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Quick Reference. The type of egg produced by reptiles, birds, and prototherian (egg-laying) mammals (amniotes), in which the embryo develops inside an amnion. The shell of the egg is either calcium-based or leathery. From: amniotic egg in A Dictionary of Biology ». Subjects: Science and technology — Life Sciences.
Amniote Egg. The amniotic egg was an evolutionary invention that allowed the first reptiles to colonize dry land more than 300 million years ago. Fishes and amphibians must lay their eggs in water and therefore cannot live far from water. But thanks to the amniotic egg, reptiles can lay their eggs nearly anywhere on dry land.
amniotic egg The type of egg produced by reptiles, birds, and prototherian (egg-laying) mammals (amniotes), in which the embryo develops inside an amnion. The shell of the egg is either calcium-based or leathery. Source for information on amniotic egg: A Dictionary of Biology dictionary.
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Amniotes comprise all fully terrestrial vertebrates and include extant squamates, turtles, crocodiles, birds and mammals. The origin of amniotes, tightly linked to the amniotic egg as a key innovation, represents a major transition in the evolutionary history of tetrapods. Amniotes first appeared in the fossil record about 318 million years ago and their early evolution, diversification ...
12 de mar. de 2021 · Amniotic eggs are multifunctional structures that enabled early tetrapods to colonize the land millions of years ago, and are now the reproductive mode of over 70% of all terrestrial amniotes. Eggshell morphology is at the core of animal survival, mediating the interactions between embryos and their environment, and has evolved into a massive diversity of forms and functions in modern reptiles.
Most mammals do not lay eggs (except for monotremes such as the echidnas and platypuses). Instead, the embryo grows within the mother’s body, with the placenta derived from two of the extraembryonic membranes. Characteristics of Amniotes. The amniotic egg is the key characteristic of amniotes.
