Isistius trituratus was an extinct relative of modern cookiecutter sharks and possessed one of the most specialised shark dentitions in the London Clay fauna. Its lower teeth formed a close-set cutting blade rather than a series of separate grasping points.

Living cookiecutter sharks use a similar dental arrangement to remove plugs of tissue from much larger animals. The comparable lower dentition of I. trituratus suggests that some form of specialised cutting or ectoparasitic feeding may already have evolved in the lineage, although this behaviour cannot be demonstrated directly from fossil teeth.

The species was a small shark compared with the major lamniform predators around it, but its unusual feeding apparatus would have allowed it to exploit a very different ecological niche. Its fossils therefore provide an early record of extreme feeding specialisation among squaliform sharks.