Its not neotenic ... My guess is its morphing, hence it being so thin. many species grow large before they morph, Some even reach full adult size before finally morphing.

Any salamander looks like an axolotl at this age.

Going by location it could be a few things ( the picture is not the most clear)

Copes Giant Salamander
Northwestern Salamander
Tiger Salamander ( some dont have color at this age)