Placoderm
The main source of placoderm fossils is the Old Red Sandstone continent. This, in the Devonian, was a united North America and western Europe and the continental shelf areas around it. Fossils from these strata in Scotland were collected since the 18th century, and Louis Agassiz wrote the first survey of fossil fish. A century later, Eric Stensiö showed that placoderms were genuine jawed fish.