth: single cusp of flat crown. During jurassic, elasmobranchii split into two groups: selachii, batoidea. 3 taxa of chondrichthyes selachii, batoidea, chimaeiformes. Red riding hood principle (cid:862)(cid:271)etter to eat you (cid:449)ith(cid:863)