Larcospira tetragonicentrum, Zhang & Suzuki, 2017

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 : 25

Larcospira tetragonicentrum n. sp.

Figure 14

zoobank.org/ B201D0B4-5D56-42DA-8758-7A439673EE2E

1995 Phorticium ? sp. van de Paverd, pl. 57, fig. 5. 1994 Larcospira quadrangula Haeckel ; Kim, Park, and Park, pl. 2, fig. 11.

1994 Larcospira quadrangula Haeckel ; Hatakeda and BjØrklund, pl. 3, fig. 4.

Etymology. The Latin adjective “tetragonus” (-a, - um) and neutral noun “centrum”, meaning quadrangular center.

Holotype. Specimen in Figure 14.3-4 from the sample YDY05-01.

Paratype. Specimen in Figure 14.1-2 from the sample YDY05-01.

Description. Test is oblong in shape and consists of a square central part and lobate latticed girdles (1st pseudo-concentric shell). The length ratio of the axis to the coiling axis (the Lt-axis) is 0.8. The 1st pseudo-concentric shell has twin outermost girdles connected with the opposite ends of the central part along the Lt-axis. The width ratio of the 1st pseudo-concentric shell to the central part is 3.2. Several pillar beams are directly connected to the 1st pseudo-concentric shell. These beams form convex depressions on the 1st pseudo-concentric shell that give the shell a lobate appearance. These pillar beams may or may not penetrate. Secondary spines develop somewhat on the surface of the 1st pseudo-concentric shell. Pores are small on the central part and are large on the 1st pseudo-concentric shell. Pores on the 1st pseudo-concentric shell are polygonal in shape with fine pore frames.

Remarks. Larcospira tetragonicentrum n. sp. is similar to Larcospira quadrangula except that the former has only a single pseudo-concentric shell and a quadrangular central part. No other Larcospira species have a square central part; consequently, we concluded that this morphotype belongs to a new species.

Dimensions. Based on the holotype specimen. The length and width of pseudo-concentric shell: 9.5 μm and 9.1 μm (microsphere), 31.1 μm and 26.9 μm (central part), and 106.5 μm and 84.8 μm (1st pseudo-concentric shell). The ratio of the length to the width: 1.0 (microsphere), 1.2 (central part), and 1.3 (1st pseudo-concentric shell). The width ratio of the 1st pseudo-concentric shell to the central part is ca. 3.2. The width ratio of the central part to the microsphere is ca. 3.0.

Figures

FIGURE 14. Photographs of the encountered morphotypes of Larcospira tetragonicentrum n. sp. All are Pl-view at Type 1. Scale bar equals 0.1 mm. All specimens are from YDY05-01.