Henodus was the placodont that had the greatest (albeit wholly superficial) resemblance to a turtle. Like turtles, it had a shell formed from a plastron on the underside and a carapace on top. The carapace extended well beyond the limbs, and was made up of individual plates of bony scutes. The armor was fused to its spine, and its limbs were situated in normal positions, unlike the turtle, where they are located inside the ribcage. The weak limbs of Henodus suggest it spent little time on land.
Henodus chelyops also had two teeth--one on each side of its mouth, though the remaining teeth were replaced by a beak. These teeth were flat to crush bottom dwelling shellfish. The head was squared-off at the front, just ahead of the eyes. Worthy of note is that Henodus is the only placodont thus far found in non-marine deposits, suggesting it may have lived in brackish or freshwater lagoons.
Henodus, though featured far out of its appropriate timespan, is a playable creature in the video game Sea Monsters: A Prehistoric Adventure.