Sethoperida Haeckel, 1882: 433 [as a tribe]; 1887: 1192, 1194, 1232 [as a subfamily].
Archicorida Haeckel, 1882: 427 [nomen dubium, as a tribe]; 1887: 1133, 1179, 1180 [as a subfamily]. — Wisniowski 1889: 687.
Callimitrida Haeckel, 1882: 431 [below tribe].
Sethophatnida Haeckel, 1882: 433 [as a tribe].
Sethophaenida – Haeckel 1887: 1192, 1242, 1285 [nomen dubium, as a subfamily].
Tripocyrtida Haeckel, 1887: 1192-1194 [as a family]. — Bütschli 1889: 1986 [as a family]. — nec Rüst 1892: 181 [as a family]. — nec Cayeux 1894: 212.
Tripocyrtidae – Haecker 1908: 448. — Popofsky 1908: 274; 1913: 333. — Schröder 1914: 100. — Wailes 1937: 13. — Clark & Camp- bell 1942: 65; 1945: 37. — Campbell & Clark 1944a: 41; 1944b: 23. — Chediya 1959: 199. — Tan & Tchang 1976: 274. — Tan & Su 1982: 169; 2003: 113. — Chen & Tan 1996: 153. — Tan & Chen 1999: 296. — Chen et al. 2017: 182.
Sethoperinae – Haecker 1908: 448-451. — Campbell 1954: D124. — Chediya 1959: 203. — Petrushevskaya 1971a: 76-80; 1971b: 989-990 (sensu emend.); 1981: 295. — Tan & Tchang 1976: 279. — Afanasieva et al. 2005: S293. — Afanasieva & Amon 2006: 140. — Chen et al. 2017: 198.
Archicorinae – Clark & Campbell 1942: 65 [nomen dubium]; 1945: 35. — Campbell & Clark 1944a: 40; 1944b: 22. — Chediya 1959: 196.
Sethoperidae – Petrushevskaya & Kozlova 1972: 535 (sensu emend.); Petrushevskaya 1975: 589; 1981: 291-295. — Dumitrica 1979: 30. — Takahashi 1991: 98. — De Wever et al. 2001: 236, 238. — Afanasieva et al. 2005: S293. — Afanasieva & Amon 2006: 140.
Tripocyrtididae – Poche 1913: 220.
Sethophatninae – Campbell 1954: D128 [nomen dubium].
Sethophaeninae – Chediya 1959: 208 [nomen dubium].
Sethophatnidae – Loeblich & Tappan 1961: 228 [nomen dubium].
TYPE GENUS. — Sethopera Haeckel, 1882: 433 [type species by subsequent designation (Campbell 1954: D124): Sethopera tricostata Haeckel, 1887: 1232] = junior subjective synonym of Clathrocanium Ehrenberg, 1861b: 829 [type species by subsequent designation (Campbell 1954: D122): Clathrocanium squarrosum Ehrenberg, 1873a: 303].
INCLUDED GENERA. — Callimitra Haeckel, 1882: 431 (= Arachnothauma n. syn.). — Clathrocanium Ehrenberg, 1861b: 829 (= Clathrocanidium with the same type species; Arachnopilium, Clathrocorona, Clathrolychnus synonymized byPetrushevskaya 1971a: 80; Tripocyrtis synonymized by Petrushevskaya 1981: 300; Sethopera n. syn.). — Clathrocorys Haeckel, 1882: 431. — Dictyocodoma Haeckel, 1887: 1335. — Dictyocodon Haeckel, 1882: 435 (= Dictyocodella with the same type species). — Pteropilium Haeckel, 1882: 435 (= Clathropilium with the same type species).
INVALID NAME. — Sethophaena.
NOMINA DUBIA. — Archibursa, Archicorys, Sethophatna.
DIAGNOSIS. — Sethoperidae consist of a one- to two- segmented, rounded pyramidal shell with one long apical horn and three long feet (or wings). The cephalis is latticed. A wired screen develops between the apical horn and each of the feet, (or wings) and/or between the feet (or wings) and thorax. The thorax varies from a three-sided, rounded pyramid to a basket-like from. The cephalic initial spicular system consists of MB, A-, V-, D-, and the double-L rods. Double l-rod absent. The basal ring is directly connected to the D- and double L-rods forming three collar pores. Several arches develop freely in the cephalic cavity, or are attached on the inner side of the cephalic wall. However, but these do not form sutures on the cephalic wall. The combination and connecting ends of the arches such as AD-arch, ap -arch (one of AL-arch), ac -arch (one of AD-arch) and pj -arch (one of VL-arch) are variable. A straight double a -spinule extends laterally as a part of the ap -arch, a second double arch named the m -(ap) arch, may develop between the m -position on the A-rod and the ap -arch. A further second double arch may be present between the g -position of the A-rod and the m -(ap) arch. The V-rod is present but never protrudes through the cephalic wall. In its place, a very small ventral tube exists.
The protoplasm is observed in Callimitra and Clathrocanium. The endoplasm with multi-nuclei or a single nucleus is very small, transparent, and located in the cephalic cavity. Several algal symbionts are located inside and/or just below the cephalis.
STRATIGRAPHIC OCCURRENCE. — Late Eocene-Living.
