Palusphaera crosiae Archontikis & Jer.R. Young, 2021

Archontikis, Odysseas A. & Young, Jeremy R., 2021, A reappraisal of the taxonomy and biodiversity of the extant coccolithophore genus Palusphaera (Rhabdosphaeraceae, Prymnesiophyceae), Phycologia 60 (6), pp. 589-602 : 596-597

Palusphaera crosiae Archontikis & Jer.R. Young sp. nov.

Figs 17–21

PREVIOUS RECORDS UNDER MISAPPLIED NAMES: sp. aff. Palusphaera sensu Kleijne (1992, p. 38, described under remarks on Palusphaera but not illustrated). Palusphaera sp. 1 (type robusta) sensu Cros (2002, p. 36, pl. 9, figs 4, 6); Cros & Fortuño (2002, p. 84, figs 22C, 22D); Young et al. (2003, pp 56–57, pl. 25, figs 10, 11); Malinverno et al. (2008, p. 66, fig. 37). Palusphaera vandelii var. crassa sensu Dimiza (2006 , pp 61–62, pl. X, figs 5–6 and pl. XI, figs 1–6, unpublished PhD thesis, invalid).

DESCRIPTION: Coccosphere, monomorphic and generally seen collapsed but probably spherical in shape, with c. 45–60 BCs. BC bases broadly elliptical in outline and slightly concavo-convex. Rim shows typical Rhabdosphaeraceae rim structure. Central area filled by the lamellar cycle; no radial cycle is present. Central process is a long, tapering spindleshaped spine. Maximum thickness is at one-third to one-quarter of the height and it tapers to a fine point. The spine is formed from robust laths, c. 1.0 μm × 0.15 μm at the base, becoming smaller towards the tip; they abutt neatly to form a 6- to 8-μm sided smooth hollow structure. Adjacent laths are offset by about one-third of their length. BC proximal side with a central pore surrounded by a few angular nodes.

DIMENSIONS: Coccosphere diameter c. 5–9 μm without processes and c. 15–25 μm including processes. BCs c. 1.2–2.0 μm × c. 1.0 μm; rim is c. 0.2 μm. Spine c. 6 μm long.

HOLOTYPE: 200-07 (specimen illustrated in Figs 17–18 ), stub no. 470/3, deposited at the collections of the Natural History Museum, London under the designation PM NF 4917 200-07 .

PARATYPES: 211-21 (stub no. 487/0, designation PM NF 4855 211-21 ); 211-22 (stub no. 487/0, designation PM NF 4855 211-22 ); 177-56 (stub no. 302/2, designation PM NF 4663 177-56 ). Specimens of these stubs are illustrated by Figs 19–21 .

TYPE LOCALITY: North-western Mediterranean and Alboran Seas (37° 25.98'N, 0°25.3'W, depth 70 m, October 1999, MATER II Expedition, Station 69-08).

DISTRIBUTION: Subtropical waters.

NUMBER OF SPECIMENS STUDIED: Nine, plus two published in Cros & Fortuño (2002).

ETYMOLOGY: After Dr. Lluïsa Cros (Institut de Ciències del Mar, CSIC), who first illustrated the taxon, and in recognition of her many contributions to extant coccolithophore taxonomy.

REMARKS: The species differs from the other taxa in possessing a styliform spine with robust and thick lath-like crystal segments, markedly thicker at the one-third to one-quarter height from the base of the central area. The distal side outer rim cycle is distinctly narrower compared to that of P. vandelii .

Figures

Figs 17–21. SEM micrographs of Palusphaera crosiae sp. nov. Scale bar = 5 μm for Figs 17, 18, 19. Fig. 17. Holotype and complete coccosphere. Fig. 18. Detailed view of Fig. 17; arrow indicates the part of the spine being markedly thicker at the one-third to one-quarter height from the base. Fig. 19. Complete coccosphere with subcircular planoliths. Fig. 20. Detailed view of Fig. 19; planoliths with (a) a relatively wide outer rim cycle, (b) a styliform spine formed at the centre of the lamellar cycle in distal side, and (c) three robust angular nodes surrounding the central pore in proximal side. Scale bar = 2 μm. Fig. 21. Side view of styliform processes of disarticulated spine-bearing planoliths. Scale bar = 1 μm.