The Rostroconchia is a class of extinct molluscs dating from the early Cambrian to the Late Permian.

Rostroconchs began their life as a small, bilaterally symmetrical, univalved protoconch planktonic larva.

The two valves would have been rigidly fixed in place, and would have to have been broken periodically to allow the rostroconch shell to grow.

Heraultipegma is the earliest, very primitive, rostroconch genus dating from the Late Terreneuvian.

In Conocardium, a more advanced rostroconch, the outer shell layers do not cross the entire margin, suggesting independent steps towards the bivalve flexible hinge.