Cyclotella iwatensis sp. nov. from Mio-Pliocene freshwater sediment, Iwate Prefecture, Japan

Abstract

A new Cyclotella species, C. iwatensis is described from freshwater sediment of the Mio-Pliocene Masuzawa Formation, Shizukuishi Town, Iwate Prefecture, Japan. The new species is characterized by a round central area of the valve face with a radial colliculation and a jagged boundary, marginal striae of different lengths, interstriae often branched, mantle fultoportulae with three satellite pores and one rimoportula located on a costa. The new species is compared with seven similar Cyclotella taxa as well as C. kohsakaensis Tanaka & Kobayasi, a species endemic to Japan.

Keywords:

• fossil
• freshwater diatom
• Mio-Pliocene
• Masuzawa Formation
• Japan
• Cyclotella iwatensis

Acknowledgements

We would like to thank K. Uemura from the National Museum of Nature and Sciences, Tokyo and M. Oishi of the highly professional staff of the Iwate Prefectural Museum for their assistance both with the geological data of the sampling area and at the sampling site itself.