FNR 24000 Lecture 20: FNR lecture 20
22 Oct 2018
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Document Summary
A widely misunderstood group of animals, often out casted. Reptiles are ectothermic tetrapods that possess amniotic eggs and scales or scutes. Limblessness has evolved at least 25 times in reptiles, with snakes only representing on such origin. After years of research, it is still unclear where turtles should be placed in the phylogeny. Reptiles first appeared in the fossil record 310-320 million years ago (late carboniferous) These early species were the first tetrapods to evolve key adaptations for life on dry land (modifications to eggs and skin) Not homologous to bony, dermal fish scales. In crocodilians, scales remain throughout life, grow gradually to replace wear. In snakes and lizards, new scales grow beneath old and old scales are shed. Turtles add new layers of keratin under old layers of the plate-like scutes (modifies scales) Critical for invasion of land-breaks the need for moisture to prevent egg desiccation (leathery or calcareous shells)
