Jaw apparatuses of Late Cretaceous ammonites donated to the Kitakyushu Museum of Natural History

Abstract

Two specimens of ammonite jaws from the Late Cretaceous deposits in northwestern Hokkaido have been donated to the Museum by Mr. Hiroji Kokubu. As a result of the examination, they are upper jaws of Gaudryceras sp. embedded in Lower Santonian deposits of the Obira area. Restored height of the gaudryceratid body chamber might be 50 to 60 mm judging from the ratio of the jaw height or wing length to the height of body chamber.