SPONGODRYMIDAE Haeckel, 1887

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 : 465

Family SPONGODRYMIDAE Haeckel, 1887 n. stat.

Spongodrymida Haeckel, 1887:209 [as a tribe]. — Schröder 1909: 17 [as a tribe].

Tetrasphaeria Haeckel, 1882: 453 [as a subfamily, nomen nudum].

Plegmosphaerida Haeckel, 1882: 455 [nomen dubium, as a tribe]; 1887: 60, 86 [as a subfamily]. — Schröder 1909: 6 [as a subfamily].

Tetrasphaeridae – Enriques 1932: 987.

Plegmosphaerinae – Campbell & Clark 1944a: 10 [nomen dubium]. — Campbell 1954: D50. — Chediya 1959: 72. — Hollande & Enjumet 1960: 68, 102. — Tan & Tchang 1976: 225. — Petrushevskaya 1979: 109. — Cachon & Cachon 1985: 287. — Tan 1998: 101. — Tan & Chen 1999: 128.

Spongodryminae – Hollande & Enjumet 1960: 104. — Anderson 1983: 50-51, 57, 170. — Cachon & Cachon 1985: 287.

TYPE GENUS. — Spongodrymus Haeckel, 1882: 455 [type species by subsequent designation ( Campbell 1954: D96): Spongodrymus elaphococcus Haeckel, 1887: 272 ].

INCLUDED GENERA. — Plegmosphaeromma Haeckel, 1887: 89 . — Spongodictyum Haeckel, 1862: 459 (= Spongodictyoma with the same type species). — Spongodrymus Haeckel, 1882: 455 . —? Tetrasphaera Popofsky, 1912: 111 . —? Tricorporisphaera O’Connor, 1999: 4.

INVALID NAME. — Spongodictyon .

NOMINA DUBIA. — Dictyoplegma, Dictyosphagma, Dispongia, Plegmosphaera , Plegmosphaerantha , Plegmosphaerella , Plegmosphaerusa , Spongiommella , Spongothamnus , Styptosphaera .

JUNIOR HOMONYM. — Dictyosoma Müller 1856 (= Dictyoplegma) nec Temminck & Schlegel, 1845.

DIAGNOSIS. — Spherical spongy cortical shell with a variable number of medullary shells, a very delicately framed central structure and no robust three-bladed radial beams are present.

A brownish to reddish brown opaque endoplasm occupies almost all shells, excluding the peripheral parts of the skeleton. The capsular wall is well visible. An ectoplasmic membrane covers all skeletons including by-spines. No algal symbionts are observed. Axopodial system of centroaxoplastid-type: axoplast placed in the center of the intracapsular zone as a very small fused point and no significant bundles of axoneme. Instead of bundles, axoneme radiate evenly throughout the intracapsular zone. Nucleus is placed in the center of the intracapsular zone and enclosing the axoplast.

STRATIGRAPHIC OCCURRENCE. — Middle Pleistocene-Living.

REMARKS

The number of medullary shells is varied among the genera belonging to Spongodrymidae and the central structure is unstable in several genera. Spongodrymus species at least have a single framed microsphere with fibrous radial beams radiating from the microsphere.Both Spongodictyum and Tricorporisphaera seem to possess latticed double medullary shells. Tetrasphaera has three concentric medullary shells and always co-occurs with Plegmosphaeromma in a same sample. Tricorporisphaera has mildly bladed radial beams arising from the medullary shell.In contrast, both Spongodictyum and Tetrasphaera have fibrous radial beams comparable to Spongodrymus . The family “Tetrasphaeria” was proposed by Haeckel (1882), prior to the establishment of the tribe “Spongodrymida” by Haeckel (1887) himself. The genus Tetrasphaera was first established byPopofsky (1912), and subsequently Haeckel’s family “Tetrasphaeria” became nomen nudum.

The internal skeletal structure was illustrated for the “ Plegmosphaerusa ”-form of Plegmosphaeromma ( Nakaseko & Nishimura 1982: pl. 10, fig. 1) and the “ Styptosphaera ”- form of Plegmosphaeromma ( Suzuki 1998b : pl. 3, fig. 1). The fine protoplasmic structure was illustrated for the “ Plegmosphaerella ”- form of Plegmosphaeromma ( Swanberg et al. 1990; pl. 3, figs 1-6), Plegmosphaeromma ( Hollande & Enjumet 1960: pl. 7, figs 7-9; pl. 8, figs 1-9; pl. 10, figs 1-8; pl. 48, figs 1-5) and Spongodrymus ( Hollande & Enjumet 1960: pl. 7, fig. 3). An image of living specimens was captured for the “ Plegmosphaerella ”- form of Plegmosphaeromma ( Suzuki & Not 2015: fig. 8.8.) and protoplasm and algal symbionts were documented by epi-fluorescent observation with DAPI dyeing for the Plegmosphaerusa - form of Plegmosphaeromma ( Zhang et al. 2018: 19, fig. 1). According to Cachon (1964), “ Plegmosphaera ” is infected with Hollandella lobata , but it is impossible to amend the taxonomic name for the host without its overall image.

Several papers for living radiolarian studies wrote about “ Spongodrymus sp. (spp.)”, but its identification is doubtful because “ Spongodrymus ” appears as nearly covered by full opaque endoplasm, similar in appearance to Spongosphaeromma and the Elaphococcus -form of Cladococcus (Cladococcidae) . These papers never clarified the key points distinguishing between the above-mentioned genera.