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Not all paleontologists today are convinced that Lissamphibia is indeed a natural group, as there are important characteristics shared with some non-lissamphibian Palaeozoic amphibians. Currently, the two prevailing theories of lissamphibian origin are: Monophyletic within Temnospondyli [15] Monophyletic within Lepospondyli [3]
The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus) [41] but this is a great deal smaller than the largest amphibian that ever existed—the extinct 9 m (30 ft) Prionosuchus, a crocodile-like temnospondyl dating to 270 million years ago from the middle Permian of Brazil. [42]
Amphisbaenia / æ m f ɪ s ˈ b iː n i ə / (called amphisbaenians or worm lizards) is a group of typically legless lizards, [2] comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes.
The event is well-documented [1] and important [2] [3] academically as a demonstration of transitional forms and exaptation, the re-purposing of existing structures during evolution. [ 4 ] The ossicles evolved from skull bones present in most tetrapods , including amphibians , sauropsids (which include extant reptiles and birds ) and early ...
A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
Zoologists characterize amniotes in part by embryonic development that includes the formation of several extensive membranes, the amnion, chorion, and allantois. Amniotes develop directly into a (typically) terrestrial form with limbs and a thick stratified epithelium (rather than first entering a feeding larval tadpole stage followed by ...
External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside the pharynx and covered by gill slits, as they are in most fishes. Instead, the respiratory organs are set on a frill of stalks protruding from the sides of an animal's head. The axolotl has three pairs of external ...
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.