TAXONOMY OF THE FOSSIL MARINE DIATOM RESTING SPORE GENUS GONIOTHECIUM EHRENBERG AND ITS ALLIED SPECIES

Abstract

Taxonomic notes are provided on the genus Goniothecium and its allied groups from Arctic core materials, in addition to a synonymy list, microscope observations and several key references for each species. Moreover, the type material of Goniothecium from the Ehrenberg Collection (no. 1651a and 1651b) in the Museum für Naturkunde, Humboldt Universität, Berlin, was obtained in order to examine the structure of G. rogersii. The extinct genus is characterized by a subrectangular frustule and forming paired frustules connected by two epivalves, which possess interlocking linking spines. The genus presently includes 3 species: G. rogersii Ehrenberg, G. danicum Grunow and G. decoratum Bran. A fourth species, Goniothecium loricatum Fenner is here transferred to Hemiaulus loricatus (Fenner in Schrader et Fenner) Suto comb, nov., based on the valve similarity of genus Hemiaulus. Goniothecium has a long stratigraphic history from the Cretaceous to the Pliocene. Goniothecium rogersii and G. decoratum appeared in the Southern Hemisphere in the late Cretaceous and in the middle Eocene, respectively. From the Oligocene, they spread to the Northern Hemisphere. On the other hand, G. danicum appeared in the North Atlantic and/or Arctic Ocean and spread to the Southern Hemisphere in the Oligocene. The spread (or migration) of Goniothecium species from North to South and vice versa might have been influenced by changes in the thermohaline circulation and ocean current structure across the Eocene/Oligocene boundary. Since diatoms live in the euphotic zone, transportation of living cells over long distances most likely occurs by surface (or intermediate) water currents, however, more resistant resting spores may be laterally advected by bottom water currents.