Rinetrigonia and Its Allies

In this paper, the writer has re-examined and discussed the classification, the complicated phyletic relationships and the mode of life of the Pterotrigoniinae van HOEPEN, 1929 em. KOBAYASHI and NAKANO, 1957 and described and listed a number of species. Metacanthotrigonia nov. typified by Pterotrigonia (Rinetrigonia) yeharai NAKANO and NUMANO is a new subgenus of Acanthotrigonia van HOEPEN, 1929 and is characterized by, having the discrepant ribbing on the anterior and the posterior part of the flank. It is known in the Aptian to the Turonian of Japan and Manghyschlack.