Key to species of Costulodonta gen. nov.

1 Parietal dentition absent ............................................................................... C. bidens gen. et sp. nov.

– Parietal dentition present ................................................................................................................... 2

2 Parietal region with a single low, in-running ridge ....................... C. trilamellaris gen. et comb. nov.

– Parietal region with two lamellae or one lamella plus an in-running row of denticles ..................... 3

3 Palatal region lacking dentition; baso-columellar region with a single, low denticle ......................... .............................................................................................................. C. burnupi gen. et comb. nov.

– Palatal region dentate; baso-columellar denticle also present .......................................................... 4

4 Palatal region with 3–4 denticles; upper parietal tooth an in-running lamella .................................... ................................................................................................................. C. pluridens gen. et sp. nov.

– Palatal region with two broad, deep-set in-running ridges; upper parietal comprising an in-running row of two or more denticles .............................................................. C. acinaces gen. et comb. nov.