Petalichthyida

Petalichthyida Temporal range: Early Lochkovian - Frasnian
Lunaspis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Placodermi
Order:	†Petalichthyida Jaeckel, 1911
Families
Diandongpetalichthys Quasipetalichthyidae Macropetalichthyidae

Petalichthyida is an extinct order of small, flattened placoderm fish. They are typified by their splayed pectoral fins, exaggerated lateral spines, flattened bodies, 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. The earliest and most primitive known petalichthyid is Diandongpetalichthys, which is from earliest Devonian-aged strata of Yunnan. The presence of Diandongpetalichthys, along with other primitive petalichthyids including Neopetalichthys and Quasipetalichthys, and more advanced petalichthyids, suggest that the order may have arisen in China, possibly during the late Silurian.

Because they had compressed body forms, it is speculated they were bottom-dwellers that chased after or ambushed smaller fish. Their diet is not clear, as none of the fossil specimens found have preserved mouthparts.