Cyclocostis Paillès, 2020

Paillès, Christine, Sylvestre, Florence, Tonetto, Alain, Mazur, Jean-Charles & Conrod, Sandrine, 2020, New fossil genus and new extant species of diatoms (Stephanodiscaceae, Bacillariophyceae) from Pleistocene sediments in the Neotropics (Guatemala, Central America): adaptation to a changing environment?, European Journal of Taxonomy 726, pp. 1-23 : 4

Genus Cyclocostis Paillès gen. nov.

Type species

Cyclocostis rolfii Paillès gen et sp. nov. (see below).

Diagnosis

A new morphotypic genus of Stephanodiscaceae . Cells solitary, circular in valve view. Marginal and central areas coarsely striated with branching striae merging in the middle of the valve into a central punctum. Central area strongly tangentially undulated, focus clear only on half the central area. Submarginal alveoli finely punctuated, transforming into radiating rows of large irregular areolae in the central area. Internally, alveoli delineated by thick elevated costae reaching the valve center to form a subcircular silica ring. Alveoli widely open with a median recessed costa bearing marginal fultoportulae. Central lamina absent. Single rimoportula within a ring of marginal fultoportulae reduced to a rounded tube tangentially orientated and born on a recessed costa. On the mantle, outer expressions of marginal fultoportulae and rimoportula consisting of simple rounded openings without projections. One single valve face fultoportula consisting of a central tube surrounded by three satellite pores that opens externally into a round opening on the raised part. Cingulum present consisting of an open valvocopula and several copulae.

Etymology

The genus name refers to the circular morphology of the valve and marked radiating costae.