Bryantolepis brachycephala (Bryant)
Lower Devonian (Seigenian)
Beartooth Butte Formation
Beartooth Butte
Wyoming, USA.

A rare fossil skull of Bryantolepis brachycephala, an early Devonian placoderm from the famous Beartooth Butte Formation of Wyoming. Placoderms were among the earliest jawed vertebrates, representing an important stage in the evolution of armored fishes and the development of modern vertebrate body plans.
32mm skull on 43m slab. Very rare

See: Denison, Robert H. (1962). A reconstruction of the shield of the arthrodire, Bryantolepis brachycephalus (Bryant). Vol. 14. Chicago: Chicago Natural History Museum. (Link to the original paper – opens in new window)