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Unformatted text preview: Class Mammalia Mammalia: 4,600 species, mamma=breast: mammals nourish their young with milk, fossil record extends back to early Jurassic En dothermy-improves greater energy demands than ectothermy, therefore, endotherms must:-process food more effectively, aquire more oxygen, circulate blood more effectively, insulate themselves against heat loss, dissipate heat when they are extremely active Overv iew of subclass Synapsidamamma l-l i ke rept i les What were t he early mamma ls do i ng before d i nos became ext i nct?-many were probably nocturnal predators that fed on insects: allowed them to avoid predators-required them to: hear prey and predators well, process food more effectively-develop good endothermic capabilities: hair for insulation, improved circulation, improved respiration-improved maternal care of young What featu res d i d mamma ls have tha t perm i t ted them to surv ive the ha rsh t i mes that k i l led the d i nos?-the same features that they had perfected as small, nocturnal, predators Ma m ma l Featu res-skull features: resulted in better chewing ability and better hearing ability-transformation of jaw articulation: zygomatic arch, condyle, coronoid process-synapsid reptile: only chew up and down-mammals have better chewing ability, possible because of sliding chondyle zygomatic arch Tooth Mod i f icat ion Reptiles: unicuspid (one point) teeth...
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- Fall '07