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dermal structures



Just read Tom Hopp`s mention of "one time" evolution of dermal scutes, follicles etc., I myself have a strong feeling about a once only development of warm-bloodedness, and that being mainly for the incubation of the young in a colder enviorn. In fact, I`m looking at endothermy before the synapsid-diapsid split. (I don`t believe we should place diapsid beginnings way after synapsid development based upon the scant fossil record of early diapsid forms). Endothermy is complex, involving many organ systems, and requires large expenditure of energy. It would be hard for a new form to develop it independently, when already established in existing species due to competition. So...I think it evolved only once, and that diapsids probably are derived from the synapsid condition. And feathers, as well as hair, or at least "fuzzy scales" would soon follow. (so we`re talking Pennsylvanian).