''Selenosteus brevis'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

large selenosteid

arthrodire Arthrodira (Greek for "jointed neck") is an Order (biology), order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetratin ...

placoderm known from the

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used b ...

Cleveland Shale The Cleveland Shale, also referred to as the Cleveland Member, is a shale geologic formation in the eastern United States. Identification and name The Cleveland Shale was identified in 1870 and named for the city of Cleveland, Ohio. John Stro ...

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

. Scrappy remains from the

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during th ...

Rhinestreet Shales of Erie County,

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

, were attributed by Hussakof and Bryant to this genus in 1919, but, this identification is doubtful. A second species, ''S. kepleri'', was described in 1901, but, not enough differences can be seen between its specimens, and those of the type species to warrant new species status. According to its generally scrappy fossils, ''S. brevis'' had a wide skull with tremendous orbits. And as typical for selenosteids, ''S. brevis'' had weak gnathal plates. The median dorsal plate is crescent-shaped, and has a keel. The average length of the skull is about 16 centimetres from the tip of the rostrum to the posterior border of the

nuchal The nape is the back of the neck. In technical anatomical/medical terminology, the nape is also called the nucha (from the Medieval Latin rendering of the Arabic , "spinal marrow"). The corresponding adjective is ''nuchal'', as in the term ''nu ...

plate.

References

Selenosteidae Placoderms of North America Fossil taxa described in 1896 Paleontology in New York (state) Famennian life Famennian genus extinctions {{Placoderm-stub