Sphaerolarnacillium, 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 : 47

Genus SPHAEROLARNACILLIUM n. gen.

zoobank.org/ 5545813D-C45D-4204-985E-D317AE437220

Type species. Sphaerolarnacillium cochleatum n. gen. et n. sp.

Etymology. Derived from a spherical genus belonging to the family Larnacillidae . The grammatical neuter.

Description. Test consists of a larnacillid central combination and several spherical pseudo-concentric shells. Radial spines may be present or absent. The larnacillid central combination comprises a heteropolar S1a (microsphere) with a 1st twin girdle that develops on both sides of the S1a along the Lt-axis. A rod extends from each side of the S1a along the Lt-axis. The 1st pseudo-concentric shell has two gates with apertures visible in the Sg-view. The 2nd and subsequent pseudo-concentric shells are composed of spirally turned girdles or resemble spherical lattice shells with several apertures. These apertures are relevant to pyloniid gates ( Table 1). These pseudo-concentric shells are connected to each other by several pillar beams. Radial spines, if present, arise from pseudo-concentric shells. Gates of this genus cannot be attributed to a relationship with the girdle; these gates are thus named “para-gates.” Para-gates occasionally close with normal latticed pore frames when a later pseudo-concentric shell develops.

Remarks. Morphotypes with spiral structures have been ascribed to the genera Lithelius ( Litheliidae, Lithelioidea ), Larcopyle ( Pyloniidae, Pylonioidea ), Sphaeropylolena n. gen. ( Pyloniidae, Pylonioidea ), and this genus. Lithelius differs from Sphaerolarnacillium n. gen. based on the presence of a spherical actinommid microsphere. Larcopyle has a small pyloniid central combination and an ellipsoid test, and Sphaeropylolena n. gen. has a pylodiscid central structure. This genus should be carefully differentiated from Sphaeropylolena n. gen. by examining ontogenetic growth series as well as differently oriented specimens in slides because the internal structure appears to have a triangular pattern in obliquely oriented Sphaerolarnacillium specimens. Sphaerolarnacillium n. gen. differs from Larnacalpis Haeckel, 1887 (type species: Larnacalpis lentellipsis Haeckel, 1887 , designated by Frizzell and Middour, 1951), based on the latter’s presence of a completely closed 2nd pseudo-concentric shell and the absence of subsequent girdles.