Lehmanosteus
Lehmanosteus is an extinct monospecific genus of arthrodire placoderm fish, named after French paleontologist Jean-Pierre Lehman. The type species Lehmanosteus hyperboreus was described in 1984, and was found in Early Devonian strata of the Wood [Bay Formation] on the island of Spitsbergen, Svalbard in Norway.
It is one of the more basal members of the order Arthrodira, as shown in the cladogram below: