LARCOSPIRIDAE 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 : 451-452

Family LARCOSPIRIDAE Haeckel, 1887 n. stat.

Larcospirida Haeckel, 1887: 691, 695 [as a subfamily]. — Schröder 1909: 57 [as a subfamily].

Soreumida Haeckel, 1882: 464 [nomen dubium, as a subfamily]; 1887: 604, 712 [as a family]. — Schröder 1909: 4, 62 [as a family]. — Anderson 1983: 25 [as a family].

Streblacanthida Haeckel, 1887: 704 [as a subfamily]. — Schröder 1909: 60 [as a subfamily].

Streblopylida Haeckel, 1887: 704 [as a subfamily]. — Schröder 1909: 60 [as a subfamily].

Larcopylida Dreyer, 1889: 48 [as a family].

Soreumatidae – Poche 1913: 210 [nomen dubium]. — Campbell 1954: D100. — Blueford 1988: 254.

Larcopylidae – Poche 1913: 210. — Chen & Tan 1996: 152. — Tan 1998: 247. — Tan & Chen 1999: 239. — Chen et al. 2017: 149.

Soreumidae [sic] – Clark & Campbell 1942: 51 [nomen dubium] (= Soreumatidae); 1945: 28. — Chediya 1959: 161. — Tan & Tchang 1976: 267.

Larcopylinae – Campbell 1954: D96.

Larcospirinae – Campbell 1954: D100. — Chediya 1959: 159. — Tan & Tchang 1976: 264. — Tan 1998: 280. — Tan & Chen 1999: 265. Streblopylinae – Campbell 1954: D100.

Tholospira [sic] – Tochilina 1985: 98 (= Tholospiridae).

TYPE GENUS. — Larcospira Haeckel, 1887: 695 [type species by subsequent designation ( Campbell 1954: D100): Larcospira quadrangula Haeckel, 1887: 696 ].

INCLUDED GENERA. — Larcospira Haeckel, 1887: 695 (= Larcospirema with the same type species). — Pylospira Haeckel, 1887: 697 (= Pylospirema with the same type species). — Streblacantha Haeckel, 1887: 706 (= Spironetta n. syn., Spironium n. syn., Streblopyle n. syn.). — Tholospira Haeckel, 1887: 699 (= Tholospirema with the same type species; Larcopyle synonymized by Tochilina 1985: 99; Stomatodiscus n. syn.; Tholospironium synonymized by Popofsky 1912: 152).

NOMINA DUBIA. — Drymospira , Larcospironium , Pylospironium , Soreuma , Soreumidium , Soreumium , Sorolarcidium , Sorolarcium , Sorolarcus , Spironilla .

DIAGNOSIS. — A Spirally growing skeleton with a medullary shell of Zonariidae type ( Tetrapyle ) consisting of a microsphere, an antapical sagittal arch and two lateral symmetrical arches originating from the apical part of the microsphere and the top of the sagittal arch. Protoplasm is observed in the Larcopyle -form of Tholospira and Larcospira . Protoplasm fills the shell except but not the outermost peripheral region. Algal symbionts in Larcopyle -form of Tholospira are scattered inside the cortical shell.

STRATIGRAPHIC OCCURRENCE. — late Middle Eocene-Living.

REMARKS

The internal skeletal structure for Larcopyle -form of Tholospira was already documented ( Dumitrica 1989: pl. 15, figs 2, 3; Yamauchi 1986: pl. 1, fig. 18) and Larcospira (Sugiyama et al. 1992: pl. 9, fig. 1-5). A “pylome” was detected in the Larcopyle - and Stomatodiscus -forms of Tholospira , but it consists of a simple aperture without discrete margins (Barwicz-Piskorz 1999: figs 3.H-3J). There is often misidentification of the “ Spireuma ” form of Lithelius (Litheliidae) and Tholospira (Larcospiridae) due to their similar spiral appearance, but the Litheliidae are fundamentally different from the Larcospiridae as the former bear a spherical microsphere and do not have S1a-girdle, G1 and G2, girdle structures. Protoplasm and algal symbionts were documented in the Larcopyle -form of Tholospira ( Zhang et al. 2018: 14, fig.11, p. 19, fig. 7) and Larcospira ( Zhang et al. 2018: 11, fig. 20) using DAPI dyeing epi-fluorescent techniques.

VALIDITY OF GENERA

Streblacantha

Spironium has the same type species as Spironetta . The spiral appearance of Spironium has already been proved as an “artificial torsional” appearance of Larcospira by computer simulation (Ogane & Suzuki 2009 : figs 3 and 4), but this doubtless geometric principle did not apply to the Atlas in time. This is the reason why Spironium is synonymized with Streblacantha . The supporting image of Streblopyle for the Atlas is conspecific with that of Pylospira , but this also failed to be fixed in the Atlas due to time limitation.

Tholospira

Identification of “larcopylids” and “lithelids” has been discussed from the anatomical point of views ( Tochilina 1985: 95-101), practical usages ( Lazarus et al. 2005 97-106; Suzuki et al. 2009d: 248-251; Matsuzaki et al. 2015: 29) and intraspecies variations and evolution ( Tochilina & Vasilenko 2018a: fig. 6, pls 10-13). Lazarus et al. (2005) artificially put any larcopylids and lithelids into a single genus Larcopyle and Suzuki et al. (2009d) as the single genus Lithelius . These artificial treatments are not needed any longer because Larcopyle and Lithelius are completely different in their molecular phylogenetic positions ( Ishitani et al. 2012; Sandin et al. 2021) as well as their evolutionary changes ( Tochilina & Vasilenko 2018a). Our Atlas first visualized the detailed internal structure of Tholospira in Nomarski microscopy with the help of OKU Osamu, a professional of optical microscopy (supporting image for Stomatodiscus in the Atlas ). These images are sufficient to recognize the same internal structures among Larcopyle , Stomatodiscus, Tholospira and Tholospironium . Tholospira was defined by simple spiral turns and Tholospironium by double spiral turns ( Campbell 1954: D100), but the real specimen for Tholospira (the supporting image in the Atlas ) looks to have double spiral turns and the topotypical specimen of Tholospironium from the H.M.S. Challenger Station 271 ( Zhang & Suzuki 2017 : figs 17.1, 17.2) looks as a simple spiral turn. Appearance of spiral turns depends on the orientation of the specimens. Stomatodiscus is defined by a disc shape with two openings ( Campbell 1954: D92), but both sides of the shell are open in the young growing stages of them ( Zhang & Suzuki 2017 : figs 18.1-18.22). Zhang & Suzuki (2017) published the first paper to practically synonymize “ Stomatodiscus ” with Tholospira ( Larcopyle in original). Tholospira is the oldest available name among them.