New Aulacoseira species (Bacillariophyta) from the Argentinean Patagonia and reexamination of type material of Melosira perpusilla Frenguelli

Abstract

We present a detailed morphological analysis with light and scanning electron microscopy of two new small Aulacoseiraspecies occurring in lacustrine sediments from small lakes in the provinces of Santa Cruz and Neuquén (Patagonia, Argentina).These species differ from similar taxa by unique combinations of characters. Aulacoseira lauquenensis sp. nov. can bedifferentiated by its broad collum, deep and solid ringleist and presence of short, spatulate and forked-tip spines. Aulacoseiraliucoensis sp. nov. is distinguished by the presence of a marginal row of valve face areolae, straight mantle rows of coarseareolae, developed collum, protruding ringleist and conical, anchor-tip spines. Additionally, we re-examine the type materialof Melosira perpusilla Frenguelli and present an analysis of its identity.