Temporal range: Early Carboniferous – present,
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Batrachomorpha
Class: Amphibia
Gray 1825[2]
Many amphibians—like this Ceratophrys cranwelli—exhibit biofluorescence.[3]

Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.

The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles like lizards, but unlike reptiles and other amniotes, require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in recent decades there has been a dramatic decline in amphibian populations for many species around the globe.

The earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods, but were later displaced by reptiles and other vertebrates. The origin of modern amphibians belonging to Lissamphibia, which first appeared during the Early Triassic, around 250 million years ago, has long been contentious. However the emerging consensus is that they likely originated from temnospondyls, the most diverse group of prehistoric amphibians, during the Permian period.[4]

The three modern orders of amphibians are Anura (the frogs), Urodela (the salamanders), and Apoda (the caecilians). A fourth group, the Albanerpetontidae, became extinct around 2 million years ago. The number of known amphibian species is approximately 8,000, of which nearly 90% are frogs. The smallest amphibian (and vertebrate) in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just 7.7 mm (0.30 in). The largest living amphibian is the 1.8 m (5 ft 11 in) South China giant salamander (Andrias sligoi), but this is dwarfed by prehistoric temnospondyls such as Mastodonsaurus which could reach up to 6 m (20 ft) in length.[5] The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology.

  1. ^ "Amphibia". Retrieved May 24, 2022.
  2. ^ Cite error: The named reference BlackburnWake was invoked but never defined (see the help page).
  3. ^ Lamb, Jennifer Y.; Davis, Matthew P. (February 27, 2020). "Salamanders and other amphibians are aglow with biofluorescence". Scientific Reports. 10 (1): 2821. Bibcode:2020NatSR..10.2821L. doi:10.1038/S41598-020-59528-9. ISSN 2045-2322. PMC 7046780. PMID 32108141. S2CID 257031840. Wikidata Q89930490.
  4. ^ Atkins, Jade B.; Reisz, Robert R.; Maddin, Hillary C. (March 22, 2019). "Braincase simplification and the origin of lissamphibians". PLOS ONE. 14 (3): e0213694. Bibcode:2019PLoSO..1413694A. doi:10.1371/journal.pone.0213694. ISSN 1932-6203. PMC 6430379. PMID 30901341. ...there has been a growing consensus that lissamphibians are a monophyletic assemblage derived from within Temnospondyli, and more specifically from within the amphibamid dissorophoids.
  5. ^ "Back to school: temno superlatives". Bryan Gee, PhD. Retrieved June 29, 2022.

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