What is "brachydeirus"

Brachydeirus is a genus of small to moderately large-sized arthrodire placoderms from the Late Devonian of Europe, restricted to the Kellwasserkalk Fauna of Bad Wildungen and Adorf.

Species have, in cross section, a highly compressed body, a pointed, sometimes highly elongated snout, and tremendous orbits. The living animals would have superficially resembled modern-day trout or small mackerels. As per the family, the trunk shield is short. The genus is distinguished from other members of the family in that the median dorsal plate of the trunk shield is often keeled, with the keel often very high and prominent.