See text Pleuracanthus Agassiz 1837 Xenacanthus (from Ancient Greek ξένος, xénos, 'foreign, alien' + ἄκανθος, akanthos, 'spine') is an extinct genus of xenacanth cartilaginous fish.

This arrangement resembles that of modern conger eels, and Xenacanthus probably swam in a similar manner.

A distinctive spine projected from the back of the head and gave the genus its name.

The spike has even been speculated to have been venomous, perhaps in a similar manner to a sting ray.

The teeth had an unusual "V" shape, and it probably fed on small crustaceans and heavily scaled palaeoniscid fishes.