ALVEUS, GEN-NOV (BACILLARIACEAE, BACILLARIOPHYTA), A HEAVILY SILICIFIED DIATOM FOUND IN WARM WATER OCEANS

Scanning electron microscope images of complete and damaged frustules of Nitzschia marina Grun. revealed an unusual chambered structure of t he valve. This structure is not present in any existing nitzschioid ge nus and warrants an independent generic status for this taxon, which i s therefore separated into Alveus gen. nov. Generic and emended specif ic definitions are provided and presented in the context of their rela tionship to other genera within the family Bacillariaceae. Deep relief of the inner surface of Alveus valves is similar to that of genera Fr agilariopsis, Denticulopsis, Neodenticula, and Crucidenticula. It diff ers from all these diatoms in the alveolar striation. This heavily sil icified diatom was found in samples from the US Joint Global Oceanogra phic Flux Studies cruise TT007 stations 2 and 4, (9 degrees and 5 degr ees N respectively, 140 degrees W) in the equatorial Pacific. Presentl y, this uncommon species is restricted to warm waters. It is very comm on in the surface sediments of the equatorial Pacific and Indian Ocean and in the tropical and subtropical Atlantic. The sedimentary record of Alveus marinus goes back to the Middle Late Miocene (approximately 8 Ma years). (C) 1996 Wiley-Liss, Inc.