| It has been independently lost or reduced in several amniote lineages, however, including crocodilians, birds, tuataras, iguanian lizards, cetaceans, and catarrhine primates. |
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| Since amniote intromittent organs are hydrostatic, it follows that the wall of their erectile structures must be reinforced with inextensible fibers to prevent aneurysms. |
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| They were the first vertebrates to lay an amniote egg, a new kind of incubator with a hard shell and a number of embryonic membranes. |
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| Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. |
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| Most snakes focus by moving the lens back and forth in relation to the retina, while in the other amniote groups, the lens is stretched. |
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| A time of forests, swamps, seed ferns, mosses, lycopods and the origin of the amniote egg. |
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| Taxonomic congruence versus total evidence, and amniote phylogeny inferred from fossils, molecules, and morphology. |
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| Unlike other mammals, monotremes, like the platypus, never evolved to give live birth, but instead lay eggs like their amniote ancestors. |
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| Two cases of triorchidism have been observed in a rare Malagasy tortoise, Geochelone yniphora, suggesting the phenomenon occurs in at least three deep amniote lineages. |
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| Several researchers have long considered the possibility that the superficially reptile-like features of this animal might tell us something about amniote ancestry. |
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