REMARKS
The taxonomic position of the Sethoperidae at the superfamily and lineage levels, as well as the taxonomic differences between the Phaenocalpididae and Sethoperidae require additional studies. Tripocyrtis appear to be a synonym of Periplecta (Phaenocalpididae) while Dictyocodoma and Clathropilium appear to be members of the Stichopiliidae and Ceratocyrtidae, respectively. In most cases, the Sethoperidae are distinguished from the Phaenocalpididae by the presence of a wired screen in the cephalis and thorax. However, in some critical cases, a detailed examination of the cephalic initial spicular system is necessary (Tripocyrtis vs Periplecta). The cephalic initial spicular system of the Phaenocalpididae is broadly similar to that of the Sethoperidae. The differences between the Sethoperidae and the Phaenocalpididae are: 1) the development a second arch along D- and double L-rods outside of the basal ring in Sethoperidae; 2) the lack of developed sutures on the cephalis with cephalic arches in Sethoperidae; and 3) the presence of a straight a-spinule and arches that are related to m- and g-positions on the A-rod forming a “segmented” appearance inside the cephalis from dorsal or ventral view in Sethoperidae. The type-illustration of Dictyocodoma is probably obtained from the dorsal or ventral view of Stichopiliidae. This view allows the user to find a single apical horn if the supporting image is indeed correct. However, this observation is structurally impossible as the view with the three wings should be also associated with the identification of both apical and ventral horns. A Pteropilium species was previously identified as a member of Lipmanella (Nishimura & Yamauchi 1984: pl. 34, fig. 7). However, if the cephalic initial spicular system defined by Funakawa (2000) is considered, Pteropilium is completely different from Lipmanella.
The cephalic initial spicular system has been well illustrated for Callimitra (Nishimura 1990: figs 22.3, 22.4; Takahashi 1991: pl. 27, fig. 3), Clathrocanium (Poluzzi 1982: pl. 29, figs 1-3; Takahashi 1991: pl. 26, figs 12; Sugiyama et al. 1992: pl. 15, fig. 4), Clathrocorys (Nishimura 1990: figs 21.3, 22.1, 22.2, 23.5; Sugiyama 1994: pl. 2, figs 1, 2), Pteropilium (Nishimura & Yamauchi 1984: pl. 34, fig. 7), and Tripocyrtis (Nishimura 1990: figs 23.1, 23.2, 23.4). These genera have small size and they are frequently overlooked in many plankton studies. Nonetheless, some living images were illustrated for Callimitra (Anderson 1983: fig. 1.2.G; Matsuoka 1999: pl. 1, fig.1; 2017: fig.20; Zhang et al. 2018: 9, fig. 33; pl. 10, figs 31, 46, 47) and Clathrocanium (Suzuki et al. 2009b: figs 2O, 2P; Zhang et al. 2018: 10, fig. 4, p. 13, fig. 21).
VALIDITY OF GENERA
Callimitra
The precise anatomical description of Callimitra was written by Petrushevskaya (1981: 301) and revised by Goll (1979:
386) as follows: “[...] characterized by 3 large lattice panels extending laterally from the tip of the apical apophysis to the tips of each of the frontal and primary lateral apophyses.” Arachnothauma was described as follows: “ Shell cupola- or helm-shaped with three delicate convex appendages downwardly curved. From them originate pairs of divergent small lateral apophyses [...] From the top of the cephalis originates a similar appendage [...] with also lateral apophyses. Between them are distributed extremely thin threads that are linked again to other oblique threads. This structure gives the impression that a very small spider web has covered a very elegant beam structure ” (translation from Zacharias 1906: 566-567). This description of Arachnothauma and the type-illustration (Zacharias 1906: fig. 19) match those of Callimitra. Zacharias (1906) did not compare Arachnothauma to Callimitra. They are indeed clearly synonyms. The name Callimitra is older than Arachnothauma.
Clathrocanium
Clathrocanidium has the same type species as Clathrocanium. Clathrocanium, Clathrocorona, Arachnopilium, Clathrolychnus, Sethopera, and Tripocyrtis are defined in terms of their ontogenetic growth stages. Clathrocanium (Suzuki et al. 2009c: pl. 54, figs 5a-d), Sethopera (Haeckel 1887: pl. 97, fig. 11), and Tripocyrtis (Haeckel 1887: pl. 60, fig. 10) represent the youngest stage, without a perforated apical horn. Clathrocorona (Haeckel 1887: pl. 64, fig. 2), with perforated apical horn and three perforated basal feet, represents the next growth stage, and is illustrated in the Atlas as a supporting image for Clathrocanidium. The next growth stages are Clathrolychnus (Haeckel 1887: pl. 64, fig. 5), with a perforation connecting the apical horn and basal feet, followed by Arachnopilium (Haeckel 1887: pl. 64, fig. 7), with the development of a perforated thin cover around the three gates between the basal feet. Arachnopilium is illustrated as a supporting image for Clathrocorona and Clathrolychnus in the Atlas.
Superfamily LITHOCHYTRIDOIDEA Ehrenberg, 1846 n. stat.
Lithochytrina Ehrenberg, 1846: 385 [as a family]; 1847: 53 [as a family].
Lychnocanioidea – Petrushevskaya 1986: 132-132. — Afanasieva et al. 2005: S295-296. — Afanasieva & Amon 2006: 144.
DIAGNOSIS. — Lithochytridoidea consist of two- to three-segmented Nassellaria with a stout vertical apical horn, a spherical cephalis, a conical or globular thorax, as well as three feet or a relevant structure. The feet are principally connected to the D- and double L-rods of the cephalic initial spicular system. Expect for a few exceptions, an aperture is present.
REMARKS
The Lithochytridoidea consists of the Bekomidae and Lithochytrididae. Based on the results of the molecular phylogeny, Lamprotripus and Dictyopodium (= Pterocanium in original) form a tight, single group (Sandin et al. 2019).
Family BEKOMIDAE Dumitrica in De Wever, Dumitrica, Caulet, Nigrini & Caridroit, 2001
Bekomidae Dumitrica in De Wever, Dumitrica, Caulet, Nigrini & Caridroit, 2001: 284. — Matsuzaki et al. 2015: 63-64.
