THE FOSSIL DIATOM GENUS TRUANIA PANTOCSEK AND ITS RELATIONSHIP WITH ELLERBECKIA CRAWFORD

Abstract

The rare taxon, Truania archangelskiana Pantocsek has been examined from slides and material in the Natural History Museum, London, and from slides in the Hustedt Collection, Bremerhaven, all of it Russian. This marine fossil from the Late Cretaceous and Palaeocene shows strong similarities with species of Ellerbeckia Crawford with which it shares the characteristic mantle edge, valvocopula and mantle structure but differs in not having the linking valve/separation valve heterovalvy. It probably existed as single cells because cameo and intaglio features occur on both sibling valves. The tube processes are enigmatic and may indicate a stage of evolution before the porelliportula characteristic of Ellerbeckia. Preliminary remarks regarding family relationships are made.