Phorticium scitulum, 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 : 45-47

Phorticium scitulum n. sp.

Figure 26

zoobank.org/ 0B55A012-2DB2-4635-9BAB-485D695A4F12

Etymology. The Latin adjective “scitulus” (-a, -um), meaning good looking.

Holotype. Specimen in Figure 26.6-7 from the sample YDY05-01.

Paratype. Specimen in Figure 26.16-17 from the sample YDY05-01.

ZHANG & SUZUKI: TAXONOMY OF HOLOCENE PYLONIOID

Description. The test is circular to sub-circular in shape (the length ratio of the longest axis to the middle axis: ca. 1.0–1.2) from the Sg-view, and it consists of an oblong central combination, an elliptical 1st pseudo-concentric shell, a circular to subcircular 2nd pseudo-concentric shell with a large aperture on both sides of the test in Sg-view, numerous pillar beams between the central combination and 1st pseudo-concentric shell and between the 1st and 2nd pseudo-concentric shells, and numerous short radial spines. The 1st and 2nd pseudo-concentric shells are arranged in the same orientation. The 1st pseudo-concentric shell has two gates in its juvenile form without the 2nd pseudo-concentric shell, and is completely latticed in its grown form with a partial 2nd pseudo-concentric shell. The ratio of the width of the 2nd pseudo-concentric shell along the Lt-axis to that along its Pl-axis is smaller than this ratio for the 1st pseudo-concentric shell. Many pillar beams are present between the 1st and 2nd pseudo-concentric shells. Some pillar beams from the 1st pseudo-concentric shell pierce through the 2nd to form short, cylindrical radial spines. Pores are subcircular and small (5–8 μm in diameter) on the 1st pseudo-concentric shell, and subcircular to polygonal in shape and moderate in size (8–13 μm in diameter) on the 2nd pseudo-concentric shell. Six or eight pores are aligned along the Lt-axis on the joint part between the 1st and 2nd pseudo-concentric shells, and 10 to 12 pores are aligned along the Pl-axis on the 2nd pseudo-concentric shell. Pore frames of the 1st and 2nd pseudo-concentric shells are very thin. The size ratio of the 2nd to the 1st pseudo-concentric shell is 1.9–2.6 along the Lt-axis and 1.9–2.5 along the Pl-axis.

Remarks. Phorticium scitulum n. sp. differs from Phorticium polycladum Tan and Tchang, 1976 in that the latter has a larger and more elongate test, a larger size ratio between the 2nd pseudo-concentric shell and the 1st pseudo-concentric shell, a lower number of pillar beams between the 1st and 2nd pseudo-concentric shells, larger pores on the 2nd pseudo-concentric shell, and more developed radial spines. Phorticium scitulum n. sp. is distinguishable from Phorticium multispinum Popofsky, 1912 , based on its four major radial spines that arise from the apical, basal and both lateral sides of the central combination.

Dimensions. Based on the holotype specimen. The length along the Lt-axis: 95.0 μm (2nd pseudo-concentric shell), 42.9 μm (1st pseudo-concentric shell); The length along the Pl-axis: 89.1 μm (2nd pseudo-concentric shell), 36.9 μm (1st pseudo-concentric shell); The size ratio of the 2nd pseudo-concentric shell to the 1st pseudo-concentric shell: ca. 2.2 along the Lt-axis and ca. 2.4 along the Pl-axis. Diameter of pores on the 1st pseudo-concentric shell: ca. 5–8 μm; Diamter of pores on the 2nd pseudo-concentric shell: ca. 8–13 μm.

Figures

FIGURE 26. Photographs of the encountered morphotypes of Phorticium scitulum n. sp. 1-23, Sg-view at Type 1. Scale bar equals 0.1 mm. All specimens are from YDY05-01.