Bekominae – Afanasieva et al. 2005: S296. — Afanasieva & Amon 2006: 145.
TYPE GENUS. — Bekoma Riedel & Sanfilippo, 1971: 1592 [type species by monotypy: Bekoma bidarfensis Riedel & Sanfilippo, 1971: 1592].
INCLUDED GENERA. — Bekoma Riedel & Sanfilippo, 1971: 1592. — Bekomiforma Sanfilippo & Riedel, 1974: 1020. — Lamprotripus Haeckel, 1882: 431. — Orbula Foreman, 1973a: 437.
NOMINA DUBIA. — Stichocampe, Stichopterium.
DIAGNOSIS. — Bekomidae consist of two-segmented Lithochytridoidea (exclusive of Orbula) with six collar pores that form the basal ring of the cephalis, two free A- and V-rods in the cephalic cavity, and three feet. Except in the case of Lamprotripus, the cephalis is covered with a thick siliceous wall. The cephalic initial spicular system consists of A-, V-, D-, double l-, and double L-rods. A combination of A- and V-rods, or solely A-rod, forms one or more significant cylindrical apical horn(s). D- and double L-rods protrude from the cephalis and form three feet or rims on the thorax. The MB is located in the center of the basal aperture of the cephalis. The basal ring is directly connected to the D-, double l- and double L-rods. The basal ring tends to be located horizontally in the cephalic cavity. Although the basal ring is generally merged to the shell wall, it is well visible in older forms (Bekoma and Bekomiforma) but degraded in a younger form (Lamprotripus).
A protoplasm is observed in Lamprotripus. The endoplasm is opaque dark grey, filling the upper part of the shell at the level where three rod wings are separated from the shell. No algal symbionts are present.
STRATIGRAPHIC OCCURRENCE. — Middle Paleocene-Living.
REMARKS
The Bekomidae are distinguishable from the Lithochytrididae. The latter lack the double l-rod and have four collar pores instead of six and their MB is oblique to the collar stricture.The cephalic initial spicular system was illustrated for Bekoma (Nishimura 1992: pl. 5, figs 4, 5, 9, 11; pl. 8, fig. 5?), Bekomiforma (Sugiyama et al. 1992: pl. 20, fig. 1) and Lamprotripus (Nishimura & Yamauchi 1984: pl. 31, fig.1; Nishimura 1990: figs 26.6, 26.7, 29.6; Sugiyama et al. 1992: pl. 22, fig. 1). The diagnosis written above excludes the characteristics of “ Lamprotripus ” mawsoni (Riedel 1958). As this species lacks the double l- and V-rods (Sugiyama et al. 1992: pl. 16, figs 4, 5), it cannot be placed in Lamprotripus. This species is also grouped with Dictyopodium (= Pterocanium in original) but not Lamprotripus in the Clade I (Sandin et al. 2019). “ L.” mawsoni has three collar pores as opposed to four.Sugiyama et al. (1992: 18-19) conceptualized it as a new genus. The living appearance of Lamprotripus is documented (Suzuki & Not 2015: fig. 8.10.15).
Family LITHOCHYTRIDIDAE Ehrenberg, 1846
Lithochytrina Ehrenberg, 1846: 385 [as a family]; 1847: 53 [as a family]. — Schomburgk 1847: 124, 125 [as a family]. — Ehrenberg 1876: 156.
Lychnocanida Haeckel, 1882: 432 [below tribe].
Lithornithida Haeckel, 1882: 436 [nomen dubium, below tribe].
Lychnocaniinae – Petrushevskaya 1971a: 227-228; 1981: 239-240. — Afanasieva et al. 2005: S296. — Afanasieva & Amon 2006: 144.
Lychnocaniidae – Petrushevskaya & Kozlova 1972: 552. — Petrushevskaya 1975: 583; 1981: 229-230; 1986: 133. — Dumitrica 1979: 34. — Kozlova 1999: 127. — Afanasieva et al. 2005: S296. — Afanasieva & Amon 2006: 144. — Suzuki in Matsuzaki et al. 2015: 50.
Lithochytridinae – Petrushevskaya 1981: 244. — Afanasieva et al. 2005: 296. — Afanasieva & Amon 2006: 144.
TYPE GENUS. — Lithochytris Ehrenberg, 1846: 385 [type species by subsequent designation (Campbell 1954: D132): Lithochytris vespertilio Ehrenberg, 1874: 239].
INCLUDED GENERA. — Dictyopodium Ehrenberg, 1847: 54 (= Pterocanarium n. syn.; Pterocanidium and Pleuropodium synonymized by Riedel & Sanfilippo 1970: 529; Lychnodictyum synonymized by Lazarus et al. 1985: 196). — Inversumbella Nigrini & Caulet, 1992: 150. — Lithochytris Ehrenberg, 1846: 385 (= Lithochytridium with the same type species; Sethochytris synonymized by Petrushevskaya 1981: 247). — Lychnocanissa Haeckel, 1887: 1226 (= Acerahedrina, Acerocanium, Lychnocanoma synonymized by Riedel & Sanfilippo 1970: 529; Podocyrtecium n. syn.). — Lychnocanium Ehrenberg, 1846: 385 (= Dictyophimium with the same type species; Lithochytrodes synonymized byPetrushevskaya 1975: 583; Lychnocanella n. syn.). —? Verutotholus O’Connor, 1999: 13.
INVALID NAME. — Tetrahedrina.
NOMINA DUBIA. — Lithornithium, Tetraedrina.
NOMEN NUDUM. — Fenestracanthia.
