According to Dr. William Cobban of the U.S.G.S., this belongs to an undescribed species of Hoploscaphites. Scaphitid ammonites are dimorphic at maturity. The two forms are called macroconchs and microconchs, which probably correspond to females and males respectively. This one is a macroconch, as distinguished by the nearly straight umbilical shoulder. The length is 5 cm. Here is an example of a microconch.
Back to Itano family home page