UK Ammonite Hoploscaphites
Hoploscaphites plenus
Bear Paw Formation
Upper Cretaceous (Maastrichtian)
Dawson County, Montana
The largest scaphite in this specimen is a macroconch form of H. plenus prepared in the original limestone concretion matrix. Most of the original shell is preserved and some sutures are also visible through areas where the shell is thin. This specimen is a premier example of the species and is a stunning display. There is no repair or restoration. Also present in the concretion are partial microconch forms of the species. The specimen comes with the counter-part section of the concretion that contains the impressions of the scaphites.
Hoploscaphites plenus is a robust species characterized by its steep umbilical wall, well-rounded venter and flanks, and large size. This species has fairly straight, medium to fine ribs that tend to bifurcate about two-thirds of the way out on the flanks. It also has small tubercles on the ventrolateral shoulder quite early on the phragmocone that continue almost all of the way to the aperture. There is an inner row of small lateral nodes or bullae above the umbilical shoulder that begin early on the phragmocone, but fade away on the body chamber. Occasionally, a third row of small tubercles is located midflank on the body chamber. The species is characteristic of the Baculites eliasi and Baculites baculus Range Zone.