The black-spined Atlantic tree-rat is an arboreal spiny rat of eastern Brazil's Atlantic Forest. It has a reddish-brown back with black streaks, while the underside varies in color.
Its reddish-brown dorsal fur is streaked with black; the underside ranges from buff-white to gray-yellow.
Tree-rats in this genus are arboreal. Records of P. nigrispinus include evergreen broadleaf and semideciduous forest, both along the coast and inland in western São Paulo state.
An extinction-risk assessment has not been added yet.