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