Rees and Underwood (2008) erected Planohybodus for Meristodonoides-like teeth that tended to be larger, had a flatter labial crown face, a wider and more compressed cusp, better developed cutting edge, higher shoulders often bearing multiple slender cusplets, and a root with a "well-excavated" basal face.
The type, Planohybodus peterboroughensis Rees and Underwood 2008, was from the Middle Jurassic of England; the distribution was listed as Middle (possibly Early) Jurassic to Early Cretaceous (Berriasian–Barremian) of Western Europe.

Bourdon et al (2011) reported as Planohybodus sp. three teeth from the Pt. Lookout Fm. (Santonian) of New Mexico. These teeth differed from the other reported taxa (Meristodonoides and ?Egertonodus) by their size, multiple cusplets and high shoulders. There were two forms of teeth incorporated as such, one with multiple slender cusplets and the other with a single broadly expanded cusplet; interpreted as individual, positional and/or ontogenetic variations of a single species.

Selected References

Bourdon, J., Wright, K., Lucas, S.G., Spielmann, J.A. and Pence, R., 2011. Selachians from the Upper Cretaceous (Santonian) Hosta Tongue of the Point Lookout Sandstone, central New Mexico. New Mex. Mus. Nat. His. and Sc., Bulletin 52; 54pp.
Rees, J. and Underwood, C., 2008. Hybodont sharks from the English Bathonian and Callovian (Middle Jurassic): Palaeontology, v. 51, p. 117-147.