With a total length that usually falls between 80 and 100mm,
this is the smallest of the Euproctus species. The head is
longer than broad, flattened and with a rounded snout. The tail
is low and oval in cross section. The tail is longer than the
snout-vent length in males, shorter in females. Parotoid glands
are clearly distinguishable. The skin is granular in the
terrestrial phase, and smooth in the aquatic phase. Color is
highly variable. The dorsal side is usually a dark brown, but
dark green, golden yellow, bronze, bright green marmorated and
silver gray patterns also occur, together with highly variable
spot patterns. A yellow to orange middorsal line is usually
brighter in juveniles and subadults. A middorsal furrow is
usually clearest on the back of the head. There is a clear
sexual dimorphism in E. montanus. Males possess spurs on the
thighs of the hind legs. The cloaca in males resembles a conical
protuberance that projects backward and contains a pseudopenis
that probably facilitates the direct tran