It is endemic to southern Brazil and is only known from its type locality, Serra da Pedra Branca do Araraquara in Guaratuba, Paraná.

[1][3] The specific name insperatus means "unexpected" or "surprising" in Latin and alludes to the fortuitous finding of a new species among old museum specimens, originally identified as Physalaemus olfersii;[2] taxonomically, it is part of the so-called Physalameus olfersii species group.

The arms are short and slender, and the fingers are very thin and long and with slightly expanded tips.

[2] The species occurs in Atlantic Forest, but there is no specific information on its microhabitat or ecology.

Habitat destruction caused by urban development and land use change (for, e.g., agriculture) is a general threat to Atlantic Forest.