Sato T., Tsujino Y., Ishida K., Kozai T., Hachiya K. Newly collected Late Jurassic ammonites from Kurisaka, Tokushima Prefecture, Japan // Bull. Tokushima Pref. Mus. 2008. No.18. P.1-20. pdf: http://www.museum.tokushima-ec.ed.jp/kiyo/2008/Sato%20et%20al.%20 (2008).pdf
New Upper Jurassic ammonites were collected from the Kurisaka Formation in Tokushima Prefecture, Japan. They are Neochetoceras, Lytogyroceras, Simoceras, Orthosphinctes (Ardescia) in addition to already known Ataxioceras (Ataxioceras), all from a single horizon. The age of these assemblages is controversial; first three genera indicate lower Tithonian, whereas the last genus Kimmeridgian (in Tethyan sense). Because no evidence of reworking of the latter sub-assemblage is revealed by detailed stratigraphical survey, the age of the bed can not be assigned to specific horizon within the Kimmeridgian to Tithonian time interval at this moment. Further sedimentological and taphonomical studies are needed for precise interpretation. New species of Neochetoceras (N. ) mizunoi has been described.
P.S. In my opinion, both Ataxioceras and Orthosphinctes (which are really Lower Kimmeridgian taxa) should be re-interpreted as belonging to Tithonian genera, Sublithacoceras and ?Subplanites, respectively, and true age of assemblage described herein is Lower Tithonian
