UK Ammonite Placenticeras IF-UKA-16-013

Placenticeras intercalare
Pierre Formation
Upper Cretaceous (Campanian)
Meade County, South Dakota 

This example of P. intercalare has well defined features characteristic of the species.  The specimen has a nearly complete body chamber and some sutures are visible.  The ammonite shows sign of injury pathology and makes this specimen of particular interest.  The ammonite is 4.5 inches across.
Placenticeras intercalare is smaller than P. meeki and has a thicker whorl section, narrower flanks and greater ornamentation.  There are two rows of well-defined tubercles on the flanks, one near the umbilicus and the second approximately two-thirds of the distance from the umbilicus toward the ventral edge.  Minor broad, low, rounded ribs seem to connect these tubercles.  The venter is slightly wider than that of P. meeki and has small clavate tubercles on both edges.