Achnanthidium craterianum MOTS CLES Marquardt & C. E. Wetzel 2023, sp. nov.
Creators: name: Marquardt, Gisele C.
name: Bicudo, Denise C.
name: de M. Bicudo, Carlos E.
name: Ledru, Marie-Pierre
name: Wetzel, Carlos E.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Chromista
Bacillariophyta
Bacillariophyceae
Achnanthales
Achnanthidiaceae
Achnanthidium
Achnanthidium craterianum

description: Achnanthidium craterianum Marquardt & C.E.Wetzel, sp. nov.
(Figs 5-8)
HOLOTYPE. — Brazil. São Paulo, SP, Parelheiros District, Colônia crater, 23°52’S, 46°42’20”W, 900 m a.s.l., from sample 4268- 69 cm liner depth (c. 1.37 Ma; 4311 composite depth) of the COL17-3 sediment core, VIII.2017, M.-P. Ledru & A.O. Sawakuchi (SP[SP514.067]!).
ISOTYPE. — Same data as holotype (BR [BR4737]!).
TYPE LOCALITY. — Brazil. São Paulo, SP, Parelheiros District, Colônia crater, 23°52’S, 46°42’20”W, 900 m a.s.l.
ETYMOLOGY. — The Latin name craterianum refers to the Colônia Basin geomorphological structure where the sample was collected.
ECOLOGY AND DISTRIBUTION. — Achnanthidium craterianum Marquardt & C.E.Wetzel, sp. nov. was abundant in the core (60% relative abundance). Accompanying taxa included mainly Aulacoseira ambigua (28%) and Staurosira sp. 1 (5%) as dominant species.
DESCRIPTION
LM observations (Fig. 5)
Frustule girdle in view is rectangularly arched,with pointed apices slightly curved (Fig. 5 AI, AJ). Valves linear to linear-lanceolate, with margins almost parallel to only slightly widening toward the central area. Sub-capitate to capitate apices, protracted (Fig. 5 A-AH), facing opposite directions (Fig. 5 B-O, R-AH); 8.5-19.0 µm long, 2.0-2.5 µm wide. Raphe valve: narrow to faintly lanceolate axial area toward the central area; rounded central area, with 2-4 shortened striae on both sides of the valve (Fig. 5 A-U). Straight raphe filiform. Transapical striae slightly radiating throughout the entire valve, more spaced in the central area, becoming denser and more strongly radiating toward the apices (Fig. 5 A-U); 32-33 in 10 µm. Rapheless valve: narrow, linear axial area, sometimes faintly lanceolate toward the central area; absent central area or narrow lanceolate (Fig. 5 V-AH). Transapical striae slightly radiate throughout the entire valve, more spaced in the central area, becoming denser towards the apices; 40-42 in 10 µm. Rectangular arcuate girdle view, with pointed apices slightly recurved to the rapheless valve(Fig.5 AI-AJ).
SEM observations (Figs 6-8)
Raphe valve: raphe prolonged after the striae, terminating on the border between the valve face and mantle (Fig. 6 A-C). Central and terminal raphe fissures are straight and slightly expanded at the endings (Fig. 6 A-D). Striae composed of 2-3 rounded areolae, becoming denser toward the apices (Fig. 6 A-C). Internally, proximal raphe endings slightly deflected in opposite directions, distal endings terminating in small helictoglossae (Fig. 6 A-C). Rapheless valve: very narrow axial area, lanceolate towards the central area (Figs 6E, F; 7D). Striae composed of 2-3 rounded to slit-like areolae (Fig. 6E, F). Mantle with one row of slit-like transapically orientated areolae (Figs 6F; 8 A-C).
description: Published as part of Marquardt, Gisele C., Bicudo, Denise C., de M. Bicudo, Carlos E., Ledru, Marie-Pierre & Wetzel, Carlos E., 2023, Two new species of Achnanthidium Kützing (Achnanthidiaceae) from the Quaternary sediments of the Colônia basin, Southeast Brazil, pp. 111-126 in Cryptogamie, Algologie 20 (6) on pages 116-118, DOI: 10.5252/cryptogamie-algologie2023v44a6, http://zenodo.org/record/8399144