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Authority

Castrac. (Castracane, 1886: 71, pl. 74, fig. 2)

Class

Diatomophyceae

Order

Centrales

Family

Rhizosoleniaceae

Synonyms

Rhizosolenia styliformis var. oceanica Wimpenny (1946: 279, text fig. 1d, e)
Rhizosolenia styliformis auct. non Brightwell (1858), sensu Hendey (1937: pl. 11, figs 15–17)
Rhizosolenia styliformis var. longispina auct. non Hustedt (1934), sensu Okuno (1952, pl. 2, fig. 1)

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Basionym

N/A

Additional References

Sundström (1986: 24, figs 7, 70–72, 74, 76, 77, 79), Priddle et al. (1990: 118, pl. 15.2, figs 4, 5), Hasle & Syvertsen (1997: 150, pl. 27, tab. 33), Armand & Zielinski (2001: pl. 3A, figs 6–9, as f. polydactyla; pl. 3B, figs 2, 3, as f. squamosa)

Description

Cells usually solitary, long, cylindrical. Valves conical, bilaterally symmetrical; apical axis 15–105 µm (56–105 µm in f. squamosa); areolae 26–28 in 10 µm. Process 18–34 µm long, tapering distally from c. midway along its length. Otaria large, rounded, ending clearly above the base of the process and at right-angles. Contiguous area and claspers conspicuous. Girdle bands forming 2 dorsiventral columns of segments, areolate; areolae 20–23 in 10 µm.

Distribution

Southern cold-water regions (Hasle & Syvertsen, 1997); Marguerite Bay, Bellingshausen Sea and Amundsen Sea (Mangin, 1915); Bellingshausen Sea, South Georgia, Drake Passage (Hendey, 1937).

Comments

Rhizosolenia polydactyla f. squamosa Sundström is generally regarded as the otaria-lacking resting spore of R. polydactyla f. polydactyla. However, the girdle bands of f. squamosa form several pairs of segment columns, and the valves are of a coarser structure than in f. polydactyla. While the former lacks otaria, the rimportula is heavily silicified. An intermediate form was illustrated by Priddle et al. (1990: pl. 15.2, fig. 6). Sundström (1986) listed R. styliformis var. latissima Brightw. ex Freng. & Orlando (Frenguelli & Orlando, 1958: 17, fig. 6) as a synonym of R. polydactyla f. squamosa.

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