The lepospondyls are urodele-like amphibians of the Paleozoic Era, some of which have been considered ancestral or closely related to reptiles or modern amphibians. Their origin is enigmatic, and the earliest occurrences reveal a long-established division into three contrasting orders: the serpentine aistopods, the newt-like nectrideans and the deceptively reptilian microsaurs. The Subclasses Lepospondyli and Labyrinthodontia are not so disparate as to indicate a polyphyletic origin for the Amphibia. Which subclass gave rise to the present-day Lissamphibia is still disputed, but superficial similarities between lepospondyls and lissamphibians cannot mask the fundamental discrepancies in temporal range and morphology and (apparently) in life history as well.