Larcospira, Haeckel, 1887

Zhang, Lanlan & Suzuki, Noritoshi, 2017, Taxonomy and species diversity of Holocene pylonioid radiolarians from surface sediments of the northeastern Indian Ocean, Palaeontologia Electronica (Cambridge, England: 2003) 7 (8), pp. 1-68 : 21

Genus LARCOSPIRA Haeckel, 1887

* 1887 Larcospira Haeckel , p. 695-696.

2001 Larcospira Haeckel ; De Wever, Dumitrica, Caulet, Nigrini, and Caridroit, fig. 88.5, 88.6. Type species. Larcospira (Larcospirema) quadrangular Haeckel (SD by Campbell, 1954).

Description. Test is flat and either spindle-shaped or rounded quadrangular in shape, and has spiral spindle-shaped girdles along a single long axis. This axis is equivalent to the Lt-axis under Type 1 coordinates. The central part consists of a pyloniid central combination and G1 girdle, which form the first pseudo-concentric shell. The Lt-axis of the central combination is equivalent to the revolving axis of the test and parallel to the longest axis of the test. Because there are no twin gates, the Fr-view cannot be separated from the Pr-view. The S1a-girdle encircles the central combination along the Lt-axis ( Fig. 11.6 , 7 ). The S1a-girdle are ellipsoid in shape, and the Ug-axis under Type 2 coordinates is parallel to the long axis of the test (see Sugiyama et al., 1992, plate 9, figures 2b and 4c; De Wever et al., 2001, figure 88.5). The girdles coil to form the 2nd and 3rd pseudo-concentric shells. The previous girdles are attached at both ends of the Lt-axis with the successive girdles. Several pillar beams emerge vertically from the 1st pseudo-concentric shell, extending to but not penetrating the 3rd one.

Remarks. Despite detailed examination of the internal structure of the genus Larcospira (e.g., Sugiyama et al., 1992), formally updating its description has been suspended. It may be essential to examine the internal structure to determine whether a species belongs to the genus Larcospira , but Larcospira species can be determined without examining the internal structure. Larcospira is easily distinguished from Tetrapyle based on its coiled girdles without gates. The known ancestor species of Larcospira , Larcospira moschkovskii Kruglikova, 1978 , is characterized by very tight coils, the same numbers of pseudo-concentric shells and a lack of radial spines, which suggests that Larcospira specimens may be distinguished from each other at the species level based on the shapes of their central parts, the numbers of revolving spiral girdles, the tightness of revolution, and the roughness of the outermost girdles in relation to pillar beams.

Figures

FIGURE 7. The typical Tetrapyle octacantha specimens from the surface water from the southern Villefranche-sur- Mer. 1 and 6, Ug-view at Type 2; 2-3 and 8, Pr-view at Type 2; 4-7, Fr-view at Type 2. Scale bar equals 0.1 mm. The arrow marks indicate the major portal-spines.

FIGURE 11. Photographs of the encountered morphotypes of Tetrapyle spp. (juvenile form). 1-2 and 9, Lt-view at Type 1, Fr-view at Type 2; 3-5, 7-8, 11-12, Sg-view at Type 1, Fr-view at Type 2; 6 and 10, Pl-view at Type 1, Fr-view at Type 2; 13-14, Pl-view at Type 1, Ug-view at Type 2; 15-16, Sg-view at Type 1, Fr-view at Type 2; 17-18, Sg-view at Type 1, Ug-view at Type 2. Scale bar equals 0.1 mm. All specimens are from YDY05-01.