RHIZOSPHAERIDAE Haeckel, 1882

Suzuki, Noritoshi, Caulet, Jean-Pierre & Dumitrica, Paulian, 2021, A new integrated morpho- and molecular systematic classification of Cenozoic radiolarians (Class Polycystinea) - suprageneric taxonomy and logical nomenclatorial acts, Geodiversitas 43 (15), pp. 405-573 : 462-463

Family RHIZOSPHAERIDAE Haeckel, 1882

sensu Dumitrica (2017b)

Rhizosphaerida Haeckel, 1882: 455 [as a tribe]. — Dunikowski 1882: 188 [as a tribe]. — Haeckel 1887: 209 [as a tribe]. — Schröder 1909: 18 [as a tribe].

Elatommida Haeckel, 1887: 208 [nomen dubium, as a tribe]. — Schröder 1909: 16 [as a rank between subfamily and genus].

Actinosphaerinae Mast, 1910: 40. — Popofsky 1912: 93, 101.

Rhizosphaeridae – Hollande & Enjumet 1960: 69, 95, 106. — Petrushevskaya 1975: 571. — Anderson 1983: 51. — Dumitrica 1984: 99. — Cachon & Cachon 1985: 287 [in Order Centroaxoplastida ]. — De Wever et al. 2001: 201-202 [in Entactinaria ]. — Afanasieva et al. 2005: S278 [in Order Capsulata ]. — Afanasieva & Amon 2006: 117. — Dumitrica 2017b: 471-473 ( sensu emend. ) [in Order Entactinaria ].

Rhizosphaerinae –Petrushevskaya 1979: 107; Petrushevskaya 1986: 127. — Dumitrica 2017b: 478.

TYPE GENUS. — Rhizosphaera Haeckel, 1861b: 840 [type species by subsequent designation ( Campbell 1954: D68): Rhizosphaera leptomita Haeckel, 1861b: 840 ].

INCLUDED GENERA (Cenozoic genera only). — Haliommilla Haeckel, 1887: 226 (= Actinosphaera with the same type species; Elatommura synonymized byDumitrica 2017b: 478). — Heliosoma Haeckel, 1882: 451 (= Heliosomantha with the same type species). — Hexarhizacontium Dumitrica, 2017b: 488. — Rhizosphaera Haeckel, 1861b: 840 . NOMINA DUBIA. — Elatomma , Elatommella , Pityomma .

JUNIOR HOMONYM. — Rhizospongia Hertwig, 1932 nec d’Orbigny, 1852.

DIAGNOSIS. — Shell with one (rarely two to three) spherical cortical shells and a medullary shell. The medullary shell contains a centrally-placed innermost microsphere that is covered by a sponge-like or latticed frame network. The innermost microsphere does not form a discrete shell. Instead, MB, two A-rays (apical rays) and four B-rays (basal rays) are identified on the microsphere. The A-rays are equals or unequals in appearance and are commonly not connected. The B-rays are interconnected by several arches to form part of the outer sponge-like, or latticed, coarse frame network. The network, outside of the innermost microsphere, tends to develop further on the opposite side of the MB rather than on the MB side of the microsphere. The spherical cortical shell is latticed or sponge-like. Regarding the axopodial system of centroaxoplastid-type: the axoplast is located in the center of the shell and the nucleus wraps the axoplast. Bundles of axoneme from the axoplast penetrate through the fine tunnels that are surrounded by the nucleus membrane. The endoplasm is a gray to yellowish orange color and occupies a large portion inside the cortical shell. The axopodia is flexible ( Haliomma capillacea , Rhizosphaera trigonacantha ) or robust and straight ( Rhizosphaera arcadophora ). Algal symbionts are absent in H. capillacea and R. trigonacantha but are scattered throughout the endoplasm in R. arcadophora .

STRATIGRAPHIC OCCURRENCE. — Early Paleocene-Living.

