Syracosphaera periperforata var. tridentata Archontikis, Young, Cros, 2020

Archontikis, Odysseas A., Young, Jeremy R. & Cros, Lluïsa, 2020, Taxonomic Revision and Classification of Extant Holococcolithophores Previously Placed in the Genus Anthosphaera Kamptner emend. Kleijne 1991, Acta Protozoologica 59, pp. 121-139 : 134

Syracosphaera periperforata var. tridentata Archontikis, Young, Cros var. nov. HOL

Derivatio nominis: From Latin tridentatus –a –um (adjective), from trident, the three-prong weapon; refer- ring to the three-pointed upper structure of CFCs.

Description: Coccosphere, spherical but usually seen collapsed, composed of c. 50–85 BCs and c. 6–10 CFCs. BCs broadly elliptical with a rim of one to two microcrystals wide. Perforate cycle irregular with c. 8 large perforations, separated by narrow struts, which usually do not show obvious obliquity. The central structure dome-shaped with a low apical boss. CFCs subcircular to circular in outline. A single-layered distal process, whose opening in the arch is placed low, bears an upper margin structure with three pointy edges; the rim shows one to two rings of crystallites.

Remarks: The central structure of the BCs is similar to that of S. periperforata var. periperforata with a conical shape and an apical boss. However, the perforate cycle is less regular and bears less struts. The CFCs are also different, showing a characteristic upper margin structure with three pointy edges and a low arch.

Dimensions: Coccosphere diameter c. 7.5 μm. BCs c. 0.9–1.1 μm long x c. 0.8–1.0 μm wide. CFCs c. 1.0– 1.2 μm long and wide; distal process maximum 1.0 μm high and wide.

Holotype: Specimen illustrated in JRYSEM-303-76 ( Plate 4 , Fig. 5), stub TS 17-8-09, curated at the NHM, London, UK.

Paratype: Specimen illustrated at Plate 4 , Fig. 6.

Type locality: Station RV 001, 10m water depth, col- lected off Rovinj , northeastern Adriatic Sea (45°04N, 13°63E) on 17 August 2009 .

Number of specimens studied: 7

Distribution: Sub-tropical waters

Figures

Plate 4. Syracosphaera periperforata (Kleijne) Archontikis, Young, Cros comb. nov. HOL Scale bars = 1μm