This group gathers Amphibians subcategory members belonging to the order Caudata, also called Urodela, the salamanders and newts, tailed amphibians found mostly across the temperate Northern Hemisphere, with a much smaller presence in tropical Central and South America. It spans giant aquatic species such as the Chinese giant salamander and Japanese giant salamander, among the largest living amphibians in the world, the hellbender, a large, flat-bodied North American river species, the axolotl, a Mexican species famous for retaining its larval, gilled form for life under normal conditions, a trait called neoteny, and a great many smaller terrestrial and semi-aquatic salamanders and newts across genera such as Ambystoma, the mole salamanders, and Notophthalmus and Triturus, familiar pond newts of North America and Europe respectively. Most members here can regenerate lost limbs, tails and even parts of internal organs to a degree unmatched by almost any other vertebrate group.