Lonniformia

Lonniformia are a group of tetrapod animals comprising the so-called Long-longs and nevotacums, it is a class in the sense of taxonomy. Lonniformia has proven to be a monophyletic group, so it is a valid class.

Except for the existence of metamorphosis, animals of Lonniformia bear many superficial similarities to reptiles, the egg of Lonniformia animals has a structure similar to amnion called "quasi-amnion"; also, as amniota animals, newborn individuals of most Lonniformia animals can breathe the air directly, therefore earlier biologists see Lonniformia as a subclade of reptiles.

However, animals belonging to the class Lonniformia are not reptiles, as Lonniformia is not in the superclade Amniota, since the cellular origin of quasi-amnion cells in Lonniformia animals are different form the origin of amnion cells in true amniota animals. Because Lonniformia is not in the superclade Amniota, animals of Lonniformia are not related to reptiles, birds, dinosaurs or mammals; rather, Lonniformia is distantly related to amphibians, despite most Lonniformia animals look like reptiles and don't rely on bodies of water to live or reproduce.

Besides, Lonniformia animals don't have ankle bones, but three separate bones instead, like amphibians; also, Lonniformia animals don't have the caecum; moreover, Lonniformia animals possess a strong ability to regenerate lost limbs and organs, and their ability to regenerate lost organs is comparable to salamanders.