Sphaeropylolena, 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 : 38-39

Genus SPHAEROPYLOLENA n. gen.

zoobank.org/ F9753C4-FFFD-412B-AA11-5819E45DB6EB

Type species. Sphaeropylolena laxa n. gen. et n. sp.

Etymology. Latin feminine noun “sphaera” (-ae) and the genus name Pylolena , meaning spherical pylodiscid genera. Grammatical feminine noun.

Description. Test consists of a triangular 1st pseudo-concentric shell with a S1a (microsphere), an inflated triangular 2nd pseudo-concentric shell, and surrounding spherical pseudo-concentric shells, with more than eight (likely up to 12) strong radial beams. The architecture of the first two triangular pseudo-concentric shells is the same as that of the genus Pylodiscus . The 3rd pseudo-concentric shell has rounded corners. Its shape is variable between ellipsoid, inflated pentagonal, and inflated hexagonal shapes, depending on the orientation of the test. The 3rd pseudo-concentric shell comprises six to eight girdles. A joint with three or four girdles forms on a flat side of the 2nd pseudo-concentric shell. The tunnel of each gate is oriented radially from the center of the test. Similar sets of girdles develop on the opposite flat side of the 2nd pseudo-concentric shell. These two sets of girdles from both flat sides are connected by the opposite sides of other girdles with visible apertures. These girdles resemble circular bands or several jointed girdles and will then form the 3rd pseudo-concentric shell. In some case, girdles of the 3rd pseudo-concentric shell are spirally turned to form different shapes, similar to the 2nd pseudo-concentric shell. The 3rd pseudo-concentric shell possesses several apertures relevant to gates, but the orientations of these gates are irregular relative to the encircling direction of each girdle. Radial spines may or may not be present; if present, several spines emerge from the edge of the girdles of the 2nd pseudo-concentric shell, and two more spines connect to the girdles of the 2nd pseudo-concentric shell. Pores are circular to subcircular in the central combination and subcircular to elliptical in the 1st pseudo-concentric shell.

Remarks. The overall appearance of Sphaeropylolena is similar to that of Pentapylonium Dumitrica, 1991 a ( Dactyliosphaeridae, Pylonioidea ; type species Pentapylonium implicatum Dumitrica, 1991 a ), but the internal structure is different. The genus Sphaeropylolena n. gen. is similar to the genus Discozonium Haeckel, 1887 , but the original description of the latter described a “ pylodiscid with Triopyle -shaped medullary shell and Pylodiscus - shaped cortical shell, which is surrounded by an equatorial chambered girdle ” ( Haeckel, 1887, p. 571). Sphaeropylolena n. gen. does not have an “equatorial chambered girdle”; it has a Pylodiscus - type central combination and two pseudo-concentric shells. Therefore, juvenile forms of these two genera may not be differentiable from Pylodiscus , although Sphaeropylolena n. gen. with a 3rd pseudo-concentric shell is easily distinguished from Pylodiscus based on the former’s spherical appearance. This new genus also includes “ Streblacantha ” circumtexta ( JØrgensen, 1899), based on the photographs of its lectotype and paralectotypes ( Dolven et al., 2014, plate 3, figures 1a-5b). This species was first described as a member of the genus Sorolarcus Haeckel, 1887 , and later moved to Streblacantha Haeckel, 1887 , by JØrgensen (1905). The lectotype and paralectotype photographs of this species from Dolven et al. (2014) show slightly oblique Sg-views in plate 3 and figures 1a and 4a, oblique basal area from the Pl-view in plate 3 and figure 3, and the oblique apical area from the Pl-view in plate 3 and figure 5a. Taking their orientations into account, the skeletal structures of these type specimens of “ Streblacantha” circumtexta show pylodiscid internal structure and several spirally developed girdles. Plate 3 and figure 4b of Dolven et al. (2014) show the typical three apertures of the 1st pseudo-concentric shells

PALAEO- ELECTRONICA.ORG of Sphaeropylolena n. gen. Although JØrgensen (1905) documented that a specimen with “a single central chamber” would “not belong to the genus Sorolarcus ”, “ Streblacantha ” circumtexta belongs to the family Pyloniidae . The type species of Streblacantha , Streblacantha siderolina Haeckel, 1887 , appears to have a spherical S1a without any girdles, and thus “ Streblacantha ” circumtexta does not belong to Streblacantha . The type species of Sorolarcus , Sorolarcus larnacillifer Haeckel, 1887 , appears to have the typical pyloniid central structure, but has spirally arranged chambers, and thus “ Streblacantha ” circumtextum does not belong to Sorolarcus .