Two new species of Pseudostaurosiropsis (Bacillariophyta, Fragilariophyceae) from the United States of America, with taxonomic comments on the genus

Abstract

Two new species of Pseudostaurosiropsis are described based on material collected from rivers in southern UnitedStates of America, P. californicus sp. nov. and P. elaboratus sp. nov. Both species have specific characters that set themapart from taxa currently ascribed to the genus. Pseudostaurosiropsis californicus sp. nov. has lanceolate valves with subrostrate, broadlyrounded apices, an axial area at the same level as the virgae in internal and external views and both are at the same levelas striae in external view, the spine tips are dentate and their growth is produced by filamentous extensions, and it hasequal-sized apical pore fields on both valve extremes. On the other hand, P. elaboratus sp. nov. has heavily silicifiedvalves, the virgae are slender than the striae in outer view and wider in inner view, it only has a single, externally occludedapical pore field on one valve extreme, and the spines have a solid core. All species within Pseudostaurosiropsis are contrastedwith one another and unique features are described for each based on literature and newly collected image datafrom type material. The genus is reconsidered and two distinguishing features are recognized: rotae externally occludingthe areolae and areolae that are funnel-shaped. These features are contrasted with those in other genera and additionalpublished species that should be included in Pseudostaurosiropsis are discussed.