 In the following years, the genus grew to include thirteen species.Many of these species were erected on the basis of differences in the teeth and the positioning of the frontal and parietal bones.A 2008 study narrowed "Emydops" down to two species, "E. arctatus" (first described by English paleontologist Richard Owen as "Kistecephalus arctatus" in 1876) and the newly described "E. oweni".