REMARKS

The internal skeletal structure of Haliommilla has been well documented ( Cachon & Cachon 1972b; pl. 11, fig. a; Takahashi 1991: pl. 9, fig. 2; van de Paverd 1995: pl. 14, figs 1, 2, 3; Suzuki et al. 2009a: figs 1.3, 1.6; Dumitrica 2017b: pl. 3, figs 3-6; pl. 4, figs 1-7), Hexarhizacontium ( Dumitrica 2017b: pl. 9, figs 1-6), and Rhizosphaera ( Dumitrica 1973a: pl. 7, fig. 4; 2017b: pl. 4, figs 8, 9; pl. 5, figs 1-4; pl. 6, figs 1-3; pl. 7, figs 1-12; pl. 8, figs 1-14; Nakaseko & Nishimura 1982: pl. 9, figs 2, 3; Sugiyama & Furutani 1992: pl. 15, figs 8-10?). Major living members of Rhizosphaera in the modern taxonomy are Rhizosphaera banzare ( Riedel, 1958) (= so-called Actinomma antarctica Haeckel, 1887 , an unillustrated species), Rhizosphaera mediana ( Nigrini, 1967) and Rhizosphaera aracadophora ( Haeckel, 1887) . These species were referred by Nigrini (1967: 26) to the genus in order to expand the definition of Actinomma to include a medullary meshwork. This idea was eventually discarded by both anatomical ( Dumitrica 2017b) and molecular phylogenic studies ( Sandin et al. 2021). It is generally difficult to identify living cells with protoplasm as their important skeletal characteristics are hidden within the protoplasm, but this is not the case for Haliommilla and Rhizosphaera . Abundant Haliommilla and Rhizosphaera specimens are easily collected in plankton samplings and the relationships between the protoplasm and the skeleton has been easily observed. Protoplasmic structures of Haliomma and Rhizosphaera were already illustrated in the 1870s for Haliommilla ( Hertwig 1879: pl. 4, figs 1, 3). The fatal symbiosis ( Hertwig 1932: pls 3-5), axopodial system ( Hollande & Enjumet 1954: fig. c; 1960: pl. 5, figs 1-8), and ultrafine protoplasmic structure ( Cachon & Cachon 1972b; Anderson 1984: fig. 8) were studied. Images of living specimens and protoplasm were captured for Haliommilla ( Suzuki et al. 2009a: figs 1.1, 1.4, 1.8; Matsuoka 2017: figs 5.1, 5.2) and Rhizosphaera ( Anderson 1984: fig.8; 1994: fig.4; Suzuki 2005 : pl. 1, figs 1-8;Matsuoka 2017: fig. 4.2; Matsuoka et al. 2017: appendix A). Fine protoplasmic structure was also illustrated in Haliommilla ( Hollande & Enjumet 1960: pl. 5, figs 4, 6; pl. 20, fig. 1; pl. 34, fig. 2; pl. 52, figs 1, 2) and Rhizosphaera ( Hollande & Enjumet 1960: pl. 5, figs 1-3, 5, 7, 8; pl. 24, fig. 1; pl. 34, fig. 1; pl. 49, figs 1-4; pl. 50, figs 1-5; pl. 51, figs 1-3; pl. 59, fig. 1). Protoplasm and algal symbionts were documented by epi-fluorescent observation with DAPI dyeing in Haliommilla ( Suzuki et al. 2009b: figs 3K, 3L; Zhang et al. 2018: 17, fig. 3) and Rhizosphaera ( Ogane et al. 2009c: fig. 3A-3D; 2010: figs 1.1-1.2, 2.1-2.2; 2014; pl. 1, figs 3-4; Zhang et al. 2018: 11, fig. 28). Haliommilla is infected by the syndinean dinoflagellate genus Euduboscquella ( Suzuki et al. 2009b; Bachvaroff et al. 2012). According to Cachon (1964), “ Actinosphaera ” is infected by Hollandella piriformis , but it is impossible to amend the taxonomic name of the host without a complete image.

VALIDITY OF GENERA

Haliommilla

Actinosphaera has the same type species as Haliommilla . It is noted that the description of the internal structure in Haliom-

milla and Elatommura by Campbell (1954: D62) is already outdated. Haliommilla is marked by radial spines covering whole surface ( Campbell 1954: D62) whereas Elatommura is by an outer shell covered by branched radial spines ( Campbell 1954: D62). This difference is not necessary to use for genus classification. These two genera were simultaneously published in Haeckel (1887: 236 for Haliommilla and 242 for Elatommura ). As the real Haliomma capillaceum specimen examined by Haeckel himself, the type species of Haliommilla , was found in the Enrst-Haeckel Haus, Jena, Germany ( Sakai et al. 2009: pl. 23, fig. 4a), Haliommilla is selected as a valid genus.