A fossil freshwater Thalassiosira, T. inlandica sp. nov. (Bacillariophyta), with semicontinuous cribra and elongated marginal fultoportulae

Abstract

T. Hayashi, Y. Tanimura and H. Sakai. 2007. A fossil freshwater Thalassiosira, T. inlandica sp. nov. (Bacillariophyta), with semicontinuous cribra and elongated marginal fultoportulae. Phycologia 46: 353–362. DOI: 10.2216/06-60.1

A fossil freshwater diatom species, Thalassiosira inlandica sp. nov., is described from Pleistocene lacustrine sediments of the Kathmandu Basin on the southern slope of the Nepal Himalaya. Thalassiosira inlandica is characterized by (1) a nonplicated (flat) valve face, (2) networks of ribs and costae, (3) semicontinuous cribra composed of the aggregate of many pore rows, (4) absence of valve face fultoportula, (5) elongated marginal fultoportulae, and (6) multiple rimoportulae in the mantle area. This new species is compared with allied taxa based on several morphological characters.

Key Words::

• Elongated fultoportula
• Fossil
• Initial valve
• Nepal Himalaya
• New species
• Pleistocene
• Semicontinuous cribra
• Thalassiosira inlandica

ACKNOWLEDGMENTS

We would like to thank Dr Mark B. Edlund, Associate Editor of Phycologia; Dr Matthew L. Julius; and an anonymous reviewer. Their constructive and helpful reviews improved the quality of the study. We would also like to thank Dr B.N. Upreti and the Department of Geology, Tribhuvan University, for their kind help in the course of drilling. This study was supported by the Grant-in-Aid for Scientific Research (A)(No. 11304030) and (B)(No. 14340152) from the Japan Society for Promotion of Science to H. Sakai, and Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists to T. Hayashi.