DIAGNOSIS. — Lithochytrididae consist of two or three segmented Lithochytridoidea with four collar pores on the cephalic basal ring, a free A-rod in the cephalic cavity, and a very short to very long apical horn on the spherical cephalis. Three (rarely two) feet or wings are always present. The cephalic initial spicular system consists of MB, A-, D-, V- and double L-rods. No l-rods are observed. The basal ring is directly connected to the apical side end of MB, V-, and the double L-rods. Furthermore, the basal ring is sharply bended along the line, with the double L-rods. The apical side of the basal ring is merged with the shell wall but all four collar pores are easily recognizable. The V-rod occasionally extends outward from the cephalic wall. The MB is oriented slightly toward to the apical side. The double mp -arch (upper arch of the double AL-arch in the cephalis) is embedded in the cephalic wall and is occasionally visible, near the uppermost A-rod on the cephalis, under light microscopy. The D- and double L-rods merge with the shell wall, forming wall rims. These rods are also connected with each foot.
A protoplasm is observed in Dictyopodium. The endoplasm is transparent and appears as four lobes below the cephalis. The size of the lobe is variable, from very small near the cephalis to large close to the aperture. Many algal symbionts are distributed around the lobes. The endoplasm is observed inside or outside the shell. The pseudopodia are found radiating around the thorax. An axial projection is absent.
STRATIGRAPHIC OCCURRENCE. — Early Paleocene-Living.
REMARKS
The problem in defining Lithochytrididae originates from the poorly reported cephalic structure in the type genus Lithochytris and its closest genus Lychnocanium. The cephalic structure was only reported for Lithochytris (Nishimura 1990: figs 28.2, 28.3) and Lychnocanium (Nishimura 1990: fig.28.1). By contrast, the cephalic structure was repeatedly illustrated in Dictyopodium (Dumitrica 1973a: pl. 13, figs 3-6; Nishimura & Yamauchi 1984: pl. 30, figs 7, 9; Nishimura 1990: fig. 29.7; Sugiyama et al. 1992: pl. 24, figs 5-8, pl. 25, figs 1, 3, 4). To the best of our knowledge, the detailed structure of Dictyopodium is nearly the same as that of Lychnocanium but the former displays the most representative characters of Lithochytrididae. The cephalic structure of Lychnocanissa (originally Lychnocanium) was only observed in the late Eocene to early Miocene specimens (O’Connor 1997a: pl. 9, figs 9-12; 1999; pl. 4, figs 12-15, pl. 4, figs 22-27). However, their cephalic base is completely separate from the shell test while the basal ring is affixed to the shell test by numerous short radial beams. These characters are typical for the Theoperidae. High species diversity is documented in Lychnocanissa (originally Lychnocanoma) (Riedel & Sanfilippo 1970; Petrushevskaya 1981). Nonetheless, several species may not belong to this genus. Verutotholus is tentatively included in the Lithochytrididae though this genus has a double AL-arch, six collar pores and the presence of double l-rods (O’Connor 1999: pl. 2, figs 16, 20, 22b), more closely resembling the Bekomidae. An endemic Lychnocanissa with only two feet was originally described as Acerahedrina (Vinassa de Regny 1900). In regard to the cephalic structure of the Acerahedrina -form of Lychnocanissa (Nishimura 1990: figs 27.4-27.6; Sugiyama & Furutani 1992: pl. 17, fig. 2), the character of the cephalic base is similar to that of Dictyopodium and, thus, this form evidently belongs to the Lithochytrididae. The two feet of the Acerahedrina - form of Lychnocanissa are aligned parallel to the plane that includes MB-, D-, and V-rods. One of the feet appears to be connected with the D-rod while the other is disconnected from any initial rod.
The members of the Lithochytrididae and the valid genera names in the Lithochytrididae were historically misunderstood. As for the family, all Lithochytrididae genera except for “ Lychnocanoma ” and “ Pterocanium ” (the valid names are Lychnocanissa and Dictyopodium in this paper) were not treated in De Wever et al. (2001). De Wever et al. (2001) placed Dictyopodium in the Mesozoic family Ultranaporidae Pessagno 1977a. The current usage of the latter name has been already discussed and resolved by Matsuzaki et al. (2015: 49-50). The valid genus name and correct type species for Lychnocanium (Sanfilippo et al. 1973: 221; Petrushevskaya 1981: 242), “ Lychnocanoma ” (Riedel & Sanfilippo 1970: 529; Petrushevskaya & Kozlova 1972: 553; Petrushevskaya 1981: 241; Nishimura 1990: 132-133; O’Connor 1997a: 77-78; 1999: 24), and “ Pterocanium ” (the valid genus name is Dictyopodium in this paper) (Riedel & Sanfilippo 1970: 529; Petrushevskaya 1981: 237) were not fully agreed among previous researchers. The main argument concerned whether Lychnocanium lucerna Ehrenberg 1847 or Lychnocanium falciferum Ehrenberg, 1854 was the correct type species of Lychnocanium. A similar problem occurred between Pterocanium proserpinae Ehrenberg 1859 and Lithocampe aculeata Ehrenberg 1844b for the correct type species of Pterocanium.
The Lithochytrididae are commonly found from late Eocene sediments to the modern ocean, but the study of their evolution is limited. The evolutionary history of the genus Dictyopodium (= Pterocanium in original) was documented (Lazarus et al. 1985). One solution for the evolution of Lithochytris - Lychnocanium was proposed (Kling 1978: 234; Riedel & Sanfilippo 1981: fig. 12.11).
Knowledge of the living status of the Lithochytrididae is mainly based on Dictyopodium (Matsuoka 1993a: fig. 2.5; 1993b: pl. 5, figs 1, 2; 2017: fig. 23; Suzuki & Aita 2011: fig. 5N; Suzuki & Not 2015: fig. 8.11.17). Algal symbionts of Dictyopodium praetextum (Ehrenberg) were identified as Gymnoxanthella radiolariae but Brandtodinium nucleate remained absent. The identified symbiont is the same dinoflagellate species as those found in Acanthodesmia (Acanthodesmiidae) and Dictyocoryne (Euchitoniidae, Spumellaria) (Yuasa et al. 2016).
