Circodiscus amphitrites ( Ehrenberg, 1854b )

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 : 54

Circodiscus amphitrites ( Ehrenberg, 1854b)

Figure 31.1-2

nomen nudum

1854a Lithocyclia amphitrites . Ehrenberg, table.

*1854b Lithocyclia? amphitrites Ehrenberg , p. 244- 245.

1985 Lithocyclia? amphitrites Ehrenberg ; Boltovskoy and Jankilevich, pl. 2, fig. 18.

1987 Ommatodiscus murrayi Dreyer ; Dworetzky and Morley, pl. 2, fig. 6.

2009b Lithocyclia amphitrites Ehrenberg ; Suzuki, Ogane, Aita, Sakai, and Lazarus, pl. 33, figs. 1a-1e (type specimen in the Ehrenberg collection; lectotype herein).

Description. Test is a flat ellipsoid disk in shape (the length ratio of the Ug-axis to the Pr-axis = 1.2– 1.3) with a larnacillid central combination and 3–4 latticed wide rings. The exact direction of the central combination is unknown. Each ring from the Fr-view shows a smoothly curved outline. The wall of each ring is thick, and pore frames are robust with distinctive circular to subcircular pores. Pores are irregularly distributed throughout the test; two or three pores tend to be aligned with the width direction of a ring. The width of the rings increases in outward (10 μm in the 1st ring to 20 μm in the 3rd ring). Approximate 30 radial spines extend from the pillar beams on the Fr-plane.

Remarks. The type specimen of this species was illustrated in Suzuki et al. (2009b), and this specimen was designated herein as the lectotype. This lectotype was from surface sediment at a water depth of “10800’ fathoms” (ca. 19,751 m) in the Bay of Biscay, Atlantic Ocean (47°8 ʹN, 7°8 ʹW), presumed to be Holocene in age. Circodiscus amphitrites is easily distinguished from other Circodiscus species based on its longer elliptical outline, the gradually increasing width of the rings, and the thick wall of the test. The specific name “amphitrites ” is derived from the Greek god “amphitire” as a grammatically male noun.

Figures

FIGURE 31. Photographs of the encountered morphotypes of Circodiscus. 1-2, Circodiscus amphitrites (Ehrenberg, 1854b); 3-4, Circodiscus biorbiculus n. sp.; 5-14, Circodiscus microporus (Stöhr, 1880); and 15-16, Circodiscus pseudomicroporus n. sp. All are Sg-view at Type1, Fr-view at Type 2. Scale bar equals 0.1 mm. All specimens are from YDY05-01.