Fig. 6 in Jaws of Late Cretaceous Placenticeratid Ammonites: How Preservation Affects the Interpretation of Morphology

Fig. 6. Lower jaw of Placenticeras meeki Böhm, 1898, or Placenticeras costatum Hyatt, 1903, AMNH 47277, Baculites cuneatus Zone, Bearpaw Shale, Welling, Alberta, Canada, ventral view, anterior end on top. A. Coated. B. Uncoated. Part of the coarsely crystalline black material is missing exposing two radial ridges flanked by grooves (arrows), which are expressed as grooves and ridges, respectively, on the dorsal side, 31.