DIMELISSIDAE Petrushevskaya, 1981

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 : 503-504

Family DIMELISSIDAE Petrushevskaya, 1981 n. stat.

sensu Caulet emend. herein

Dimelissinae Petrushevskaya, 1981: 82; 1986: 132. — Afanasieva et al. 2005: S292. — Afanasieva & Amon 2006: 139.

Sethopilida Haeckel, 1882: 431 [nomen dubium, as a tribe]; Haeckel 1887: 1192, 1194, 1195 [as a subfamily].

Spongolarcida Haeckel, 1887: 606, 613 [nomen dubium, as a subfamily]. — Schröder 1909: 52 [as a subfamily].

Sethopilinae [sic] – Clark & Campbell 1942: 65 [nomen dubium] (= Sethopiliinae); Clark & Campbell 1945: 37. — Campbell & Clark 1944a: 41; 1944b: 23. — Chediya 1959: 199. — Tan & Tchang 1976: 274. — Chen et al. 2017: 182.

Spongolarcinae – Campbell 1954: D96 [nomen dubium]. — Chediya 1959: 152.

Sethopiliidae – Campbell 1954: D122 [nomen dubium].

Sethopiliinae – Campbell 1954: D122 [nomen dubium]. — Petrushevskaya 1981: 74-75. — Afanasieva et al. 2005: S292. — Afanasieva & Amon 2006: 139.

TYPE GENUS. — Dimelissa Campbell, 1951: 529 [type species by subsequent designation according toICZN 1999, art. 67.8 ( Campbell 1951: 529): Lithomelissa thoracites Haeckel, 1861b: 836 ] = junior subjective synonym of Peromelissa Haeckel, 1882: 433 [type species by subsequent designation ( Campbell 1954: D124): Peromelissa phalacra Haeckel, 1887: 1236 ].

INCLUDED GENERA. — Arachnocorys Haeckel, 1861b: 837 (= Arachnocoronium with the same type species; Acanthocoronium n. syn.). — Archiperidium Haeckel, 1882: 429 . — Cryptogyrus Sugiyama, 1993: 65. — Lithomelissa Ehrenberg, 1847: 54 (= Acromelissa synonymized by Petrushevskaya 1975: 592). — Peromelissa Haeckel, 1882: 433 (=? Dicorys synonymized by Petrushevskaya 1981: 84;? Micromelissa Haeckel, 1882 nec Haeckel, 1887, Psilomelissa synonymized by Petrushevskaya 1971a: 133; Dimelissa synonymized by Matsuzaki et al. 2015: 44). — Phormacantha JØrgensen 1905: 132 . — Plectacantha JØrgensen, 1905: 131 .

INVALID NAME. — Amphicryphalus.

NOMINA DUBIA. — Acanthocorallium , Acanthocorythium , Acanthocorys, Amphicentria , Amphiplecta , Arachnocorallium , Arachnocorythium , Mitrocalpis , Peridarium , Peridium , Sethomelissa , Sethopilium , Spongolarcus .

JUNIOR HOMONYM. — Micromelissa Haeckel, 1887 (= Dimelissa ) nec Haeckel, 1882.

DIAGNOSIS. — Anatomically, Dimelissidae are two-segmented Plagiacanthoidea with a well-developed first segment (cephalis) and a less developed, sometimes absent, second segment (thorax). The cephalis, mono-chambered, is separated from the thorax and bears well-developed A, V, and double L-rod. No cephalic lobes develop. The cephalic initial spicular system consists of MB, A-, V-, D-, and double L-rods. The double l-rod is generally absent. The MB is very short or degraded at a pointed connection (PC). The PC tends to be located on the apical side of the test. The MB, if present, is located near the apical side. The D- and double L-rods are oriented at an even angle at 180 degrees from PC. The most constricted level (neck) of the shell is always located above the MB’s level. The A-rod merges into the cephalic wall, or may be partly or fully free in the cephalic cavity. Double AL- and double LV-arches are generally present. As both A- and V-rods are oriented upward, both double AL-arches and double LV-arches also rise upward. AL-arches and VL-arches merge with the cephalic wall or are freely located inside the cephalic cavity. However, these arches never form sutures on the cephalic wall. If AL-arches merged with the cephalic wall, they tend to form larger pores than other pores found on the shell. The Ax-rod is present. A basal ring rarely develops in some species and is directly connected with the D- and double L-rods to form three collar pores. In this case, the basal ring is located below the MB’s level.

Protoplasm was observed in Arachnocorys, Cryptogyrus , Peromelissa and Plectacantha . The endoplasm is transparent to yellowish transparent and located within the cephalis (at variable degrees) and at least in the upper part of the thorax. In some species including Arachnocorys , multi nuclei are observed. Algal symbionts are present inside the cephalis of Arachnocorys , but no algal symbionts are found in Cryptogyrus, Peromelissa and Plectacantha .

STRATIGRAPHIC OCCURRENCE. — late Middle Eocene-Living.

