BIOL 204 Lecture 8: lecture 8
Document Summary
Jaws: phylogenetic trends: consider, what components of the skull form the upper and lower jaw, type of jaw suspension present? (how are jaws attached to the rest of the skull. Paleostyly: earliest ancestral vertebrates did not have jaws, all of the brachial arches were used to support gilds, extant agnathans. Hyostyly: palatoquadrate does not attach directly to the chondocranium, mobile joint between hyomandibula and the chondocranium and between the. Jaws suspended from chondocranium by hyomandibula hyomandibula and the jaws: hyomandibula forms a swinging bridge that allows the jaws to swing forward, more extant sharks, palatoquadrate forms upper jaw, meckel"s cartilage for(cid:373)s lower jaw. Feeding mechanisms- elasmobranchii: hyostylic jaw suspension allows for protrusion, allows mouth to open wider and close faster. Lecture 8: allows upper and lower jaws to strike the prey at the same time- grip prey securely. In most elasmobranchii (except 6-gilled sharks) only a reduced pharyngeal slit- Spircale- remains between the hyoid an the mandibular arches.
