ARTOSTROBIIDAE Riedel, 1967

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 : 480-481

Family ARTOSTROBIIDAE Riedel, 1967

sensu Sugiyama (1998)

Artostrobiidae Riedel, 1967a: 148 ; 1967b: 296; 1971: 657. — Riedel & Sanfilippo 1971: 1599; 1977: 878. — Petrushevskaya & Kozlova 1972: 536. — Foreman 1973a: 431. — Nakaseko et al. 1975: 174. — Petrushevskaya 1975: 585. — Nakaseko & Sugano 1976: 131. — Nigrini 1977: 243. — Dumitrica 1979: 34. — Petrushevskaya 1981: 263-264. — Anderson 1983: 44. — Sanfilippo et al. 1985: 702. — Takemura 1986: 63-64. — Nishimura 1990: 158 ( sensu emend. ). — Takahashi 1991: 127. — Chen & Tan 1996: 154. — Hollis 1997: 57. — O’Connor 1997a: 69 ( sensu emend. ); O’Connor 2001: 4 ( sensu emend. ). — Boltovskoy 1998: 33. — Sugiyama 1998: 234. — Kozlova 1999: 134. — Tan & Chen 1999: 355. — Anderson et al. 2002: 1018. — O’Connor 2000: 198. — De Wever et al. 2001: 255-256. — Tan & Su 2003: 113, 226-227. — Afanasieva et al. 2005: S300. — Afanasieva & Amon 2006: 148-149. — Chen et al. 2017: 234.

Artostrobiinae – Petrushevskaya 1971a: 235-236; 1971b: 985- 986. — Petrushevskaya & Kozlova 1972: 538.

TYPE GENUS. — Artostrobium Haeckel, 1887: 1482 [type species by subsequent designation ( Campbell 1954: D140): Lithocampe aurita Ehrenberg, 1844a: 84 ] = junior subjective synonym of Botryostrobus Haeckel, 1887: 1475 [type species by subsequent designation ( Campbell 1954: D141): Lithostrobus botryocyrtis Haeckel, 1887: 1475 ].

INCLUDED GENERA. — Botryostrobus Haeckel, 1887: 1475 (= Artostrobium synonymized by Caulet 1974: 236). — Buryella Foreman, 1973a: 433 . — Dictyoprora Haeckel, 1887: 1305 (= Streptodelus with the same type species). — Lithamphora Popofsky, 1908: 294 (= Phormostichoartus synonymized Petrushevskaya 1981: 273; Poroamphora synonymized Petrushevskaya 1967: 129). — Plannapus O’Connor, 1997a: 69. — Sertiseria Sugiyama, 1994: 2. — Siphocampe Haeckel, 1882: 438 (= Lithomitra , Lithomitrella , synonymized by Nigrini 1977: 254; Siphocampula n. syn., Tricolocampium n. syn.). — Siphostichartus Nigrini, 1977: 257 . — Spirocyrtis Haeckel, 1882: 438 (= Spirocyrtidium with the same type species). — Theocamptra Haeckel, 1887: 1424 . — Tricolocapsa Haeckel, 1882: 436 (= Tricolocapsula with the same type species; Carpocanarium n. syn.).

INVALID NAME. — Tricolopera .

NOMINA DUBIA. — Chlamidophora, Stylocapsa, Tricolocapsium.

JUNIOR HOMONYM. — Acanthocyrtis Haeckel, 1887 (= Phormostichoartus ) nec Haeckel, 1882.

DIAGNOSIS. — Skeleton having three or more segments with a small cephalis. The dividers between the segments below the thorax are weak or not associated with discrete inner rings. A ventral tube is developed around the collar stricture or at the lower part of the cephalis. Pores are regularly distributed along lateral and/or longitudinal directions. Wings, or other relevant structures are absent. The cephalic initial spicular system consists of MB, A-, V-, D-, double L-, double l- and Ax-rods. The MB is oriented upwards, bundles of very long straight rods (Ax and “extra spines” in the sense of Sugiyama & Anderson 1997b: fig. 2) downwardly directed in some genera. A free A-rod is present in the cephalic cavity and extrudes the cephalic wall as a rod-like apical horn. A free V-rod is present in the center or attached to the bottom of a ventral tube. It may also be ramified near the distal end, attaching itself on the shell wall. Several arches sometimes originate from the V-rod to make a complex structure in the cephalis, but these arches are never visible through the tube. Basal ring with two, four or six collar pores is observed. A double collar pore related to the Ll-arch is always present. In the case of four collar pores being present, another double collar pore related to the VL-arch develops. In the case of six collar pores, the double pore related to the Dl-arch appears as a tiny pore. As the MB is obliquely oriented, the basal ring zigzags along the line of the double L-rod and along the line of the double l-rod. A double pore related with the VL-arch is oriented up to the V-rod side; the double pore enmeshed to the Ll-arch rises up to the D-rod side, and the double pore related to the Dl-arch bends down with the D-rod.

