Cycladophoridae Suzuki 2019

Family CYCLADOPHORIDAE Suzuki in Sandin, Pillet, Biard, Poirier, Bigeard, Romac, Suzuki & Not, 2019

Cycladophoridae Suzuki in Sandin, Pillet, Biard, Poirier, Bigeard, Romac, Suzuki & Not, 2019: 201-202.

TYPE GENUS. — Cycladophora Ehrenberg, 1846: 385 [type species by subsequent monotypy: Cycladophora ? davisiana Ehrenberg, 1862: 297].

INCLUDED GENERA. — Cycladophora Ehrenberg, 1846: 385 (= Cyclamptidium with the same type species; Diplocyclas synonymized by BjØrklund & De Ruiter 1987: 274; Spuroclathrocycla synonymized by Lombari & Lazarus 1988: 108). —? Valkyria O’Connor, 1997a: 74.

DIAGNOSIS. — Cycladophoridae consist of a helmet-conical shell with two-segments, with or without a frill-like fringe. The cephalis is small, spherical, and may be found pore-less or with relict pores. The thorax is robust and tends to be “well-necked” in its upper part. The thoracic pore frames are generally polygonal-rounded or simply rounded. The width of pore frames is variable in places. Three wing-like rods or rims are visible on upper thoracic wall. The cephalic initial spicular system consists of MB, A-, V-, D-, double l-, double L- and dot-like Ax-rods. A tubular, cephalic horn is absent. Two apical horns emerge from the A-rod, and from the obliquely oriented V-rod. A double Ll-arch develops horizontally and double LV-arch extend at a large angle. The double Dl-arch is of a very small size. Most parts of Ll- and LV-arches are buried in the shell wall whereas the Dl-arch is almost merged with the shell wall to form a tiny clear double hole. The endoplasm is located in the cephalis and upper part of the thorax. No endoplasm is present in the lower half of the test. The occurrence of pseudopodia has not been confirmed as of yet. No algal symbionts are present.

STRATIGRAPHIC OCCURRENCE. — Late Eocene-Living.

REMARKS

The Cycladophoridae differ from the Lithochytrididae by having the latter three distinctive rims or relevant structures related to the V-and double L-rods. The Cycladophoridae are easily distinguished from the Pterocorythoidea by having the latter a cephalic structure with special lobes (pterocorythidtype). The genus composition of the Cycladophoridae results from the molecular phylogeny (Sandin et al. 2019), but the position of Valkyria is problematic. First, the genus Valkyria is a monotypic genus from the Oligocene to the lowest Miocene (O’Connor 1997a: text-fig. 2) and no descendants have been reported. Secondly, Sandin et al. (2019) tentatively identified it as “ Valkyria ?” because the most similar morphotype representative of the genus presented a phylogenetic disconnection with the Valkyria -species. Nevertheless, the cephalic structure of the paratype Valkyria pukapuka (O’Connor 1997a: textfig. 7, pl. 7, figs 11, 12) is identical to that of Cycladophora (Nakaseko & Nishimura 1982: pl. 48, fig. 2; Nishimura & Yamauchi 1984: pl. 36, figs 8a, 8b; Poluzzi 1982: pl. 23, fig. 13; Sugiyama et al. 1992: pl. 21, fig. 3). As repeatedly admitted (Matsuzaki et al. 2015; Sandin et al. 2019), the morphological difference between the Theopiliidae and the Cycladophoridae remains unclear (see remarks in Theopiliidae). A polygonal frame on the thorax and a fragile shell wall are common in Theopiliidae (see remarks in Theopiliidae). The robust shallow-hat shaped nassellarians with polygonal frames were mainly described in the northwestern Pacific and Sea of Japan (e.g., Cycladophora sphaeris (Popova, 1989); Cycladophora urymensis (Popova, 1989); Cycladophora nakasekoi Motoyama, 1996; Cycladophora funakawai Kamikuri, 2010, in published year order). Excepting the difference in polygonal frame, these species share a common structure to Cycladophora. The evolutionary phylogenetic studies, based on species with a continuous stratigraphic record in the aforementioned areas, conclude that Cycladophora davisiana, the type species of Cycladophora, directly evolved from Cycladophora sphaeris (Popova, 1989) (originally Cycladophora sakaii), which in turn is the direct descendant of C. funakawai (Motoyama 1997; Kamikuri 2010). This suggests that a robust skeleton is also a key distinguishing feature for the Cycladophoridae. Other Cycladophoridae taxa are found in these areas and some attempts were made to reconstruct the evolution of the traditional Cycladophoridae which diverged, or evolved, from the Coniforma -form of Anthocyrtis (originally Coniforma; Late Cretaceous), Anthocyrtis (Eocene), the Clathrocyclas -form of Anthocyrtis (end of Eocene to Oligocene), the Spuroclathrocyclas -form of Cycladophora (Spuroclathrocyclas in original; Miocene to Pliocene), and Cycladophora (Pliocene-Pleistocene), respectively (Tochilina & Vasilenko 2015, 2018b). If this reconstruction could be supported at a species level, the Anthocyrtididae would then belong to the same superfam- ily as the Cycladophoridae, or would become synonym of Cycladophoridae. The “Living” appearance of Cycladophora has been well documented (Suzuki & Not 2015: figs 8.10.8, 8.10.9, 8.11.21; Zhang et al. 2018: 19, figs 7.26, 7.27).

