FIGURE 9 in LARGE SCAPHITID AMMONITES (HOPLOSCAPHITES) FROM THE UPPER CRETACEOUS (UPPER CAMPANIAN–LOWER MAASTRICHTIAN) OF NORTH AMERICA: ENDLESS VARIATION ON A SINGLE THEME

FIGURE 9. Jaws of Hoploscaphites, AMNH loc. 3921, lower Baculites baculus Zone, Pierre Shale, Cedar Creek Anticline, east-central Montana. A–F. Species closely related to Hoploscaphites crassus (Coryell and Salmon, 1934), microconch, AMNH 80109, with associated lower jaw (D-F). A. Right lateral; B. apertural; C. ventral, showing growth deformity manifested as a furrow along the midventer. D. Impression of the lower jaw. E. Left wing of the lower jaw. F. Right wing of the lower jaw. G. Tip of an upper jaw attributed to Hoploscaphites, dorsal view, AMNH 63600. H, I. Lower jaw attributed to H. crassus, AMNH 64498. H. Right lateral view, with hole. I. Close-up of hole. J. SEM of a lower jaw attributed to Hoploscaphites, AMNH 64512. The lower jaw consists of an inner black layer (left) originally composed of chitin, and a mineralized outer layer called the aptychus (right), originally composed of calcite.