This is a "life model" of Placenticeras meeki. The shell is a cast replica of an original ammonite. Soft body parts were sculpted by Neal L. Larson, Vice President of Black Hills Institute.

Placenticeras are a tightly coiled ammonite found worldwide throughout most of the Late Cretaceous. They are characterized by a flat narrow venter, broad flanks, and a moderately involute umbilicus. Adult forms ranged in size from about 10 cm to more than a meter in diameter.

This specimen was a macroconch, probably a female, based on modern cephalopod gender size relationships. The smaller microconchs were about one forth to one half the size of the macroconchs. From shell isotope studies, it is known that Placenticeras inhabited the upper part of the water column, near the surface of the ocean.

The arms and the head of the Placenticeras were based on living cephalopods and calculated for size, looks, and appearance from the size and shape that would be able to fit in the shell. Stalked eyes were given to the ammonite, because there was room to accommodate them, and some modern octopus have them. The colors chosen for the arms and head are also based on living cephalopods, whose colors change with their moods.