Pliocaenicus tanimurae, a new Pliocene diatom species from Aguni Island, Okinawa Prefecture, southwestern Japan

Abstract

Pliocaenicus tanimurae sp. nov., from Early Pliocene sediment of the Fudenzaki Formation, Aguni Island, Okinawa Prefecture, southwestern Japan is described here. The new species is round to elliptical with a slightly tangential undulated valve face. Valve face of the elliptical valves are more elliptical than the valves themselves. Several valve face fultoportulae in the valve center form a circle. Costae alternate thicker (sometimes slightly recessed) and thinner with mantle fultoportulae located on slightly recessed thicker costae. Both valve face and mantle fultoportulae have three satellite pores. Alveoli have centrifugal ‘roofing over’. One rimoportula is located near the edge of the marginal area of the valve face at the base of a costa. The new species is shown in light microscopy and scanning electron microscopy photographs and compared with similar taxa of P. costatus (Loginova, Lupikina & Khursevich) Flower, Ozornina & A.I.Kuzmina, P. seczkinae Stachura-Suchoples, Genkal & Khursevich and P. omarensis (Kuptsova) Stachura-Suchoples & Khursevich.

Keywords:

• Japan
• Okinawa
• Pliocaenicus tanimurae
• Pliocene

Acknowledgements

I wish to thank Kosho Kamiya, a retired high school teacher in Okinawa Prefecture and Kazuhiko Uemura, of the National Museum of Nature and Science, Japan for providing information on the geology of Aguni Island and the sampling sites.