Henodus was a cyamodontid from what is now. It during the late Triassic, being one of the last placodontoids.
We can imagine Henodus like some kind of reptilian ray, paddling it broad flat body across the bed of a shallow lagoon, foraging in the rippled sand with its broad mouth. Its plate-like body would have made it better adapted to searching along flat sea beds than to the shellfish-encrusted reefs frequented by its relatives. Its weak limbs suggest that it did not spend much time on land.
There is a carapace over the whole of the body that stretches out well beyond the span of its limbs, and as in the other cyamodonts this is matched by a plastron, a lower shell, which covers the undersurface. Both carapace and plastron are made up of a geometric array of individual plates. The head is squared off at the front and is shortened in front of the eyes.