Psephophorus polygonus is the type species, and was discovered by von Meyer in 1846.
Fossils of the species have shown bony, carapacial ridges, adjacent, small and polygonal bony ossicles which measure about 22 × 25 mm.
When the ossicles extend further along the longitudinal axis, their size increases up to an average of 33 × 41 mm.

Psephophorus calvertensis was first named by Palmer in 1909.
It was so named for being found in the Calvert Formation.
P. calvertensis is a rarely found specimen.

Psephophorus eocaenus was first named by Andrews in 1901.

Psephophorus californiensis was first named by Gilmore in 1937.

Psephophorus terrypratchetti was discovered in the 1990s by Richard Köhler in New Zealand and named in 1995 after the author Terry Pratchett, who wrote a series of fantasy books set on a world carried on the back of a giant turtle.
Psephophorus polygonus is the type species, and was discovered by von Meyer in 1846. Fossils of the species have shown bony, carapacial ridges, adjacent, small and polygonal bony ossicles which measure about 22 × 25 mm. When the ossicles extend further along the longitudinal axis, their size increases up to an average of 33 × 41 mm.
Psephophorus calvertensis was first named by Palmer in 1909. It was so named for being found in the Calvert Formation. P. calvertensis is a rarely found specimen.
Psephophorus eocaenus was first named by Andrews in 1901.
Psephophorus californiensis was first named by Gilmore in 1937.
Psephophorus terrypratchetti was discovered in the 1990s by Richard Köhler in New Zealand and named in 1995 after the author Terry Pratchett, who wrote a series of fantasy books set on a world carried on the back of a giant turtle.
Psephophorus