A new species of Enchodus from the Western Interior Seaway of North America and a taxonomic revision of Enchodus dirus , Leidy, 1857

Enchodus is a diverse and widespread genus of teleost fish known from the Late Cretaceous. Many North American species of Enchodus were erected based on isolated remains, including Enchodus dirus Leidy, 1857, which is named for a fragmentary dentary. We redescribe this holotype and find it to be nondiagnostic, lacking any defining characters to separate it from other species of Enchodus. A complete skull from the Niobrara Chalk, which was previously referred to E. dirus, is designated as the holotype of a new taxon, Enchodus machairus sp. nov. Enchodus machairus has a unique character suite, including: sigmoidal palatine teeth lacking postapical barbs, palatine teeth with a symmetrical cross-section and a single cutting edge, no marginal row of teeth on the mandible, no ornamentation on the mandible, and a rostrodermethmoid that is wider than long with lateral wings. The dentary teeth of the holotype of E. machairus lack prominent posterior ridges, unlike the holotype of E. dirus, and the two specimens are stratigraphically separated by 10 million years. Previous specimens referred to E. dirus are reviewed, and two additional specimens from the Niobrara Formation are referred to Enchodus machairus. Some Enchodus specimens from the Fox Hills Formation, including the holotype of E. dirus, may be better referred to Enchodus gladiolus, although none are complete enough to be certain. A nearly complete skull from Greece, which was previously identified as E. cf. E. dirus, is not conspecific with E. machairus.