Larcospira teres, 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 : 23-25

Larcospira teres n. sp.

Figure 13

zoobank.org/ CE058DC9-B18D-4884-9009-35692F668CD2

1970 Larcospira quadrangula Haeckel ; Nigrini, p. 169, pl. 2, fig. 9.

1976 Larcospira quadrangula Haeckel ; Tan and Tchang, p. 264-265, text-fig. 36.

1977 Larcospira quadrangula Haeckel ; Kling, p. 217, pl. 2, fig. 18.

1978 Larcospyra quadrangula Haeckel (wrong spelling for the genus name); McMillen and Casey, pl. 3, fig. 18.

1979 Larcospira quadrangula Haeckel ; Nigrini and Moore, p. S133-134, pl. 17, fig. 2.

1980 Larcospira quadrangula Haeckel ; Johnson, and Nigrini, p. 127, text-fig. 9a, pl. 2, fig. 15.

1981 Larcospira quadrangula Haeckel ; Takahashi and Honjo, p. 150, pl. 6, fig. 2.

1984b Larcospira quadrangula Haeckel ; Nishimura and Yamauchi, p. 41, pl. 17, fig. 11, pl. 43, fig. 12.

1985 Larcospira quadrangula Haeckel ; Boltovskoy and Jankilevich, pl. 3, fig. 15.

1985 Larcospira quadrangula Haeckel ; Morley, p. 410, pl. 3, fig. 9.

1986 Larcospira quadrangular Haeckel (wrong spelling for the species name); Morley and Kohl, pl. 1, fig. 9.

1986 Larcospira quadrangula Haeckel ; Yamauchi, pl. 1, fig. 17.

1987 Larcospira quadrangula Haeckel ; BjØrklund and de Ruiter, fig. 2.18.

1987 Larcospira quadrangula Haeckel ; Dworetzky and Morley, pl. 2, fig. 9.

1990 Larcospira quadrangula Haeckel ; Yeh and Cheng, pl. 6, fig. 7.

1991 Larcospira quadrangula Haeckel ; Takahashi, p. 92, pl. 23, figs. 11-12.

1995 Larcospira quadrangula Haeckel ; van de Paverd, p. 188-190, pl. 55, figs. 1-2, 4-5.

1996 Larcospira quadrangula Haeckel ; Chen and Tan, p. 198, pl. 23, figs. 1-3, pl. 46, figs. 2, 3.

? 1996 Larcospira quadrangula Haeckel ; Haslett, pl. 1, fig. 1.

1998 Larcospira quadrangula Haeckel ; Tan, p. 280-281, text-fig. 270.

1999 Larcospira quadrangula Haeckel ; Tan and Chen, p. 265-266, text-fig. 5.182.

2008 Larcospira quadrangula Haeckel ; Kamikuri, Motoyama, and Nishimura, pl. 3, fig. 13.

2015a Phorticium pylonium Haeckel group; Matsuzaki, Suzuki, and Nishi, p. 32, fig. 6.11 (only).

Etymology. The Latin adjective “teres ” (-retis),

meaning smoothly rounded.

Holotype. Specimen in Figure 13.1-2 from the sample YDY05-01.

Paratype. Specimen in Figure 13.6-7 from the sample YDY05-01.

ZHANG & SUZUKI: TAXONOMY OF HOLOCENE PYLONIOID

Description. Test is oval in shape, and consists of a spindle-like central part and smooth, latticed girdles. The length ratio of the Sg-axis to the coiling axis (the Lt-axis) is 0.9–1.1. The 2nd pseudo-concentric shell is characterized by twin outermost girdles connected with the opposite ends of the 1st pseudo-concentric shell along the Lt-axis. Both ends of the 3rd pseudo-concentric shell along the Lt axis are depressed. Several pillar beams connecting an inner girdle to the outer girdle are bifurcated distally. These pillar beams are thin or poorly developed, and therefore do not to create any major convex depressions on the 3rd pseudo-concentric shell; the 3rd pseudo-concentric shell therefore has a smooth surface. The width ratio of the 3rd pseudo-concentric shell to the 2nd pseudo-concentric shell is 2.7–3.2. Rarely, radial spines develop somewhat on the surface of the 3rd pseudo-concentric shell. Pores are small on the central combination and the S1a-girdles. They are large and rounded polygonal in shape with fine pore frames on the 2nd and outer pseudo-concentric shells.

Remarks. All specimens of “ Larcospira quadrangula ” with smooth 3rd pseudo-concentric shells illustrated in previous papers (see the synonym list) are identified as this new species. Larcospira teres n. sp. differs from L. quadrangula based on the smooth surface of former’s 3rd pseudo-concentric shell with thin pillar beams. The width ratio of the 3rd pseudo-concentric shell to the 2nd pseudo-concentric shell is larger in L. teres n. sp. (2.7–3.2 in L. teres n. sp. vs. 2.5–2.7 in L. quadrangula ). All fossil “ L. quadrangula ” specimens older than Pliocene in age illustrated in previous papers (Nigrini and Lombari, 1985; Levyikina, 1986; Sugiyama et al., 1992) have spiral girdles with smooth surfaces like those of L. teres n sp. However, these fossil specimens differ from the representative species in that they have narrow outermost spiral girdles and that both ends of the test are acute. Therefore, these fossil species are considered to belong to an undescribed species.

Dimensions. Based on the holotype specimen. The length and width of pseudo-concentric shell: 27.2 μm and 12.2 μm (1st pseudo-conentric shell), 66.7 μm and 46.5 μm (2nd pseudo-concentric shell), and 139.5 μm and 150.8 μm (3rd pseudo-concentric shell). The ratio of the length to the width: 2.2 (1st pseudo-conentric shell), 1.4 (2nd pseudo-conentric shell), and 0.9 (3rd pseudo-concentric shell). The width ratio of the 3rd pseudo-concentric shell to the 2nd pseudo-concentric shell is ca. 3.2. The width ratio of the 2rd pseudo-concentric shell to the 1st pseudo-concentric shell is ca. 3.8.

Figures

FIGURE 13. Photographs of the encountered morphotypes of Larcospira teres n. sp. All are Pl-view at Type 1. Scale bar equals 0.1 mm. All specimens are from YDY05-01.