>>Hmm.. I'd have to disagree. Mammals are ancestors of synapsid reptiles like Pelycosaurs. (The ones with the big sails on their backs.) All synapid reptiles are now extinct, the only synapsids that remain are mammals.

>>

>>I guess what I should have said is that mammals and birds are the descendants of reptiles.

>>-----

>>~Melissa

>>1.0 Ambanja Panther (Diesel)

>>0.1 African Hegdehog (Kaimah)



Melissa,



Phylogenetically, the synapomorphies of Amniota are the amniotic egg and the axis (modified second cervical vertebra). At this point, Amniota splits into Reptilia and Mammalia. Mammalia is defined by the presense of hair, mammary glands, incus and maleius, heterodont dentition, the 4 chambered heard, muscular, thoracic diaphrahm and a single bone in the lower jaw (the dentary). Reptilia is defined by the production of uric acid as an excretory product, temperature-dependent sex determination and beta keratin. Reptilia splits into Chelonia and Sauria. Sauria splits into Lepidosaura (Squamata and Sphenodon) and Archosauria (Crocodylia and Aves). Thats according to Pough et al. and Gergus and Schuett.



Chris
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Chris Anderson

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