Petalichthyida

From Paleos

The Petalichthyida was an order of small, flattened placoderm fish. They were typified by their splayed fins, and numerous tubercles that decorated all of the plates and scales of their armor. They reached a peak in diversity during the Early Devonian and were found throughout the world, particularly in Europe (especially in Germany), North America, Asia, South America, and Australia. The petalichthids Lunaspis and Wijdeaspis are among the best known. There was an independant diversification event that occured in what is now Southern China, producing a handful of unique genera that were once placed in their own order, "Quasipetalichthyida," named after the first discovered (and described) species there, Quasipetalichthys haikouensis. Soon after the Petalichthids' diversification, they went into a decline, until the last few species were exterminated along with the rest of the placoderms during the Late Devonian extinction event.

From what can be garnered from their compressed body forms, it is presumed that the Petalichthyids were bottom-dwellers that either chased after, swam after, or ambushed smaller fish. However, their diet is highly speculatory, as none of the fossil specimens found have the mouth or mouth parts preserved.