Stethacanthus

Stethacanthus was a shark-like Symmoriid chondrichthyan that lived from 385 to 320 mya, from the Late Devonian to the Early Carboniferous. Its remark is the strange, brush-like protrusion on its dorsal fin, giving it the appearance of an ironing board. This structure only exists in male individuals; females lack this structure entirely. This can be inferred that this structure was used as a sexual display. In Chased by Dinosaurs: Sea Monsters, a Stethacanthus swam for a brief moment in the Devonian seas, and in Walking With Monsters, a Stethacanthus was pursuing a Hynerpeton before being devoured by a Hyneria.