CENTROLONCHIDAE Campbell, 1954

Family CENTROLONCHIDAE Campbell, 1954

Centrolonchinae Campbell, 1954: D60. — Kozur & Mostler 1979: 29 (sensu emend.).

Hexastylida Haeckel, 1882: 450 [nomen dubium, as a tribe]; 1887: 170-171 [as a subfamily]. — Schröder 1909: 8 [as a subfamily].

Hexastylinae – Campbell 1954: D58 [nomen dubium]. — Chediya 1959: 90. — Dieci 1964: 185.

Stigmosphaeridae Hollande & Enjumet, 1960: 68, 86, 89 [nomen dubium]. — Anderson 1983: 49-50. — Cachon & Cachon 1985: 288 [in Order Periaxoplastida].

Hexastylidae – Petrushevskaya 1975: 567 [nomen dubium]; 1979: 104-105. — Dumitrica 1979: 16, 18. — Kozur & Mostler 1981: 12 (sensu emend.); 1982: 402-403 [in Entactinaria]. — Dumitrica 1995: 21. — Amon 2000: 29. — De Wever et al. 2001: 202-203 [in Entactinaria]. — Suzuki H. et al. 2002: 166, 167 [in Spumellaria]. — Afanasieva et al. 2005: S272 [in Entactinaria]. — Afanasieva & Amon 2006: 108. — Chen et al. 2017: 100.

Centrolonchidae – Kozur & Mostler 1979: 27-28 (sensu emend.).

Centrolonchini – Kozur & Mostler 1979: 29 (sensu emend.).

Stigmosphaerini – Kozur & Mostler 1979: 29 [nomen dubium, as a tribe]; 1981: 16 [a tribe].

Stigmosphaerinae – Kozur & Mostler 1981: 16 [nomen dubium]; Kozur & Mostler 1989: 192.

TYPE GENUS. — Centrolonche Popofsky, 1912: 89 [type species by monotypy: Centrolonche hexalonche Popofsky, 1912: 89].

INCLUDED GENERA. — Centrolonche Popofsky, 1912: 89. — Stigmosphaerusa Hollande & Enjumet, 1960: 90. — Stigmostylus Hollande & Enjumet, 1960: 90.

NOMINA DUBIA. — Centracontium, Stigmosphaera.

DIAGNOSIS. — One latticed cortical shell with a few fiber strings which are fused at a point in the center of the cortical shell. The fibers directly join the cortical shell or are attached at some point to other fibers. Radial spines, if present, are very thin and connected to each fiber. Short to long by-spines radiate throughout the pore frame of the cortical shell. Endoplasm of a tiny size is transparent and surrounds the fused point of the previously mentioned fibers. Probable algal symbionts surround the endoplasm inside the cortical shell. The axopodial system classified as periaxoplastid-type. The axoplast is located on one side of the nucleus; the thick bundle of axonemes penetrates through the nucleus to the opposite side of the axoplast and extends outside the capsular wall, becoming an axoflagellum. The fused point of the fibers is attached on the axoplast. Usually, the fused point is placed at the center of the cortical shell (e.g., Stigmostylus) or on the capsular wall (e.g., Stigmosphaerusa).

STRATIGRAPHIC OCCURRENCE. — late Late Miocene-Living.

REMARKS

The taxonomic concept of the so-called Hexastylidae was historically based on Hexastylus phaenaxonius defined by Haeckel, 1887. This type of designation by Campbell (1954: D58) seems to violate the Article 69.3 of the Code. The validation of the type species of Hexastylus involves a complex issue. Hexastylus was first established in Haeckel (1882) without including any particular species. The first species belonging to Hexastylus is Hexastylus primaevus Rüst, 1885, a Mesozoic radiolarian of Hornfels from Csernye (Hungary) and black hornfels from Rigi (Italy). Under the current Code, the species by Rüst (1885) is the first and only nominal species included in Hexastylus, hence this species is the type species by subse- quent monotypy (Article 69.3) regardless the coherence the Mesozoic species with Haeckel’s description for Hexastylus. Campbell (1951: 528) thought the identification of Hexastylus by Rüst (1885) was a mistake, and Campbell (1954: D58) erroneously designated H. phaenaxonius as type species of Hexastylus. The species H. primaevus was illustrated by Rüst (1885) but this is a nomen dubium due to the fact that the distinguishing skeletal structure are invisible at the generic level. Hence, the “ nomen dubium ” status can only be fixed after Rüst’s drawing because the name-bearing type specimen was destroyed during the Second World War (Steiger 1995). Unfortunately, rexamination of topotypical material is not possible because the outcrops in and around the type locality have been deeply buried at the present (Suzuki 1998a). As the concept of the Hexastylidae, based on H. phaenaxonius, concords with the Centrolonchidae and because “Centolonchinae” was once synonymized with the Hexastylidae (De Wever et al. 2001: 202-203), we replace the valid family name for these members by Centrolonchidae. The internal skeletal structure of Stigmosphaerusa was documented in Helmcke & Bach (1990: 104) and Takahashi (1991: pl. 9, fig. 1). The protoplasm for Centrolonche was illustrated (Zhang et al. 2018: 11, fig. 19). The fine protoplasmic structures were documented for Centrolonche (Hollande & Enjumet 1960: pl. 2, fig. 10), Stigmosphaerusa (Hollande & Enjumet 1960: pl. 1, fig. 11; pl. 43, fig. 2) and Stigmostylus (Hollande & Enjumet 1960: pl. 2, figs 1-4; pl. 31, fig. 8). Hollande & Enjumet (1960) detailed the homogeny of cellular microstructures between Ethmosphaeridae (originally “ Macrosphaeridae ”) and Centrocubidae, and subsequently proposed the “Anaxoplastidies” as an informal group. Later, the Centrocubidae was included into another informal group: the “Cryptoaxoplasides” by Cachon & Cachon (1972c).