Amphibia in its widest sense ( sensu lato) was divided into three subclasses, two of which are extinct: Traditionally, the class Amphibia includes all tetrapod vertebrates that are not amniotes. The term was initially used as a general adjective for animals that could live on land or in water, including seals and otters. The word amphibian is derived from the Ancient Greek term ἀμφίβιος ( amphíbios), which means 'both kinds of life', ἀμφί meaning 'of both kinds' and βιος meaning 'life'. The dime is 17.9 mm in diameter, for scale The world's smallest known vertebrate, Paedophryne amauensis, sitting on a U.S. The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology. 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 metres in length. 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 number of known amphibian species is approximately 8,000, of which nearly 90% are frogs. A fourth group, the Albanerpetontidae, became extinct around 2 million years ago. The three modern orders of amphibians are Anura (the frogs), Urodela (the salamanders), and Apoda (the caecilians). However the emerging consensus is that they likely originated from temnospondyls, the most diverse group of prehistoric amphibians, during the Permian period. The origin of modern amphibians belonging to Lissamphibia, which first appeared during the Early Triassic, around 250 million years ago, has long been contentious. They diversified and became dominant during the Carboniferous and Permian periods, but were later displaced by reptiles and other vertebrates. 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. 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. They are superficially similar to reptiles like lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed.
Skeleton system of frog skin#
Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems.
All living amphibians belong to the group Lissamphibia. Īmphibians are four-limbed and ectothermic vertebrates of the class Amphibia. Many amphibians-like this Ceratophrys cranwelli-exhibit biofluorescence.
0 kommentar(er)
