Placoderms Temporal range: Mid Silurian – Upper Devonian 430–365 mya
Dunkleosteus skull
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Infraphylum:	Gnathostomata
Class:	†Placodermi McCoy, 1848

Lunaspis, one of the small early Petalichthyids, from Lower Devonian shales

The placoderms (Placodermi: Greek = plated skin) were a class of armoured prehistoric fish, which lived from the mid Silurian to the end of the Devonian period. Their head and thorax were covered by armoured plates; the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish, the Gnathostomata. A 380 million year old fossil of one species is the oldest-known example of live birth.

The placoderms were hugely successful in the Devonian period, which is sometimes called the 'Age of Fish'. In the Upper Devonian, a series of extinction events devastated the marine fauna. As the placoderms were predators, this caused a swift decline in their numbers, and the class was entirely extinct by the end of the Devonian.