VALIDITY OF GENERA
Dictyopodium
The concept of the valid genus Dictyopodium is equivalent to the current usage of Pterocanium because Dictyopodium trilobum, the type species of Dictyopodium, has been classified under the current concept of Pterocanium for more than 130 years (Haeckel 1887). The type species of Pterocanarium is Pterocanium proserpinae, which has been classified in Pterocanium for over a century, but was synonymized with Podocyrtis charybdea by Petrushevskaya (1971a). Lazarus et al. (1985) reconstructed the phylogeny of late Neogene Pterocanium to include Pterocanium charybdeum and Pterocanium trilobum (originally P. charybdeum trilobum); subsequently, Pterocanarium was synonymized with Dictyopodium, and the genera Pterocanidium, Pleuropodium, and Lychnodictyum were synonymized with Dictyopodium. Among these, the oldest available name is Dictyopodium.
Lychnocanissa
In the Atlas, Lychnocanissa corresponds to Lychnocanoma sensu Foreman (1973b: 437), Sanfilippo et al. (1973: 221), Morley & Nigrini (1995: 80), and Suzuki in Matsuzaki et al. (2015: 50) and to Lychnocanium sensu Riedel & Sanfilippo (1970: 529), Petrushevskaya & Kozlova (1972: 553), Petrushevskaya (1981: 242), Nishimura (1990: 132-133), Kozlova (1999: 128), and O’Connor (1997a: 77-78; 1999: 24). Our concept is also equivalent to a combination of Lychnocanium and Lychnocanoma, sensu Tochilina & Vasilenko (2018a: 23). The type-illustration of Podocyrtecium shows three segmentations (Haeckel 1887: pl. 72, fig. 1), but this is likely incorrect because no three-segmented specimens similar to Lychnocanoma have been found. Lychnocanissa, Lychnocanoma, and Podocyrtecium were simultaneously published in Haeckel (1887: 1226 for Lychnocanissa, 1229 for Lychnocanoma and 1339 for Podocyrtecium). Selecting a valid genus is problematic. Campbell (1954: D124) considered Lychnocanissa the nominate subgenus of Lychnocanium. However, the type species of Lychnocanium, Lychnocanium lucerna, was not originally included in Lychnocanissa. Species included at that time included Lychnocanium falciferum, Lychnocanium fenestratum, Lychnocanium fortipes, Lychnocanium sigmopodium, Lychnocanium tetrapodium, Lychnocanium trichopus, and Lychnocanium tuberosum. Campbell (1954) did not designate a type species for Lychnocanissa. Therefore, we newly designated Lychnocanium falciferum as a type species in the Atlas. Lychnocanium falciferum was designated as the type species of Lychnocanium by Campbell (1954: D124), but many authors have commented that this designation is incorrect. One of the authors of the present study (NS) suggested that Lychnocanoma be validated several times over a period of 2 years; however, the final consensus is that Lychnocanissa is a valid genus. The validation of Lychnocanissa over Lychnocanoma obviously violates ICZN (1999) article 23.9, which states, “ 23.9.1. Prevailing usage must be maintained when the following conditions are both met: 23.9.1. The senior synonym [...] has not been used as a valid name after 1899, and 23.9.1.2. The junior synonym [...] has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years and encompassing a span of not less than 10 years.”
Lychnocanium
There are two concepts of Lychnocanium, one based on the designation of Lychnocanium falciferum as the type species by Campbell (1954: D124), and the other based on the designation of Lychnocanium lucerna, the first species assigned to Lychnocanium, as the type species by Ehrenberg (1847). This confusion has continued since the early 1970s (Riedel & Sanfilippo 1970; Sanfilippo et al. 1973; Petrushevskaya 1981; O’Connor 1997a; Tochilina & Vasilenko 2018a). The only correct solution is for Lychnocanium lucerna to be designated as the type species, according to ICZN (1999) article 69.3, which states, “ Type species by subsequent monotypy. If only one nominal species was first subsequently included in a nominal genus or subgenus without included species, that nominal species is automatically fixed as the type species, by subsequent monotypy. ” Under this monotypy, the concept of Lychnocanium sensu Riedel & Sanfilippo (1970: 529), Petrushevskaya & Kozlova (1972: 553), Petrushevskaya (1981: 241), Nishimura (1990: 132-133), Kozlova (1999: 128) and O’Connor (1997a: 77-78; 1999: 24), and Tochilina & Vasilenko (2018a: 23) is incorrect.
Under the correct type species, Lychnocanium is synonymized with Lithochytrodes and Lychnocanella. Dictyophimium has the same type species as Lychnocanium. Lychnocanella was defined by Kozlova (1999: 127) and is translated as follows: “ Threesegmented shell with three well-developed feet, protruding from the base of the thorax. This genus differs from Lychnocanium Ehrenberg [note: type species L. lucerna in this case] only by a pear-shaped thorax with an elongated proximal part. ” This difference is a major distinguishing feature at the species level but not at the genus level. Petrushevskaya (1981: 241) strongly disagreed with the relationship between Lychnocanium and Lychnocanella, but this opinion was based on the incorrect type species, L. falciferum, not L. lucerna. Lithochytrodes was synonymized with Lychnocanella by Petrushevskaya (1975: 583). Later comments by Petrushevskaya (1981: 256) are translated as follows: “ Characteristics similar to those of Lychnocanella. Differences include a more precise distinction between the second and third segments [...] about 10-20 longitudinal rows of pores [...] Lithochytrodes is proposed as a subjective synonym of Lychnocanella.” Among these groups, Lychnocanium is the oldest available name.
