Didymoceras nebrascense was an extinct species of heteromorph ammonite from the upper Campanian age (around 83 to 70 million years ago).

The initial growth stage produces two more or less straight sections connected with each other by a sharply bent elbow.

Ornamentation of Didymoceras nebrascense consists of a double row of nodes running along the ventral side.

[2] Didymoceras nebrascense was originally described (tentatively) in 1856 as Ancyloceras nebrascensis by the paleontologists Fielding B. Meek and Ferdinand V. Hayden.

Kennedy et al. (2000) placed it under the genus Didymoceras,[2] which in turn is classified under the family Nostoceratidae under the diverse suborder of heteromorph ammonites, Ancyloceratina.

[1] Didymoceras nebrascense occurs in the western edge of what was once an ancient sea that stretched from northern New Mexico to northeastern Montana in the upper Campanian age (around 83 to 70 million years ago) of the late Cretaceous.