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| | Amniota |
 | | The amniotic egg, together with a penis for internal fertilization, loss of a free-living larval stage in the life cycle, and the ability to bury their eggs, enabled amniotes to escape the bonds that confined their ancestors' reproductive activities to aquatic environments. |
 | | It has been suggested that the original function of the extra-embryonic membranes of the amniotic egg was to facilitate interactions between the mother and the embryo (Lombardi, 1994), but this hypothesis is not supported by the distribution of extended embryo retention in vertebrates, according to most proposed phylogenies (Laurin & Girondot, 1999). |
 | | Placental mammals, for example, have suppressed the egg shell and yolk sac, and elaborated the amniotic membranes to enable nutrients and wastes to pass directly between mother and embryo. |
| tolweb.org /Amniota/14990 (2591 words) |
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