Superfamily PTEROCORYTHOIDEA Haeckel, 1882
Pterocorida Haeckel, 1882: 435 [below a tribe].
Pterocoryacea – Kozur & Mostler 1984: 122.
Pterocorythoidea – Suzuki in Matsuzaki et al. 2015: 49-50.
DIAGNOSIS. — Pterocorythoidea consist of three segmented Nassellaria with a stout, vertical apical horn, a spherical or elongated cephalis, a truncated conical thorax, and a very variable size last segment. Generally, no feet extend from the abdomen. If feet are present and extend from the abdomen, they remain disconnected from any rods of the cephalis spicular system. An aperture is observable except in the case of a few exceptions. The A-rod side of the MB is positioned very close to the shell wall or may be merged, becoming a part of the shell wall. The V-rod side of the MB is generally located at the center of the cephalic basal aperture. The V-rod is oriented upward at an angle of 30-45 degrees from the horizontal plane. The stability of the cephalis spicular system varies throughout families.
REMARKS
The Pterocorythoidea include the Lophocyrtiidae, Pterocorythidae, Theocotylidae and Theoperidae.As the Pterocorythidae is the only family with living genera (Anthocyrtidium, Pterocorys, and Theocorythium), the taxonomic position of the remaining three families is only based on morphological data. Matsuzaki et al. (2015) also included the Lithochytrididae (originally Lychnocaniidae) but did not conclude Lophocyrtiidae, Theocotylidae and Theoperidae as these families were not encountered in their study. Herein, the diagnosis is altered in order to align with these Cenozoic families. As three families of the Pterocorythoidea are extinct, the evolution between them can only be reconstructed by examining the fossil evidence. From an anatomical perspective, the Spongiopodium -form of Paralampterium has characters that resemble a combination of those found in Lophocyrtiidae and Theoperidae. Calocyclas has a mix of characters found in the Pterocorythidae and the Theocotylidae.
Superfamily LITHOCHYTRIDOIDEA Ehrenberg, 1846 n. stat.
Lithochytrina Ehrenberg, 1846: 385 [as a family]; 1847: 53 [as a family].
Lychnocanioidea – Petrushevskaya 1986: 132-132. — Afanasieva et al. 2005: S295-296. — Afanasieva & Amon 2006: 144.
DIAGNOSIS. — Lithochytridoidea consist of two- to three-segmented Nassellaria with a stout vertical apical horn, a spherical cephalis, a conical or globular thorax, as well as three feet or a relevant structure. The feet are principally connected to the D- and double L-rods of the cephalic initial spicular system. Expect for a few exceptions, an aperture is present.
REMARKS
The Lithochytridoidea consists of the Bekomidae and Lithochytrididae. Based on the results of the molecular phylogeny, Lamprotripus and Dictyopodium (= Pterocanium in original) form a tight, single group (Sandin et al. 2019).
Family BEKOMIDAE Dumitrica in De Wever, Dumitrica, Caulet, Nigrini & Caridroit, 2001
Bekomidae Dumitrica in De Wever, Dumitrica, Caulet, Nigrini & Caridroit, 2001: 284. — Matsuzaki et al. 2015: 63-64.
Bekominae – Afanasieva et al. 2005: S296. — Afanasieva & Amon 2006: 145.
TYPE GENUS. — Bekoma Riedel & Sanfilippo, 1971: 1592 [type species by monotypy: Bekoma bidarfensis Riedel & Sanfilippo, 1971: 1592].
INCLUDED GENERA. — Bekoma Riedel & Sanfilippo, 1971: 1592. — Bekomiforma Sanfilippo & Riedel, 1974: 1020. — Lamprotripus Haeckel, 1882: 431. — Orbula Foreman, 1973a: 437.
NOMINA DUBIA. — Stichocampe, Stichopterium.
DIAGNOSIS. — Bekomidae consist of two-segmented Lithochytridoidea (exclusive of Orbula) with six collar pores that form the basal ring of the cephalis, two free A- and V-rods in the cephalic cavity, and three feet. Except in the case of Lamprotripus, the cephalis is covered with a thick siliceous wall. The cephalic initial spicular system consists of A-, V-, D-, double l-, and double L-rods. A combination of A- and V-rods, or solely A-rod, forms one or more significant cylindrical apical horn(s). D- and double L-rods protrude from the cephalis and form three feet or rims on the thorax. The MB is located in the center of the basal aperture of the cephalis. The basal ring is directly connected to the D-, double l- and double L-rods. The basal ring tends to be located horizontally in the cephalic cavity. Although the basal ring is generally merged to the shell wall, it is well visible in older forms (Bekoma and Bekomiforma) but degraded in a younger form (Lamprotripus).
A protoplasm is observed in Lamprotripus. The endoplasm is opaque dark grey, filling the upper part of the shell at the level where three rod wings are separated from the shell. No algal symbionts are present.
STRATIGRAPHIC OCCURRENCE. — Middle Paleocene-Living.
