. Breviora. 1960 AMMONITES FROM IWAI FORMATION, JAPAN The specimen is fragmentary but appears from the illustration to be reasonably placed in Aspenites. Another specimen has been uncovered from the lower fossiliferous bed that is of much better preservation and is without any doubt an indeterminate species of Aspenites. Previous assessments of the age of the Iwai formation rested largely on the identification of the most common species in the lower fauna — Diencroceras iwaiense (Sakagami) -as an Ophi- ceras. Shimizu (1932) appears to have been the first to comment on the Iwai ammonites, thoug
. Breviora. 1960 AMMONITES FROM IWAI FORMATION, JAPAN The specimen is fragmentary but appears from the illustration to be reasonably placed in Aspenites. Another specimen has been uncovered from the lower fossiliferous bed that is of much better preservation and is without any doubt an indeterminate species of Aspenites. Previous assessments of the age of the Iwai formation rested largely on the identification of the most common species in the lower fauna — Diencroceras iwaiense (Sakagami) -as an Ophi- ceras. Shimizu (1932) appears to have been the first to comment on the Iwai ammonites, though Fujimoto (1926) discussed some. Fig-. 1. l)iagi;iiimi;iti(.- representation of i\w suture of (a) Oiccnitcs shimizui (Sakagami), holotype (from Sakagami, 1955, pi. '2, tig. 2c) X 7; (b) Owcnites koeneni Hyatt and Smitli, from a paratype of 15 mm. in diameter (from Hyatt and Smith, 1905, pi. 10, tig. 10), X 8; (e) Diencro- ceras iioaiense (Sakagami), partial suture of holotji^e (from Sakagami, 1955, pi. 1, fig. le), X 10. Pseudomonutis, earlier. Forms like Dieneroceras iwaieMse are extremely difficult to place stratigraphically, and it was not until the presence of such genera as Owenites and Aspe)titcs was estab- lished that both the age and generic assignment of the "Ophi- ceras" could be properly Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. , Museum of Comparative Zoology, Harvard University
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