The species was previously placed in the genera Gonionotophis, Mehelya, and Simocephalus.

[3] G. nyassae is found in Botswana, Burundi, Democratic Republic of the Congo, Eswatini, Kenya, Malawi, Mozambique, Namibia, Rwanda, Somalia, South Africa, Tanzania, Zambia, and Zimbabwe.

The female may attain a snout-to-vent length (SVL) of 52 cm (20 in).

Unlike the Common File snake, this snake lacks the light dorsal stripe but has the characteristic triangular body,[4] Ventrally it is black to dark olive (uniform phase), or cream-olive to white (bicolored phase).

[5] The black file snake is oviparous.