REMARKS
The Bekomidae are distinguishable from the Lithochytrididae. The latter lack the double l-rod and have four collar pores instead of six and their MB is oblique to the collar stricture.The cephalic initial spicular system was illustrated for Bekoma (Nishimura 1992: pl. 5, figs 4, 5, 9, 11; pl. 8, fig. 5?), Bekomiforma (Sugiyama et al. 1992: pl. 20, fig. 1) and Lamprotripus (Nishimura & Yamauchi 1984: pl. 31, fig.1; Nishimura 1990: figs 26.6, 26.7, 29.6; Sugiyama et al. 1992: pl. 22, fig. 1). The diagnosis written above excludes the characteristics of “ Lamprotripus ” mawsoni (Riedel 1958). As this species lacks the double l- and V-rods (Sugiyama et al. 1992: pl. 16, figs 4, 5), it cannot be placed in Lamprotripus. This species is also grouped with Dictyopodium (= Pterocanium in original) but not Lamprotripus in the Clade I (Sandin et al. 2019). “ L.” mawsoni has three collar pores as opposed to four.Sugiyama et al. (1992: 18-19) conceptualized it as a new genus. The living appearance of Lamprotripus is documented (Suzuki & Not 2015: fig. 8.10.15).
Family LITHOCHYTRIDIDAE Ehrenberg, 1846
Lithochytrina Ehrenberg, 1846: 385 [as a family]; 1847: 53 [as a family]. — Schomburgk 1847: 124, 125 [as a family]. — Ehrenberg 1876: 156.
Lychnocanida Haeckel, 1882: 432 [below tribe].
Lithornithida Haeckel, 1882: 436 [nomen dubium, below tribe].
Lychnocaniinae – Petrushevskaya 1971a: 227-228; 1981: 239-240. — Afanasieva et al. 2005: S296. — Afanasieva & Amon 2006: 144.
Lychnocaniidae – Petrushevskaya & Kozlova 1972: 552. — Petrushevskaya 1975: 583; 1981: 229-230; 1986: 133. — Dumitrica 1979: 34. — Kozlova 1999: 127. — Afanasieva et al. 2005: S296. — Afanasieva & Amon 2006: 144. — Suzuki in Matsuzaki et al. 2015: 50.
Lithochytridinae – Petrushevskaya 1981: 244. — Afanasieva et al. 2005: 296. — Afanasieva & Amon 2006: 144.
TYPE GENUS. — Lithochytris Ehrenberg, 1846: 385 [type species by subsequent designation (Campbell 1954: D132): Lithochytris vespertilio Ehrenberg, 1874: 239].
INCLUDED GENERA. — Dictyopodium Ehrenberg, 1847: 54 (= Pterocanarium n. syn.; Pterocanidium and Pleuropodium synonymized by Riedel & Sanfilippo 1970: 529; Lychnodictyum synonymized by Lazarus et al. 1985: 196). — Inversumbella Nigrini & Caulet, 1992: 150. — Lithochytris Ehrenberg, 1846: 385 (= Lithochytridium with the same type species; Sethochytris synonymized by Petrushevskaya 1981: 247). — Lychnocanissa Haeckel, 1887: 1226 (= Acerahedrina, Acerocanium, Lychnocanoma synonymized by Riedel & Sanfilippo 1970: 529; Podocyrtecium n. syn.). — Lychnocanium Ehrenberg, 1846: 385 (= Dictyophimium with the same type species; Lithochytrodes synonymized byPetrushevskaya 1975: 583; Lychnocanella n. syn.). —? Verutotholus O’Connor, 1999: 13.
INVALID NAME. — Tetrahedrina.
NOMINA DUBIA. — Lithornithium, Tetraedrina.
NOMEN NUDUM. — Fenestracanthia.
DIAGNOSIS. — Lithochytrididae consist of two or three segmented Lithochytridoidea with four collar pores on the cephalic basal ring, a free A-rod in the cephalic cavity, and a very short to very long apical horn on the spherical cephalis. Three (rarely two) feet or wings are always present. The cephalic initial spicular system consists of MB, A-, D-, V- and double L-rods. No l-rods are observed. The basal ring is directly connected to the apical side end of MB, V-, and the double L-rods. Furthermore, the basal ring is sharply bended along the line, with the double L-rods. The apical side of the basal ring is merged with the shell wall but all four collar pores are easily recognizable. The V-rod occasionally extends outward from the cephalic wall. The MB is oriented slightly toward to the apical side. The double mp -arch (upper arch of the double AL-arch in the cephalis) is embedded in the cephalic wall and is occasionally visible, near the uppermost A-rod on the cephalis, under light microscopy. The D- and double L-rods merge with the shell wall, forming wall rims. These rods are also connected with each foot.
A protoplasm is observed in Dictyopodium. The endoplasm is transparent and appears as four lobes below the cephalis. The size of the lobe is variable, from very small near the cephalis to large close to the aperture. Many algal symbionts are distributed around the lobes. The endoplasm is observed inside or outside the shell. The pseudopodia are found radiating around the thorax. An axial projection is absent.
STRATIGRAPHIC OCCURRENCE. — Early Paleocene-Living.