VALIDITY OF GENERA

Cycladophora

The type designation for Cycladophora has a complex history because three species, Cycladophora davisiana, Cycladophora stiligera, and Cycladophora tabulata were each selected as the type species in different publications. The genus name was proposed without any assigned species in 1846. The species name was first applied as “ Cycladophora ? davisiana ” by Ehrenberg (1862: 297), but this is not accepted as the first named species of Cycladophora according to the Code (ICZN 1999), article 67.2.5 of which states, “ A nominal species is deemed not to be originally included if it was doubtfully or conditionally includes [...]”. The next applications of Cycladophora were as Cycladophora davisiana and Cycladophora tabulata in Ehrenberg (1873b: 288-289, pl. 2, fig. 11; p. 145, 288- 289, pl. 4, fig. 18 for the latter). Thus, according to ICZN (1999) article 67.2.2, the type species must be selected from Ehrenberg (1873b). Because Ehrenberg had already placed davisiana within Cycladophora, Cycladophora davisiana takes precedence over Cycladophora tabulata as the type species, even if the first application was questionably assigned. Unfortunately, the type specimen of Cycladophora tabulata is missing from the Ehrenberg collection. Thus, Cycladophora tabulata is considered nomen dubium, and the type designation of Cycladophora tabulata by Foreman (1973b: 434) is unlikely. Unaware of the recommendations of ICZN (1926) article 30:III-q, stating that, all else equal, “ show preference to a species which the author of the genus actually studied at or before the time he [sic] proposed the genus,” Campbell (1954: D132) wrongly designated Cycladophora stiligera as the type species of Cycladophora. Cycladophora stiligera was described by Ehrenberg (1874), and therefore cannot be selected as the type species according toICZN (1999) article 67.2.2, which states, “ If a nominal genus [...] was established before 1931 [...] without included nominal species, the nominal species that were first subsequently and expressively included in it are deemed to be the only originally included nominal species.” Thus, Cycladophora davisiana is the only valid type species of Cycladophora. Cyclamptidium has the same type species as Cycladophora. Diplocyclas was previously synonymized with Cycladophora by BjØrklund & De Ruiter (1987: 274). The type species of Spuroclathrocyclas, Clathrocyclas semeles, was placed in Cycladophora by Lombari & Lazarus (1988); thus, Spuroclathrocyclas is potentially a synonym of Cycladophora, although this genus was established in 1989, 1 year later than Lombari & Lazarus (1988). Therefore, the taxonomic characters of Spuroclathrocyclas require evaluation.

Spuroclathrocyclas was defined by Popova (1989: 72), translated as “ Three-segmented shell with an aperture with peristome. First segment spherical and well differentiated, with two apical cylindrical or side horns as external extensions of the A- and V-rods. On the opposite side to the first and second horns is another horn formed by external extension of the single internal rod, which is rarely preserved.Second segment sometimes designated as a pedestal, sub-cylindrical, slightly wider than the first segment.Third segment bell-shaped. First segment smooth, not separated from the second (pedestal) by a constriction. Sharp constriction with an internal septum between the second and third segments. Third segment swollen. Aperture slightly constricted or as wide as the widest part of the last segment. Inner peristome sometimes bearing apophyses of considerable length. Pores are medium on the first and second segments, and wider and quincuncially distributed on the third segment. Walls of most segments are uniformly thin. Basal spines have large pores and are not always preserved.” Spuroclathrocyclas differs from Cycladophora davisiana in four ways: bell-shaped abdomen, ambiguous separation between the cephalis and thorax (pedestal), sharp constriction with an internal septum between the thorax and abdomen, and aperture slight constricted. The species best fitting these characters is Spuroclathrocyclas sphaeris, which is a senior synonym of Cycladophora sakaii; however, based on high-resolution biostratigraphy (Motoyama 1997), this species is the direct ancestor of Cycladophora davisiana. Based on this analysis, Cycladophora davisiana and Cycladophora sphaeris should belong to the same genus. Among these genus names, Cycladophora is the oldest.