The Cryptobranchidae are a family of fully aquatic salamanders commonly known as the giant salamanders. They include the largest living amphibians. The family is native to China, Japan, and the eastern United States. They constitute one of two living families within the Cryptobranchoidea, one of two main divisions of living salamanders, the other being the Asiatic salamanders belonging to the family Hynobiidae. The largest species are in the genus Andrias, native to east Asia. The South China giant salamander (Andrias sligoi), can reach a length of . The Japanese giant salamander (Andrias japonicus) reaches up to in length, feeds at night on fish and crustaceans, and has been known to live for more than 50 years in captivity. The hellbender (Cryptobranchus alleganiensis) inhabits the eastern United States and is the only member of the genus Cryptobranchus. Taxonomy The family name is from the Ancient Greek krypto ("hidden"), and branch ("gill"), which refer to how the members absorb oxygen through capillaries of their side-frills, which function as gills. Clade Pancryptobrancha (Cryptobranchidae + Ukrainurus) Genus †Ukrainurus Ukraine, Miocene †Ukrainurus hypsognathus Genus †Chunerpeton? China, Middle Jurassic †Chunerpeton tianyiensis Family Cryptobranchidae Genus Cryptobranchus (hellbenders) †Cryptobranchus saskatchewanensis? Ravenscrag Formation, Canada, Paleocene Cryptobranchus alleganiensis (hellbender) Genus Andrias (Asian giant salamanders; sometimes classified among the Cryptobranchus) Andrias davidianus (Chinese giant salamander) – (Simplified Chinese: ; pinyin: ) (may actually be a species complex of 5 different species) Andrias sligoi (South China giant salamander) Andrias japonicus (Japanese giant salamander) – () Andrias jiangxiensis (Jiangxi giant salamander) †Andrias matthewi North America, Miocene †Andrias scheuchzeri Europe, Oligocene-Pliocene Genus †Eoscapherpeton Central Asia, Late Cretaceous (Cenomanian-Campanian) Genus †Aviturus Mongolia, Paleocene †Aviturus exsecratus Genus †Ulanurus Mongolia, Paleocene †Ulanurus fractus Genus †Zaissanurus Kazakhstan, Oligocene †Zaissanurus beliajevae Fossil record Extant species in the family Cryptobranchidae are the modern-day members of a lineage that extends back tens millions of years. The oldest known fossils of cryptobranchoids are known from the Middle Jurassic of China. Chunerpeton from the Middle Jurassic of China has been suggested to represent the oldest known cryptobranchid. However, some studies have found it to be a more basal cryptobranchoid not more closely related to Cryptobranchidae than to Hynobiidae. The next oldest cryptobranchid is Eoscapherpeton, known from numerous Late Cretaceous deposits in Central Asia, which is suggested to represent a stem-group to modern cryptobranchids. Modern crown group representatives appear during the Paleocene. As the fossil record for the Cryptobranchidae shows an Asian origin for