Mytiloides hattini n. sp.: a guide fossil for the base of the Turonian in the Western Interior of North America

Mytiloides hattini, a new species of inoceramid bivalve from the basal Turonian (Upper Cretaceous), is described and its stratigraphic importance discussed. This inoceramid is particularly significant because its first occurrence can be used as a marker for the base of the Turonian in strata that typically contain no ammonites and few other taxa. The lowest occurrence of Mytiloides hattini is characterized by abundant specimens over wide regions of the Western Interior of North America; this species also apparently occurs in the lowest Turonian strata of western Europe. The typical absence of ammonites in this stratigraphic interval potentially makes the first occurrence of Mytiloides hattini an important fossil for regional and intercontinental correlation of the Cenomanian-Turonian boundary.