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Amphibians areectothermic,anamniotic,four-limbedvertebrateanimals that constitute theclassAmphibia. In its broadest sense, it is aparaphyletic group encompassing alltetrapods, but excluding theamniotes (tetrapods with anamniotic membrane, such as modernreptiles,birds andmammals). Allextant (living) amphibians belong to themonophyleticsubclassLissamphibia, with three livingorders: Anura (frogs andtoads), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostlysemiaquatic, amphibians have adapted to inhabit a wide variety ofhabitats, with most species living infreshwater,wetland orterrestrial ecosystems (such asriparian woodland,fossorial and evenarboreal habitats). Theirlife cycle typically starts out asaquaticlarvae withgills known astadpoles, but some species have developed behavioural adaptations to bypass this.
Young amphibians generally undergometamorphosis from an aquatic larval form with gills to an air-breathing adult form withlungs. Amphibiansuse their skin as a secondary respiratory interface, and some small terrestrialsalamanders and frogs even lack lungs and rely entirely on their skin. They are superficially similar toreptiles likelizards, but unlike reptiles and otheramniotes, require access to water bodies to breed. With their complex reproductive needs and permeable skins, amphibians are oftenecological indicators to habitat conditions; in recent decades there has been a dramaticdecline in amphibian populations for many species around the globe.
The earliest amphibiansevolved in theDevonian period fromtetrapodomorphsarcopterygians (lobe-finned fish witharticulatedlimb-likefins) that evolved primitive lungs, which were helpful in adapting to dry land. They diversified and became ecologically dominant during theCarboniferous andPermian periods, but were later displaced in terrestrial environments by early reptiles andbasalsynapsids (predecessors of mammals). The origin of modern lissamphibians, which first appeared during the Early Triassic, around 250 million years ago, has long been contentious. The most popular hypothesis is that they likely originated fromtemnospondyls, the most diverse group of prehistoric amphibians, during the Permian period. Another hypothesis is that they emerged from lepospondyls. A fourth group of lissamphibians, theAlbanerpetontidae, became extinct around 2 million years ago. (Full article...)
Heleophrynidae is afamily offrogs, commonly known asghost frogs. They are thought to be the mostbasal group in theNeobatrachia. The family consists of twogenera,Heleophryne andHadromophryne, with seven species. Ghost frogs live in swift-moving mountain streams inSouth Africa. The common name of "ghost frogs" may have been coined because of their occurrence inSkeleton Gorge. (Full article...)
TheCryptobranchoidea are asuborder ofsalamanders found in Asia, European Russia, and the United States. They are known asprimitive salamanders, in contrast toSalamandroidea, theadvanced salamanders. It has two living subdivisions,Cryptobranchidae (Asian giant salamanders andhellbenders), andHynobiidae, commonly known as Asian salamanders.
Giant salamanders are obligate paedomorphs with partial metamorphosis, but Asiatic salamander goes through a full metamorphosis. The only known exceptions are theLongdong stream salamander, which has been documented as facultatively neotenic, and theEzo salamander, where a now assumed extinct population from Lake Kuttarush in Hokkaido had neotenic traits like gills in adults.
The oldest members of the group are known from theMiddle Jurassic (Bathonian) agedYanliao Biota of China. (Full article...)
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Afrog is any member of a diverse and largelysemiaquatic group of short-bodied,taillessamphibianvertebrates composing theorderAnura (coming from theAncient Greekἀνούρα, literally 'without tail'). Frog species with roughskin texture due towart-likeparotoid glands tend to be calledtoads, but the distinction between frogs and toads is informal and purely cosmetic, not fromtaxonomy or evolutionary history.
Frogs are widely distributed, ranging from thetropics tosubarctic regions, but the greatest concentration ofspecies diversity is intropical rainforest and associatedwetlands. They account for around 88% of extant amphibian species, and are one of the five most diversevertebrate orders. The oldest fossil "proto-frog"Triadobatrachus is known from theEarly Triassic ofMadagascar (250 million years ago), butmolecular clock dating suggests theirdivergence from other amphibians may extend further back to thePermian, 265 million years ago.
Adult frogs have a stout body, protrudingeyes, anteriorly-attachedtongue, limbs folded underneath, and notail (the "tail" oftailed frogs is an extension of the malecloaca). Frogs haveglandular skin, withsecretions ranging from distasteful to toxic. Their skin varies in colour from well-camouflaged dappled brown, grey and green, to vivid patterns of bright red or yellow and black to show toxicity andward off predators. Adult frogs live in bothfresh water and on dryland; some species are adapted forliving underground orin trees. As their skin issemi-permeable, making them susceptible todehydration, they either live in moistniches or have specialadaptations to deal with drier habitats. Frogs produce a wide range ofvocalisations, particularly in theirbreeding season, and exhibit many different kinds of complexbehaviors to attract mates, to fend off predators and to generally survive. (Full article...)
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Dendrophryniscus is a genus oftrue toads in the familyBufonidae, sometimes known astree toads. They areendemic to theAtlantic Forest of Brazil. (Full article...)
Dermophis is a genus of worm-likeamphibians in the familyDermophiidae, the Neotropical and Tropical African caecilians. They are found in theMiddle America between southernMexico and northwesternColombia. Common namesMexican caecilians orNeotropical caecilians are sometimes used for them. (Full article...)
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