Cryptobranchoidea

The Cryptobranchoidea are a suborder of salamanders found in Asia, European Russia, and the United States. They are known as primitive salamanders, in contrast to Salamandroidea, the advanced salamanders.^[1] It has two living subdivisions, Cryptobranchidae (Asian giant salamanders and hellbenders), and Hynobiidae, commonly known as Asian salamanders.

Cryptobranchoidea Temporal range: Middle Jurassic - Present Bathonian–Present PreꞒ Ꞓ O S D C P T J K Pg N
Cryptobranchus alleganiensis
Hynobius fossigenus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Amphibia
Order:	Urodela
Suborder:	Cryptobranchoidea Dunn, 1922
Subgroups
†Chunerpeton? †Jeholotriton †Pangerpeton †Nesovtriton? †Iridotriton? †Kiyatriton? †Laccotriton †Sinerpeton Cryptobranchidae Panhynobia Ji, Anderson & Gao, 2021 †Liaoxitriton †Linglongtriton †Neimengtriton †Regalerpeton †Nuominerpeton Hynobiidae

Giant salamanders are obligate paedomorphs with partial metamorphosis,^[2] but Asiatic salamander goes through a full metamorphosis. The only known exceptions are the Longdong stream salamander, which has been documented as facultatively neotenic, and the Ezo salamander, where a now assumed extinct population from Lake Kuttarush in Hokkaido had neotenic traits like gills in adults.^[3]

The oldest members of the group are known from the Middle Jurassic (Bathonian) aged Yanliao Biota of China.^[4]

Taxonomy

This suborder contains only two families at present. All other members are extinct and are only known as fossils.

• †Chunerpeton Haifanggou Formation, China, Middle Jurassic (Bathonian) (neotenic, has alternatively been recovered outside of Cryptobranchoidea)^[5]
• †Jeholotriton Haifanggou Formation, China, Middle Jurassic (Bathonian) (neotenic)
• †Pangerpeton Haifanggou Formation, China, Middle Jurassic (Bathonian)
• †Nesovtriton Bissekty Formation, Uzbekistan, Late Cretaceous (Turonian)
• †Iridotriton Morrison Formation, United States, Late Jurassic (Tithonian)
• †Kiyatriton Itat Formation, Russia, Middle Jurassic (Bathonian) Ilek Formation, Russia, Early Cretaceous (Barremian-Aptian) (Presumed to be a cryptobranchoid)
• †Laccotriton Fengshan fossil bed, China, Late Jurassic (Tithonian)
• †Sinerpeton Fengshan fossil bed, China, Late Jurassic (Tithonian)
• Cryptobranchidae (Late Cretaceous-Recent)
• Panhynobia^[4]
  • †Liaoxitriton Jiufotang Formation, China, Early Cretaceous (Aptian)
  • †Linglongtriton Tiaojishan Formation, China, Late Jurassic (Oxfordian)
  • †Neimengtriton Haifanggou Formation, China, Middle Jurassic (Bathonian)
  • †Regalerpeton Dabeigou Formation, China, Early Cretaceous (Hauterivian)
  • †Nuominerpeton Longjiang Formation, China, Early Cretaceous (Aptian)
  • Hynobiidae (Miocene-Recent)