A New Species ofAnagaudryceras(Ammonoidea, gaudryceratidae) From The Lowest Maastrichtian of Hokkaido, Japan

Anagaudryceras compressum sp. nov., the most slender of this genus, is newly described from the Nostoceras hetonaiense Zone of earliest Maastrichtian age (Late Cretaceous), in the Hobetsu area, Hokkaido, northern Japan. Its shell is fairly small (< 80 mm in diameter) and compressed with a highly arched venter. The last whorl is ornamented with low, broad, gently flexed band-like ribs. Its ornamentation is very similar to A. matsumotoi, thus suggesting a close phylogenetic relationship with this taxon, which is probably its descendant.