Lepospondyli

Lepospondyli are a group of small but diverse Carboniferous to early Permian tetrapods. Six different groups are known, the Acherontiscidae, Adelospondyli, Aïstopoda, Lysorophia, Microsauria and Nectridea, and between them they include newt-like, eel- or snake-like, and lizard-like forms, along with species that do not fit any current category. Various species were aquatic, semi-aquatic, or terrestrial. None were large (the biggest genus, the diplocaulid Diplocaulus, reached a meter in length, but most were much smaller), and it can be assumed that they lived in specialised ecological niches not taken by their more numerous Temnospondyl contemporaries.

Read more about Lepospondyli:  Classification