An endoplasm is observed and occupies variable places from the cephalis to the distal end of the shell. A bundle of thick pseudopodia extending from the aperture of the shell in Spirocyrtis is observed. However, this observation is not confirmed for Botryostrobus and Tricolocapsa . The nucleus is encrypted within the cephalic cavity in the case of Spirocyrtis . No algal symbionts are reported in living forms.

STRATIGRAPHIC OCCURRENCE. — Early Toarcian-Living.

REMARKS

The Artostrobiidae were usually included in the Eucyrtidioidea ( Petrushevskaya 1981; De Wever et al. 2001), but both the cytological and cephalic structures are fundamentally different when comparing Spirocyrtis and Eucyrtidium (Eucyrtidiidae) . Thus, they cannot be grouped into the same superfamily ( Sugiyama & Anderson 1997b; Sugiyama 1998). This is supported by molecular phylogeny ( Sandin et al. 2019). With the exception of Dictyoprora , the cephalic initial spicular system has been well illustrated in all genera: Botryostrobus ( Caulet 1974: pl. 10, fig. 1; Poluzzi 1982: pl. 28, fig. 16; Nishimura 1990: fig. 34.1, 34.6; Takahashi 1991: pl. 44, fig. 5; Sugiyama et al. 1992: pl. 28, figs 1-3), Buryella ( O’Connor 2001: pls 3, 4), Lithamphora ( Nishimura 1990: fig. 34.7, 34.9; O’Connor 1997b: pl. 5, fig. 4), Plannapus ( O’Connor 1997a: pl. 6, figs 4, 5), Sertiseria ( Sugiyama 1994: pl. 1, figs 1-3), Siphocampe ( O’Connor 1997b: pl. 4, figs 11, 12; Sugiyama 1998: pl. 4, fig. 7; O’Connor 2000: pl. 3, figs 7, 8, 16-18), Siphostichartus (Sugiyama 1998: pl. 5, fig. 5), Spirocyrtis ( Nishimura & Yamauchi 1984: pl. 40, fig. 11b; Nishimura 1990: fig. 34.12), Theocamptra ( Nishimura 1990: fig. 35.4) and Tricolocapsa ( Caulet 1974: pl. 7, figs 3, 4; Nishimura 1990: figs 35.6-35.9; Sugiyama 1998: pl. 5, fig. 6b). Sugiyama (1998) thought that the schematic illustrations by both Nishimura and O’Connor were imprecise.

The Artostrobiidae are distinguished from the Rhopalosyringiidae by the presence of a ventral tube, the absence of wings or another relevant structure, and by the shell’s more regularly distributed pores.

The evolutionary history of the Artostrobiidae at the genus level follows the lineage from Dictyoprora to Siphocampe , Lithamphora (originally Phormostichoartus ), Siphostichartus , Botryostrobus and Spirocyrtis . This order was established according to the stratigraphic range of species ( Nigrini 1977: text-fig. 2; Caulet 1979: fig. 4). The evolution hypothesis of Buryella at the species level was illustrated by O’Connor (2001: text-fig. 5) but the relationship of the Cretaceous Dictyoprora to Buryella is unknown. No bundle of Ax-rod and extra spines is found in Buryella , Dictyoprora, Plannapus, Sertiseria , Theocamptra and Tricolocapsa . When specimens are treated, it may be difficult to identify them in the case of: a) three tiny spines on the cephalis ( Pterocyrtidium and Tricolocapsa ), b) a partially encrypted cephalis (Plannapus and Carpocanium ), and c) an undulated outline on thorax and subsequent segments ( Botryostrobus and Siphocampe ). The genus Tricolocapsa has an artostrobid-type tube on the cephalis, differentiating it from Pterocyrtidium . The cephalis of Carpocanium is generally flattened and appears to have a very complex structure under light transmitted microscopy. Conversely, the cephalis of Plannapus appears to have a simple structure. The difference between Botryostrobus and Siphocampe has not been resolved as of yet because due to the existence of many intermediate forms between these genera in the Miocene. High variability in undulation of thorax and subsequent segments create classification problems at genus and species level ( Boltovskoy & Vrba 1989).

