Tsunyidiscus appeared near the end of the Lower Cambrian, during the late Atdabanian stage of geologic time and some collections suggest it may have survived into the Botomian.

The occipital ring (LO) is at least as long as L1, usually expanded laterally, and may bear a sharp posteriorly directed spine.

The glabella of Tsunyidiscus is extremely similar to that of Dipharus clarki, and distinct from all other eodiscoids.

D. clarki is thought to represent an immature stage of the redlichioid Bulaiaspis rather than an eodiscoid.

This is because of the dominant palpebroocular ridges, extremely long librigenae, and free pleural tips on the pygidium of variable numbers of segments.