Tholomura polystyla ( Chen, 1987 )

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 : 60

Tholomura polystyla ( Chen, 1987)

Figure 32.24-32

1973 Tholoniidae sp. BjØrklund, pl. 1, fig. R.

1974 Cubotholus sp. Ieda, pl. 3, fig. 5a-b.

1977 Cubotholus cf. rhombicus Haeckel ; Casey and McMillen, pl. 1, fig. 14.

1978 Cubotholus rhombicus Haeckel ; McMillen and Casey, pl. 3, fig. 19 (the same specimen with Casey and McMillen, 1977, pl. 1, fig. 14).

*1987 Cubotholonium polysytulum Chen , p. 225- 226, pl. 2, figs. 8-9.

1987 Amphitholonium transversarum Chen , p. 225, pl. 2, figs. 10-11.

1988 Amphitholonium transversarum Chen ; Tan, p. 272-273, text-fig. 260.

1999 Amphitholonium transversarum Chen ; Tan and Chen, p. 259, text-fig. 5.172.

1991 Tholomura metallasson Haeckel ; Takahashi, p. 89, pl. 11, figs. 12-13.

1992 Larnacillidae ? gen. et sp. sp. indet. A. Sugiyama, Nobuhara, and Inoue, pl. 11, figs. 5, 7-8.

1995 Amphitholus metallasson (Haeckel) ; van de Paverd, pl. 53, figs. 9-10, 12?

1998 Amphitholus metallasson (Haeckel) ; Danelian and Frydas, pl. 3, fig. 15.

2014d Tholomura polystyla (Cheng) (misspelling to the author’s name); Matsuzaki, Nishi, Suzuki, Takashima, Kawate, and Sakai, pl. 2, fig. 9.

2015a Tholomura polystyla (Chen) ; Matsuzaki, Suzuki, and Nishi, p. 36-37, fig. 6.18 (Refer to Matsuzaki, Suzuki, and Nishi [2015a] for other synonym lists).

Description. Test consists of a spherical S1a

(microsphere), an ellipsoid 1st pseudo-concentric shell, and two levels of three sets of twin, relatively tall, dome-shaped cupolas. No gates are present.

The sutures between cupolas are very deep.

Transverse sections of the cupolas along a given plane show at least two large, subcircular outlines of cupolas. Pores of cupolas are polygonal to rounded polygonal with relatively fine pore frames. Polar beams extend along both sides of the Lt-axis from the S1a, but they do not pierce through the outermost cupolas. Fourteen straight, cylindrical main spines arise from the joint zones of the cupolas, but these main spines develop only in the latest stage of ontogenetic growth after the full development of two levels of three sets of twin dome-shaped cupolas.

Remarks. “ Amphitholonium transversarum Chen, 1987 ” is a Pl-view of Tholomura polystyla ( Chen, 1987) , whereas “ Cubotholonium polystylum Chen, 1987 ” is a Lt-view of the same. The radial spines develop after the development of the 2nd pseudo-concentric shell, and consequently, it is unlikely that the presence/absence of radial spines could be effectively applied in as a taxonomic criterion. Tholomura polystyla differs from Tholomura hexonia in having the very deep sutures between the cupolas, the more spherical dome-shaped cupolas (the length ratio of cupola width to height = 1.7–3.3 for T. hexonia and 1.2–1.9 for T. polystyla ).

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.