Earth Sciences 2266F/G Lecture Notes - Lecture 7: Cladodont, Mangiafuoco, Endoskeleton
23 Jan 2020
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Chondrichthyes- sharks & relatives jawed vertebrates w/skeleton made of cartilage (rather than bone) Fossil record of chondrichthyes low preservation (cartilaginous skeletons: most of record is teeth/denticles (placoid or bony scales, teeth have 3 cusp: middle large and 2 small on the side. Hard parts: sharks have mineralized teeth (central pulp cavity surround by dentine, cover by enamel) Point of of scales backwards to body, helps with streamline: endoskeleton composted of cartilage and calcified cartilage (strengthen by layers of tile- like hydroxyapatite) *not true bone. General features: cartilaginous skeleton derived from notochord via segmentation of backbone lack ribs (larger species can collapse when out of water) Lorenzini: sensing organs (pores) to sense electric field for predation. Radiations of chondrichthyes: first radiation: carboniferous, when chimeras appeared, second radiation: jurassic, modern sharks/rays, sharks live both marine/freshwater (range of habitats) Stem elasmobranchs: well preserved, simplest form of shark (basic body) For catch/hold prey but not efficient in slicing.
