Tholomura pilula, 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 : 59

Tholomura pilula n. sp.

Figure 32.12-23

zoobank.org/ C9B27FD8-534C-4B0F-AC43-920FF7E69BB0

Etymology. The Latin feminine noun “pilula ” (-ae), meaning a small sphere.

Holotype. Specimen in Figure 32.22-23 from the sample YDY05-01.

Description. Test is spherical in shape with an S1a (microsphere), an ellipsoid 1st pseudo-concentric shell, and a spherical 2nd pseudo-concentric shell. No gates are present. The S1a appears elliptical from the Lt-view and circular from the Pl-view. The 1st pseudo-concentric shell comprises two 1st girdle-like cupolas that develop along the Lt-axis and two 2nd girdle-like cupolas that develop along the Sg-axis; these four girdle-like cupolas are completely connected to each other to form a closed, latticed pseudo-concentric shell. The 1st pseudo-concentric shell looks elliptical from the Pl- and Ltviews, and rounded quadrangular from the Sg-view. Pores of the 1st pseudo-concentric shell are circular to sub-circular in shape with relatively fine pore frames. Polar beams, an apical rod and a basal rod emerge from the S1a to pierce through the 1st pseudo-concentric shell. The 2nd pseudo-concentric shell comprises six cupolas to form a completely closed, latticed sphere. The 2nd pseudo-concentric shell is sub-spherical in shape. Six main cylindrical spines and eight polar spines extend linearly. The suture of the 2nd pseudo-concentric shell is visible under transmitted light microscopy but does not form depressions. Pores of the 2nd pseudo-concentric shell are polygonal in shape with fine pore frames.

Remarks. Tholomura pilula n. sp. is easily distinguished from all other species of Tholomura because it has a nearly complete spherical pseudo-concentric shell without fine coverage. Tholomura pilula n. sp. differs from Tholomura hexonia ( Haeckel, 1887) in that it has finer pores and apparent sutures between its cupolas. Tholomura pilula n. sp. appears to have three pseudo-concentric shells without clearly main or polar spines. These morphological characteristics may lead us to mistake specimens of this taxon as a member of Thecosphaera ; however, T. pilua n. sp. is different from Thecosphaera in its pyloniid internal structure. Dimensions. Based on the holotype specimen. The length and width of the 1st pseudo-concentric shell: 38.8 μm and 26.6 μm; The length and width of the 2nd pseudo-concentric shell: 68.8 μm and 67.7 μm. The ratio of length to width: ca. 1.5 (1st pseudo-concentric shell) and ca. 1.0 (2nd pseudo-concentric shell).

Figures

FIGURE 32. Photographs of the encountered morphotypes of Tholomura. 1-11, Tholomura hexonia (Haeckel, 1887); 12-23, Tholomura pilula n. sp.; 24-32, Tholomura polystyla (Chen, 1987). 1-16, 19-23, 26-32, Pl-view at Type 1; 17- 18, 24-25, Lt-view at Type 1. Scale bar equals 0.1 mm. All specimens are from YDY05-01.