Protoplasm and living condition were illustrated for Botryostrobus ( Sashida & Kurihara 1999: fig. 11.12; Suzuki & Not 2015: fig. 8.11.12), Spirocyrtis ( Matsuoka 1993b: pl. 5, figs 3, 4; 2007: fig. 4c; 2017: fig. 29; Sugiyama & Anderson 1997b: pl. 1, figs 7, 8; Ogane et al. 2009c: figs 3L-3N; Suzuki et al. 2009b: figs 2E, 2F; Matsuoka et al. 2017: Appendix B; Zhang et al. 2018: 15, figs 4.23) and Tricolocapsa ( Suzuki & Not 2015: fig. 8.11.13). A cytological ultrafine structure was also documented in Spirocyrtis ( Sugiyama & Anderson 1997b: pls 6, 7).

VALIDITY OF GENERA

Siphocampe

Lithomitra has the same type species as Lithomitrella so the latter is automatically synonymized with Siphocampe , following Nigrini (1977: 254). Tricolocampium was placed in the “Stichocorythinae”of the “ Stichocorythidae ” within the “subsuperfamily Triacartilae” sensu Campbell (1954 : D141-142), and then this genus was characterized by a shell divided by many strictures into cephalis, thorax, abdomen, the presence of radial apophyses, an open aperture on the terminal end of the last segment, a hollow cylindrical cephalic tube, similar heights of segments ( Campbell 1954: D136, 140-142). When referred to the real specimens identifiable as Siphocampe tubulosa ( Haeckel 1887: pl. 79, fig. 13), type species of Siphocampula , the description by Campbell (1954) is not precise. This test looks to have many segments but it is due to the repetitions of surface ornaments identical to those of Siphocampe (See support images for Siphocampe and Lithomitrella in the Atlas ). They are also no true dividers inside the test of Siphocampula as shown in the support image for Lithomitra in the Atlas . Tricolocampium was placed in the “Theocorythinae” of the “ Theocorythidae ” in the “subsuperfamily Theopiliilae” sensu Campbell (1954 : D129, 132, 134). The taxa under these higher taxonomic ranks are characterized by a shell divided by two transverse strictures into cephalis, thorax and abdomen, no basal apophyses, and open aperture. Tricolocampium itself is defined by a cylindrical abdomen, no apical horn, and similar pore patterns on thorax and abdomen in Campbell (1954: D134). The description at higher ranks also matches with the type-illustration of Siphocampe ( Haeckel 1887: pl. 79, fig. 10). Campbell (1954) documented similar pore patterns on thorax and abdomen, but this does not correspond to the type-illustration of Tricolocampium . Rather, the pore patterns on thorax and abdomen in the type species of Tricolocampium ( Haeckel 1887: pl. 66, fig. 21) is similar to the type-illustration of Siphocampe . The remaining difference between these two genera is the occurrence, in the definition, of a tube on the cephalis. However, real specimens identifiable as Tricolocampe cylindrica have a tube extending laterally to the cephalis (the support image for Tricolocampium in the Atlas ) and, thus, there is no reason to keep Tricolocampium as valid. The oldest available names are Siphocampe and Lithomitra which were published in the different papers of the same year ( Haeckel 1882 for Siphocampe and Bütschli 1882 for Lithomitra ). As the first reviser, Nigrini (1977: 254) has already validated Siphocampe .

Tricolocapsa

Tricolocapsula has the same type species as Tricolocapsa . Tricolocapsa is defined by the lack of an apical horn, no latticed septum between the thorax and the abdomen and a thorax as large as the abdomen or larger ( Campbell 1954: D136). Carpocanarium is defined by a corona of six feet, no thoracic ribs and a hornless cephalis hidden within the thorax ( Campbell 1954: D127). These descriptions, however, completely mismatch the type-illustrations of both Tricolocapsa ( Haeckel 1887: pl. 66, fig. 1) and Carpocanarium ( Stöhr 1880: pl. 3, fig. 8). First, identical specimens having a perfect third segment have not been so far found. Real specimens most similar to Tricolocapsa theophrasti , the type species of Tricolocapsa , always have a poreless corona with an open aperture instead of a perfect third segment, a very thin tiny horn which is probably lost in most specimens, and no latticed septum between the thorax and the poreless corona (the support image for Tricolocapsa ). The illustration of Carpocanium calycothes in Stöhr (1880), the type species of Carpocanarium , has a perfect spherical cephalis above the thorax, unlike a “cephalis hidden within the thorax” as written in Campbell (1954: D127). The “corona with six feet” mentioned by Campbell (1954) is an obviously wrongly recognized broken peristome if we refer to the type-illustration. The real specimens identical to this species mostly confirm the illustrations of the type. Different characteristics observable in real specimens point out a very tiny apical horn, a tube in the cephalis-thoracic suture, a trace of a thoracic rib, and six undulations on the peristome of the corona instead of six feet. Based on support images for both Tricolocapsa and Carpocanarium , these two specimens obviously should belong to the same genus. Tricolocapsa is the oldest available name among them.