Nannotax3 - ntax_main - Syracosphaera winteri

Citation: Syracosphaera winteri Keuter et al. 2021

Basionym: Syracosphaera winteri Keuter et al. 2021

Synonyms:

Syracosphaera sp. A of Winter et al., 1979
Syracosphaera sp. on EMIDAS database (www.emidas.ethz.ch)

Taxonomic discussion: The exothecal coccoliths of this species are very distinctive. They were first observed by Winter et al. (1979) and have occasonally been observed since but entire coccospheres are rare so it was not formally described until 2021. The body coccoliths place it within the S. noroitica type.

Distinguishing features:
Parent taxon (noroitica type): BCs with proximal flange only, weakly developed inner wall. Coccospheres are highly varimorphic, the apical BCs have a robust central structure, this decreases toward the antapical area where there are BCs without a central structure. CFCs spine-bearing, with bifurcate tip. XCs muroliths.
This taxon: XCs - cup-shaped, lath cycle extended to form conical lower part of lith

Coccospheres - The observed coccospheres are all collapsed and probably in- complete (Fig. 1a–c). The scatters are ca. 20–30 μm across, and an intact coccosphere would probably be about 20 μm across and either equant or slightly elongated. The exothecal coccoliths form a complete cover and are arranged opening outwards; in this orientation their conical shape would al- low them to fit together neatly. The endotheca is formed of muroliths which vary in both size and spine development. A few large (ca. 3.5 μm) circum-flagellar coccoliths with long (3.5–4.5μm) spines appear to occur at the flagellar pole. They are surrounded by similar-sized body coccoliths with shorter spines, whilst smaller body coccoliths without spines occur towards the antapical pole of the cell. The variation in coccolith size and spine development in the body coccoliths is gradational. [Keuter et al. 2021]

Body Coccoliths - elliptical muroliths with proximal flange, flaring rim and smooth distal margin; they have a delicate grill of radial laths; central spine variably developed - absent on coccoliths a antapical end of coccosphere, higher toward apical pole up to 2 µm). Spines are formed of a bundle of 6 to 8 rod-like elements running the full length of the spine and giving it a star-shaped cross section. [Keuter et al. 2021]

Circum Flagellar Coccoliths - similar to BCs but have long (>3 µm) spines formed of numerous short elements. [Keuter et al. 2021]

Exothecal Coccoliths - basket-like in appearance; elliptical in plan view (3.5–5.5 μm long); cone-shaped in side view (3–4 μm high) with an open outer end and a flat truncated solid base. The rim of the coccolith is a rather robust structure (ca. 1 μm high × 0.2 μm wide). The lower part of the rim flares slightly, and the upper part tapers inward to form a lip around the top of the coccolith. In the flaring part of the rim the elements show anticlockwise imbrication; in the upper tapering part they show clockwise imbrication and strong dextral obliquity. A row of nodes occurs around the base of the rim. A slightly etched specimen (Fig. 2d) suggests that the rim is formed of two cycles of elements, but more observations are needed to determine the full structure.
The main part of the coccolith is formed of radial laths, which are elongate (up to 2 μm) but narrow (< 0.1 μm). There is one lath for each rim element and they meet the rim adja- cent to the nodes; on the inner surface they extend up the rim for 0.1–0.2 μm. At the rim the laths are well separated and a few of them run directly to the central plate. More commonly adjacent laths curve together to meet about half way down from the rim, then continue as composite structures formed of two to five laths. Toward the base of the coccolith the laths are deflected inward toward the central plate but still appear to consist of the same crystal units.
The central plate is typically a solid, flat, elliptical structure ca. 2 × 1.5 μm (Figs. 1d, 2b). It is formed of radiating elements without obvious chirality or imbrication, and each radiating element originates from a single element of the main lath cycle. In other specimens (Fig. 1d), the central plate is less complete and the continuity of the elements with the lath cycle is more obvious, which is similar to the structure of the central area in S. pulchra exothecal coccoliths (see Young et al., 2004). [Keuter et al. 2021]

Specimens observed come from the Red Sea, the Mediterranean, the North and South Atlantic Gulf of Mexico, and the Pacific and from 37°N (in the western Mediterranean) to 32°S (in the South Atlantic), suggesting that, despite its rarity, the species has a global distribution at subtropical and tropical latitudes. All specimens were collected from broadly oligotrophic sites with water depths varying from 12 to 170 m. Mostly the coccospheres were collected from the surface mixed layer, whilst isolated exothecal coccoliths were also observed from deeper water, and the coccosphere specimen of Winter et al. (1979) was collected from 150 m. Water temperatures for the samples varied between 17°C and 24.5°C. [Keuter et al 2021]

Geological Range:
Last occurrence (top): Extant. Data source: present in the plankton (Young et al. 2003)
First occurrence (base): within No known fossil record modern (0.00-0.00Ma, base in "Holocene" stage). Data source:

References:

Keuter, S., Young, J. R., Koplovitz, G., Zingone, A. & Frada, M. J. (2021). Novel heterococcolithophores, holococcolithophores and life cycle combinations from the families Syracosphaeraceae and Papposphaeraceae and the genus Florisphaera. Journal of Micropalaeontology. 40: 75-99. gs O

Winter, A., Reiss, Z. & Luz, B. (1979). Distribution of living coccolithophore assemblages in the Gulf of Elat ('Aqaba). Marine Micropaleontology. 4: 197-223. gs

Young, J. R., Geisen, M., Cros, L., Kleijne, A., Probert, I. & Ostergaard, J. B. (2003). A guide to extant coccolithophore taxonomy. Journal of Nannoplankton Research. S1: 1-132. gs

Syracosphaera winteri

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