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 Argentina, Colombia (La Guajira), the Czech Republic, France, Italy, Japan, Madagascar, Serbia and Montenegro, South Africa, Spain, USSR and the United States (Kansas, Wyoming). Related genera are "Hemibaculites" and "Cochidites". The family, Heteroceratidae, is a derivative of the Ancyloceratidae.