REMARKS

Differing from the Pseudodictyophimidae Suzuki , n. fam., the Dimelissidae lack a cephalic structure such as a basal ring. This family can be divided into three groups: In the first instance, the cephalis is well-developed, sometimes with an open upper part and an arachnoid wall ( Arachnocorys , Archiperidium, Cryptogyrus , Phormacantha , Plectacantha ). The cephalis also bears strong extensions of the main rods arising from MB. The thorax is short, considerably reduced, and mostly constituted by extensions of the D- and double L-rods. In the second, the cephalis is globular and closed, with a wall perforated by small circular pores ( Lithomelissa , Peromelissa ). No robust feet are present. A strong horn is inserted mostly laterally. The thorax is more developed, with pores and D- and double L-rods both present. Finally, the third instance included Archiperidium, Cryptogyrus and Phormacantha ). It is extremely difficult to differentiate the Dimelissidae from the Pseudodictyophimidae Suzuki , n. fam. due to an extensive similarity in overall shape.True feet are not developed in Dimelissidae ; however, this character is also observed in some genera of Pseudodictyophimidae Suzuki , n. fam. ( Pseudodictyophimus and Tripodocyrtis ). The most significant difference between the Dimelissidae and the Pseudodictyophimidae Suzuki , n. fam. is the absence of lobes in the cephalis. The Dimelissidae lack cephalic lobes. However, some lobes are absent or poorly developed in several genera of the Pseudodictyophimidae Suzuki , n. fam. ( Steganocubus and Syscioscenium ).

The cephalic internal spicular system of many genera in this family was illustrated but the genus names used must be revised. This revision is necessary due to the complex internal structures, the wrongly recognized type-species, and the use of a genus name that was defined by un-illustrated type species. After our re-examination of the genus position, the cephalic internal spicular system of the following genera has been well illustrated: “ Amphicryphalus ” ( Funakawa 1995a: pl. 1, figs 1-3), “ Amphiplecta ” ( Nishimura 1990: fig.14.6-14.8, 19.4?; Funakawa 1994: figs 6, 7.2-7.3; Nishimura & Yamauchi 1984: pl. 24, fig. 2), Archiperidium ( Nishimura & Yamauchi 1984: pl. 23, figs 1-3), Arachnocorys ( Nishimura & Yamauchi 1984: pl. 24, figs 10, 11; Nishimura 1990: figs 14.1-14.4, 16.2, 16.3?, 16.4?; Takahashi 1991: pl. 26, fig. 6; Sugiyama et al. 1992: pl. 18, fig. 4), Cryptogyrus ( Sugiyama 1993: figs 19.1-19.5, 20.1-20.2), “ Helotholus histricosa ” ( Dumitrica 1973a: pl. 12; Lazarus 1990: pl. 7, figs 1-5; Nishimura & Yamauchi 1984: pl. 24, fig. 9), Lithomelissa ( Nishimura & Yamauchi 1984: pl. 32, fig. 5; Nishimura 1990: figs 15.1, 15.2, 15.4-15.8, 16.1, 16.5?; Takahashi 1991: pl. 26, fig. 3?; Sugiyama et al. 1992: pl. 17, fig. 1; Funakawa 1995b: figs 10.3, 10.4; O’Connor 1999: pl. 2, figs 23-27), “ Peridium ” ( Funakawa 1994: fig. 11.1, 11.2; Nishimura 1990: fig.13.8-13.11; Takahashi 1991: pl.26, fig. 4; Funakawa 1995a: pl. 2, figs 1-4, pl. 3, figs 1-4), Peromelissa ( Nishimura & Yamauchi 1984: pl. 24, fig. 7, pl. 32, fig. 4) and Plectacantha ( Nishimura & Yamauchi 1984: pl. 22, figs 11-13). However, the generic combination of the Dimelissidae has not been supported by any form of objective phylogenetic evidence. Furthermore, molecular phylogenetic studies do not provide a sufficient resolution to resolve this issue, and as of yet, many genera remain undescribed. “Living” or protoplasm image were illustrated for Arachnocorys ( Zhang et al. 2018: 9, figs 23, 24), Cryptogyrus ( Sashida & Kurihara 1999: figs 11.7, 11.16; Suzuki & Aita 2011: fig. 5M; Zhang et al. 2018: 15, fig. 6, p. 19, fig. 18), Peromelissa ( Sashida & Kurihara 1999: figs 11.4, 12.10; Suzuki & Not 2015: fig. 8.11.9; Matsuoka 2017, fig. 21; Zhang et al. 2018: 15, figs 7, 17, 18, p. 21, figs 14-17), and Plectacantha ( Suzuki et al. 2009b: figs 2K, 2L). Lithomelissa may be infected with Marine Alveolata Group I ( Ikenoue et al. 2016).

VALIDITY OF GENERA

Arachnocorys

Arachnocorys is characterized by a shell enveloped by a weblike network ( Campbell 1954: D126), whereas the Acanthocoronium shell is enveloped by a simple network ( Campbell 1954: D125). A web-like network around the cephalis is not always present in Arachnocorys specimens, which indicates intraspecific variation in ontogenetic growth. Arachnocorys is the oldest available name among all synonyms.