Two new species of Staurosira and Pseudostaurosira (Bacillariophyta) from the highlands of Argentina (south-central Andes) and two new nomenclatural combinations

Abstract

Two new araphid diatom (Bacillariophyta) species, Pseudostaurosira oliveraiana sp. nov. and Staurosira catamarcensis sp. nov. are described from fossil material taken from the saline Laguna Colorada (Argentinian Altiplano). The morphology of the new species is studied using both light (LM) and scanning electron microscopy (SEM) and is compared to that of similar taxa. Pseudostaurosira oliveraiana sp. nov. is different from other species of Pseudostaurosira by its linear to lanceolate valve outline, with apices usually subcapitate and cuneate. Staurosira catamarcensis sp. nov. is unique because it has short striae that are restricted to the valve margins, delimiting a wide and lanceolate sternum, which resembles some species of Pseudostaurosira. Also, it is the first species described in Staurosira lacking apical pore fields, expanding the high morphological variation that already exists within this genus. Additionally, two new combinations are proposed: Pseudostaurosira santaremensis comb. nov. and Staurosirella canariensis comb. nov. based on information at the SEM and LM level presented in the literature.