Wikipedia
Stenosteus
Stenosteus is a genus of medium-sized selenosteid arthrodire placoderms known from the Upper Famennian Cleveland Shales of Ohio. Estimated skull lengths range from 6 to 9 centimeters
Most fossils of Stenosteus have been scraps of armor and portions of tooth-plates suggestive of Selenosteus. In 1996, enough material of a new species, S. angustopectus, was recovered to allow a reconstruction of armor that resembles that of Selenosteus.