Iniopteryx was a small, peculiar holocephalan that lived during the Carboniferous period, around 300 million years ago, in the shallow seas of what is now North America. Its name means "narrow wing", a reference to its most striking feature: enormous, wing-like pectoral fins that pointed backwards over its body, unlike any fish alive today. With its large eyes set close together and a whip-like tail, Iniopteryx likely swam in a distinctive flapping motion, gliding through the water like a tiny underwater bird. It was one of the many bizarre cartilaginous fish, relatives of the chimaeras, that thrived in the tropical seas of the Paleozoic.