Syracosphaera rotaconica 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 : 134-137

Species Syracosphaera rotaconica Archontikis, Young, Cros sp. nov. HOL

Synonymy: Anthosphaera periperforata sp. type 3 Cros (2001), p. 81, Pl. 56, Figs. 5–6; Cros and For- tuño (2002), p. 60, Fig. 87D; Young et al. (2003), p. 90, Pl. 42, Figs. 7, 10.

Derivatio nominis: From Latin rota (noun), wheel, and conicus –a –um (adjective), conical; referring to the chiral-conical structure of the BCs.

Description: Coccosphere spherical shape, usually seen collapsed, composed of 30–80 nearly flat BCs and 5 – 10 CFCs. BCs’ elliptical rim formed of two rings of small crystallites and perforate cycle well-developed with c. 20 struts showing distinct anticlockwise obliquity. These form a simple cone with an apical boss on top of the distal cover. The struts are well-separated by prominent and large, nearly triangular perforations. CFCs consist of a similarly structured rim that bears a distal arched process with a low point via crystal struts. The central pointy edge is somewhat higher than the lateral ones.

Remarks: BCs’ central structure is conical in shape and similar to that of S. periperforata var. periperforata , but smaller. The perforate cycle is made by large struts of crystallites; BCs’ rim is of two crystallites wide as opposed to one of the S. periperforata var. periperforata rim width.

Dimensions: Coccosphere diameter c. 7.5 μm. BCs 1.0 μm long x 0.8 μm wide. CFCs c. 1.3 μm long x 0.8 μm wide; CFCs’ distal process c. 1.0 μm high.

Holotype: Negative nº 140419 ( Plate 5 , Fig. 1 ), cu- rated at the ICM (CSIC), Barcelona, Spain.

Paratype (s): Specimens illustrated at Plate 5 , Figs. 3–4 .

Type locality: Station Meso-96 E3/4, 40 m wa- ter depth, collected from the NW Mediterranean Sea (41º23.0N 3º10.2E), cruise Meso-96, 1 July 1996.

Number of specimens studied: 7

Distribution: Sub-tropical waters

Figures

Plate 3. Scale bars = 1μm 1–2. Syracosphaera lafourcadii (Lecal) Archontikis, Young, Cros comb. nov. HOL Complete coccospheres composed of CFCs that bear low distal processes (see arrows) and BCs with distal covers made of irregularly ar- ranged crystallites. 3–4. Syracosphaera origami (Cros and McGrane) Archontikis, Young, Cros comb. nov. HOL Coccospheres with highly ornamented CFCs showing triangle-shaped distal processes (fig. 3, arrow) and BCs with an organic base-plate in proximal view (fig. 4, arrow a) and a rim that supports delicate struts of crystallites holding the origami-like paper boat distal covers (fig. 4, arrow b) in distal view.

Plate 5. Syracosphaera rotaconica Archontikis, Young, Cros sp. nov. HOL Scale bars = 1μm 1. Holotype; flattened coccosphere with chiral-conical BCs that usually show a small apical boss on top of the central distal cover. BCs’ central structure is made of numerous crystal struts, progressively meeting and forming the distal cover. 2. Detail of figure 1 showing the ultrastructure of BCs. 3. Paratype; coccosphere showing the delicate structure of CFCs (see arrow). 4. Paratype.

Fig. 1. Map of the sampling locations, where Anthosphaera was observed.