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Amnioten. Amnioten (Amniota), auch Amniontiere oder Nabeltiere genannt, sind eine Großgruppe der Landwirbeltiere (Tetrapoda). Ihre Vertreter sind vor allem durch die Fähigkeit gekennzeichnet, sich, anders als Amphibien, völlig unabhängig vom Wasser fortzupflanzen. Statt über eine kurze Embryonalphase mit anschließendem frei lebenden voll ...
Westlothiana lizziae. Smithson and Rolfe, 1990. Westlothiana ("animal from West Lothian") is a genus of reptile -like tetrapod that lived about 338 million years ago during the latest part of the Viséan age of the Carboniferous. The genus is known from a single species, Westlothiana lizziae.
The amnion is a feature of the vertebrate clade Amniota, which includes reptiles, birds, and mammals. Amphibians and fish lack the amnion and thus are anamniotes (non-amniotes). The amnion stems from the extra-embryonic somatic mesoderm on the outer side and the extra-embryonic ectoderm or trophoblast on the inner side. [1]
23 de mai. de 2018 · amniote A vertebrate whose embryos are totally enclosed in a fluid-filled sac – the amnion. The evolution of the amnion provided the necessary fluid environment for the developing embryo and therefore allowed animals to breed away from water. Amniotes comprise the reptiles, birds, and mammals. Compare anamniote. A Dictionary of Biology.
The amniotic sac starts to form and fill with amniotic fluid just days after a woman gets pregnant. [1] At first, the amniotic fluid is made from the mother's plasma (the liquid part of her blood ). [2] At first, the amniotic fluid is made mostly of water with electrolytes (salts). However, by the 12th to the 14th week of pregnancy, proteins ...
Eunotosaurus ( Latin: Stout-backed lizard) is an extinct genus of amniote, possibly a close relative of turtles. Eunotosaurus lived in the late Middle Permian ( Capitanian stage) and fossils can be found in the Karoo Supergroup of South Africa. Eunotosaurus resided in the swamps of what is now southern Africa. [1]
The amniote egg includes a series of extraembryonic membranes that surround the developing embryo and provide all the nutritional, waste disposal, and gas exchange requirements during development. In reptiles (including birds) and the Monotremata (basal mammals), the embryo and extraembryonic membranes are encapsulated in an egg with either a leathery exterior or a hard shell.
