What is "heteroceras"

Heteroceras is a Lower Cretaceous heteromorph ammonite belonging to the ancyloceratacian family, Heteroceratidae, characterized by a helically coiled juvenile shell at the apex followed by slightly curved adult shaft, with a J-shaped section at the end of it. The shell is ribbed; ribs are concave and oblique on the helix, straight and transverse on the later stages.

Heteroceras has been found in France, central Europe, the Caucasus, and Peru. Related genera are Hemibaculites and Cochidites. The family, Heteroceratidae, is a derivative of the Ancyloceratidae.