A New Species of Hoplopteryx from the Carlile Formation (cretaceous) of South Dakota

A species of the beryciform fish genus Hoplopteryx, collected from rocks of Turonian Age in the Pool Creek Member of the Carlile Shale Formation, is described from the fossil record of South Dakota for the first time. The specimens are part of the Bishop Collection, now housed in the repository at the South Dakota School of Mines and Technology (SDSM). Despite their geographic distance from the core of Hoplopteryx distribution, the South Dakota specimens lie within the first half of the known geologic range of the genus. They are distinctive in that they occur at a very high paleolatitude compared to all other known specimens of Hoplopteryx. They differ anatomically from all previously described species, particularly the type species Hoplopteryx antiquus. They are consistently small. They are also distinct in the crests and depressions of the skull. The absence of a walled mucus cavity on the frontals and the ornamentation of cranial bones are particularly distinctive in the South Dakota hoplopterids. We herein describe them as a new species, Hoplopteryx dakotaensis.