[1] Like some other species of the genus Mastophora, adult females resemble bird droppings.

Mastophora species, including M. extraordinaria, are "bolas spiders" – adult females capture their prey by using a sticky drop on the end of a single line which they swing at the target, usually a male moth attracted by the release of an analogue of the attractant sex pheromone produced by the female moth.

The carapace was dark brown with a narrow white rim and had low tubercules.

The combined length of the patella and tibia of the first leg was a little more than the width of the carapace at 5 mm (3⁄16 in).

[4] The genus has been placed in the broadly defined subfamily Cyrtarachninae,[5] and within this in the informal group of mastophorines which includes the bolas spiders.