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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]
Most scientists have concluded that all of the primary groups of modern amphibians—frogs, salamanders and caecilians—are closely related. Some writers have argued that the early Permian dissorophoid Gerobatrachus hottoni is a lissamphibian. [ 2 ]
Most amniotes still require regular access to drinking water for rehydration, like the semiaquatic amphibians do. They have better homeostasis in drier environments, and more efficient non-aquatic gas exchange to power terrestrial locomotion , which is facilitated by their astragalus.
The world’s frogs, salamanders, newts and other amphibians remain in serious trouble. A new global assessment has found that 41% of amphibian species that scientists have studied are threatened ...
Class Amphibia (amphibians, some ancestral to the amniotes)—now a paraphyletic group; Class Synapsida (mammals and their extinct relatives) Class Sauropsida (reptiles and birds) While this traditional taxonomy is orderly, most of the groups are paraphyletic, meaning that the structure does not accurately reflect the natural evolved grouping. [47]
[17] [18] Unlike other modern amphibians (frogs and salamanders) the skull is compact and solid, with few large openings between plate-like cranial bones. The snout is pointed and bullet-shaped, used to force their way through soil or mud. In most species the mouth is recessed under the head, so that the snout overhangs the mouth. [10]
The most general characteristic of molluscs is they are unsegmented and bilaterally symmetrical. [16] The following are present in all modern molluscs: [ 17 ] [ 19 ] The dorsal part of the body wall is a mantle (or pallium) which secretes calcareous spicules , plates or shells.
Temnospondyli (from Greek τέμνειν, temnein 'to cut' and σπόνδυλος, spondylos 'vertebra') or temnospondyls is a diverse ancient order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian and Triassic periods, with fossils being found on every continent.