According to Tarlo (1960), L. pachydeirus differs from L. ferox in the morphology of its teeth and cervical vertebrae. L. pachydeirus has enamel ridges closely packed on inner surface and 6-7 evenly spaced ridges on outer surface, cervical vertebrae with faint ventral keel (Tarlo, 1960).
Holotype specimen of Liopleurodon pachydeirus (from Tarlo, 1960).