Sphaeropylolena laxa, 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 : 39-40

Sphaeropylolena laxa n. sp.

Figure 22

zoobank.org/ 4901699A-6BE3-4465-8AA3-1796B6E8EBE7

1982 Larcoids gen. et sp. indet. Nakaseko and Nishimura, pl. 27, fig. 5.

1995 Phorticium circumtextum (JØrgensen); van de Paverd, p. 198, pl. 59, fig. 2.

Etymology. The Latin adjective “laxus” (-a, -um),

meaning loose.

Holotype. Specimen in Figure 22.3-4 from the sample YDY05-01.

Paratype. Specimen in Figure 22.1-2 from the sample YDY05-01.

Description. The aperture of the 1st pseudo-concentric shell is closed or resembles a normal latticed pore frame. More than eight (likely 12) radial spines extend from both sides of the central combination, and extend from the boundaries between the three girdles with visible longitudinal sides on the Sg-view, as well as from the remaining three girdles. These radial spines are twice as long as the width of the 1st pseudo-concentric shell. The 2nd pseudo-concentric shell is composed of several girdles (the exact number of girdles is unknown). Two sets of girdles develop from both lateral sides of the 1st pseudo-concentric shell. These girdles attach to larger girdles. The 2nd pseudo-concentric shell is twice to three times larger than the 1st pseudo-concentric shell and has various shapes, such as a rounded triangle, pentagon, or a hexagonal sphere, when viewed from different orientations. Pores in the 2nd pseudo-concentric shell are polygonal to quadrangular in shape. Pores of the central combination are 5–10

ZHANG & SUZUKI: TAXONOMY OF HOLOCENE PYLONIOID

μm in diameter, those of the 1st pseudo-concentric shell are 8–15 μm, and those of the 2nd pseudo-concentric shell are 25–50 μm. The larger pores of the 2nd pseudo-concentric shell are partially derived from apertures and tunnels of gates.

Remarks. Sphaeropylolena laxa n. sp. is easily distinguished from Sphaeropylolena circumtexta ( JØrgensen, 1899) and Sphaeropylolena tenellispinosa n. sp. based on its loosely spiraled girdles and the larger pores of the 2nd pseudo-concentric shell, as well as its long, robust radial spines.

Dimensions. Based on the holotype specimen. The width of the 1st pseudo-concentric shell: 55.8 μm; The width of the 2nd pseudo-concentric shell: 142.1 μm. The width ratio of the the 2nd pseudo-concentric shell to the 1st pseudo-concentric shell: ca. 2.5. Diameter of pores: 5–10μm (the central combination), 8–15 μm (1st pseudo-concentric shell), and 25–50 μm (2nd pseudo-concentric shell).

Figures

FIGURE 22. Photographs of the encountered morphotypes of Sphaeropylolena laxa n. sp. All are Fr-view at Type 2. Scale bar equals 0.1 mm. All specimens are from YDY05-01.