Examples of amniote in the following topics:
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- The distinguishing characteristic of amniotes, a shelled egg with an amniotic membrane, allowed them to venture onto land.
- The amniotes, reptiles, birds, and mammals, are distinguished from amphibians by their terrestrially-adapted egg, which is protected by amniotic membranes.
- The evolution of amniotic membranes meant that the embryos of amniotes were now provided with their own aquatic environment, which led to less dependence on water for development, allowing the amniotes to branch out into drier environments.
- The amniotic egg is the key characteristic of amniotes .
- The key features of an amniotic egg are the chorion, amnion, and allantois.
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- Modern amniotes, which includes mammals, reptiles, and birds, evolved from an amphibian ancestor approximately 340 million years ago.
- The first amniotes evolved from their amphibian ancestors approximately 340 million years ago during the Carboniferous period.
- The early amniotes diverged into two main lines soon after the first amniotes arose.
- In the past, the most common division of amniotes has been into the classes Mammalia, Reptilia, and Aves.
- This chart shows the evolution of amniotes.
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- Dinosaurs and pterosaurs diverged from early amniotes and dominated the Mesozoic Era.
- One of the oldest-known amniotes is Casineria, which had both amphibian and reptilian characteristics.
- Soon after the first amniotes appeared, they diverged into three groups (synapsids, anapsids, and diapsids) during the Permian period.
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- For example, the phylogenetic tree shows that lizards and rabbits both have amniotic eggs, whereas frogs do not; yet lizards and frogs appear more similar than lizards and rabbits.
- A tree may not indicate how much time passed between the evolution of amniotic eggs and hair.
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- For example, all of the organisms in the orange region evolved from a single ancestor that had amniotic eggs .
- Consequently, all of these organisms also have amniotic eggs and make a single clade, also called a monophyletic group.
- Now, consider the amniotic egg characteristic in the same figure .
- Lizards, rabbits, and humans all descend from a common ancestor that had an amniotic egg.
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- At some point, the amniotic sac bursts and the amniotic fluid escapes.
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- Tetrapods can be further divided into two groups: amphibians and amniotes.
- Amniotes are animals whose eggs are adapted for terrestrial living; this group includes mammals, reptiles, and birds.
- Amniotic embryos, developing in either an externally-shelled egg or an egg carried by the female, are provided with a water-retaining environment and are protected by amniotic membranes.
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- Class Reptilia, amniotes that are neither mammals nor birds, has four living clades: Crocodilia, Sphenodontia, Squamata, and Testudine.
- A reptile is any amniote (a tetrapod whose egg has an additional membrane, originally to allow them to lay eggs on land) that is neither a mammal nor a bird.