Truncatulus gen. nov., a new fossil resting spore morphogenus related to the marine diatom genus Chaetoceros (Bacillariophyceae)

Abstract

I. Suto. 2006. Truncatulus gen. nov., a new fossil resting spore morphogenus related to the marine diatom genus Chaetoceros (Bacillariophyceae). Phycologia 45: 585–601. DOI: 10.2216/04-91.1

A new fossil marine diatom resting spore morphogenus (form genus) Truncatulus I. Suto gen. nov. is described using samples from DSDP Site 338 in the Norwegian Sea, Sites 436 and 438 in the northwest Pacific Ocean and from the onland Newport Beach Section, California. Truncatulus is characterized by the circular, elliptical or polygonal flat plate on the truncated elevation of the oval to elliptic epivalve or/and hypovalve, and includes seven new species (T. simplex, T. atlanticus, T. ellipticus, T. norvegicus, T. californicus and T. hajosiae), and one new combination, T. tortonicus (Hajós) I. Suto. Truncatulus appeared in the early Oligocene and became extinct in the late Pliocene. The oldest species, T. ellipticus, arose in the early Oligocene. Truncatulus norvegicus, T. ellipticus, T. atlanticus and T. hajosiae might be endemic species in the Norwegian Sea, and the first and last occurrences of T. norvegicus and the first occurrences of T. ellipticus, T. atlanticus and T. hajosiae may be useful for North Atlantic diatom biostratigraphy. Truncatulus californicus is endemic in the northeastern Pacific and restricted to a relatively short interval in middle Miocene Zone NPD 5B; it is therefore an excellent stratigraphic marker for this horizon. The last and cosmopolitan species T. tortonicus became extinct in the late Pliocene in the northwestern Pacific.

Key Words::

• Diatoms
• Chaetoceros
• Fossil
• Resting spore
• Neogene
• ODP
• Stratigraphy
• Taxonomy
• Truncatulus

ACKNOWLEDGMENTS

I am especially grateful to Yukio Yanagisawa (Geological Survey of Japan/AIST), who provided numerous helpful suggestions and reviewed the manuscript carefully. I also thank Fumio Akiba (Diatom Minilab Akiba Ltd.) for invaluable discussions and his careful review of the manuscript; John A. Barron (U.S. Geological Survey) for his permission to study the Newport Beach samples and his detail review; Karin G. Jensen to her careful review and comments; Yoshihiro Tanimura (National Science Museum, Tokyo), who kindly curated the holotype specimens described in this paper; and Kenshiro Ogasawara (University of Tsukuba) and my colleagues for their helpful advice and encouragement. This research used samples provided by the Ocean Drilling Program (ODP). ODP is sponsored by the U.S. National Science Foundation (NSF) and participating countries under management of the Joint Oceanographic Institution (JOI).