During the Carboniferous and Permian, the number of trilobite genera fell consistently until the extinction of the group at the end of the Palaeozoic. Ditomopyge was one of the last representatives of the family Phillipsiidae. It was comparatively small, with an opisthoparian suture (see cephalic suture), well-developed eyes, and a fused pygidium or tail area. D. scitula is known from the Upper Carboniferous of N. America.