REMARKS
The problem in defining Lithochytrididae originates from the poorly reported cephalic structure in the type genus Lithochytris and its closest genus Lychnocanium. The cephalic structure was only reported for Lithochytris (Nishimura 1990: figs 28.2, 28.3) and Lychnocanium (Nishimura 1990: fig.28.1). By contrast, the cephalic structure was repeatedly illustrated in Dictyopodium (Dumitrica 1973a: pl. 13, figs 3-6; Nishimura & Yamauchi 1984: pl. 30, figs 7, 9; Nishimura 1990: fig. 29.7; Sugiyama et al. 1992: pl. 24, figs 5-8, pl. 25, figs 1, 3, 4). To the best of our knowledge, the detailed structure of Dictyopodium is nearly the same as that of Lychnocanium but the former displays the most representative characters of Lithochytrididae. The cephalic structure of Lychnocanissa (originally Lychnocanium) was only observed in the late Eocene to early Miocene specimens (O’Connor 1997a: pl. 9, figs 9-12; 1999; pl. 4, figs 12-15, pl. 4, figs 22-27). However, their cephalic base is completely separate from the shell test while the basal ring is affixed to the shell test by numerous short radial beams. These characters are typical for the Theoperidae. High species diversity is documented in Lychnocanissa (originally Lychnocanoma) (Riedel & Sanfilippo 1970; Petrushevskaya 1981). Nonetheless, several species may not belong to this genus. Verutotholus is tentatively included in the Lithochytrididae though this genus has a double AL-arch, six collar pores and the presence of double l-rods (O’Connor 1999: pl. 2, figs 16, 20, 22b), more closely resembling the Bekomidae. An endemic Lychnocanissa with only two feet was originally described as Acerahedrina (Vinassa de Regny 1900). In regard to the cephalic structure of the Acerahedrina -form of Lychnocanissa (Nishimura 1990: figs 27.4-27.6; Sugiyama & Furutani 1992: pl. 17, fig. 2), the character of the cephalic base is similar to that of Dictyopodium and, thus, this form evidently belongs to the Lithochytrididae. The two feet of the Acerahedrina - form of Lychnocanissa are aligned parallel to the plane that includes MB-, D-, and V-rods. One of the feet appears to be connected with the D-rod while the other is disconnected from any initial rod.
The members of the Lithochytrididae and the valid genera names in the Lithochytrididae were historically misunderstood. As for the family, all Lithochytrididae genera except for “ Lychnocanoma ” and “ Pterocanium ” (the valid names are Lychnocanissa and Dictyopodium in this paper) were not treated in De Wever et al. (2001). De Wever et al. (2001) placed Dictyopodium in the Mesozoic family Ultranaporidae Pessagno 1977a. The current usage of the latter name has been already discussed and resolved by Matsuzaki et al. (2015: 49-50). The valid genus name and correct type species for Lychnocanium (Sanfilippo et al. 1973: 221; Petrushevskaya 1981: 242), “ Lychnocanoma ” (Riedel & Sanfilippo 1970: 529; Petrushevskaya & Kozlova 1972: 553; Petrushevskaya 1981: 241; Nishimura 1990: 132-133; O’Connor 1997a: 77-78; 1999: 24), and “ Pterocanium ” (the valid genus name is Dictyopodium in this paper) (Riedel & Sanfilippo 1970: 529; Petrushevskaya 1981: 237) were not fully agreed among previous researchers. The main argument concerned whether Lychnocanium lucerna Ehrenberg 1847 or Lychnocanium falciferum Ehrenberg, 1854 was the correct type species of Lychnocanium. A similar problem occurred between Pterocanium proserpinae Ehrenberg 1859 and Lithocampe aculeata Ehrenberg 1844b for the correct type species of Pterocanium.
The Lithochytrididae are commonly found from late Eocene sediments to the modern ocean, but the study of their evolution is limited. The evolutionary history of the genus Dictyopodium (= Pterocanium in original) was documented (Lazarus et al. 1985). One solution for the evolution of Lithochytris - Lychnocanium was proposed (Kling 1978: 234; Riedel & Sanfilippo 1981: fig. 12.11).
Knowledge of the living status of the Lithochytrididae is mainly based on Dictyopodium (Matsuoka 1993a: fig. 2.5; 1993b: pl. 5, figs 1, 2; 2017: fig. 23; Suzuki & Aita 2011: fig. 5N; Suzuki & Not 2015: fig. 8.11.17). Algal symbionts of Dictyopodium praetextum (Ehrenberg) were identified as Gymnoxanthella radiolariae but Brandtodinium nucleate remained absent. The identified symbiont is the same dinoflagellate species as those found in Acanthodesmia (Acanthodesmiidae) and Dictyocoryne (Euchitoniidae, Spumellaria) (Yuasa et al. 2016).
VALIDITY OF GENERA
Dictyopodium
The concept of the valid genus Dictyopodium is equivalent to the current usage of Pterocanium because Dictyopodium trilobum, the type species of Dictyopodium, has been classified under the current concept of Pterocanium for more than 130 years (Haeckel 1887). The type species of Pterocanarium is Pterocanium proserpinae, which has been classified in Pterocanium for over a century, but was synonymized with Podocyrtis charybdea by Petrushevskaya (1971a). Lazarus et al. (1985) reconstructed the phylogeny of late Neogene Pterocanium to include Pterocanium charybdeum and Pterocanium trilobum (originally P. charybdeum trilobum); subsequently, Pterocanarium was synonymized with Dictyopodium, and the genera Pterocanidium, Pleuropodium, and Lychnodictyum were synonymized with Dictyopodium. Among these, the oldest available name is Dictyopodium.
Lychnocanissa
In the Atlas, Lychnocanissa corresponds to Lychnocanoma sensu Foreman (1973b: 437), Sanfilippo et al. (1973: 221), Morley & Nigrini (1995: 80), and Suzuki in Matsuzaki et al. (2015: 50) and to Lychnocanium sensu Riedel & Sanfilippo (1970: 529), Petrushevskaya & Kozlova (1972: 553), Petrushevskaya (1981: 242), Nishimura (1990: 132-133), Kozlova (1999: 128), and O’Connor (1997a: 77-78; 1999: 24). Our concept is also equivalent to a combination of Lychnocanium and Lychnocanoma, sensu Tochilina & Vasilenko (2018a: 23). The type-illustration of Podocyrtecium shows three segmentations (Haeckel 1887: pl. 72, fig. 1), but this is likely incorrect because no three-segmented specimens similar to Lychnocanoma have been found. Lychnocanissa, Lychnocanoma, and Podocyrtecium were simultaneously published in Haeckel (1887: 1226 for Lychnocanissa, 1229 for Lychnocanoma and 1339 for Podocyrtecium). Selecting a valid genus is problematic. Campbell (1954: D124) considered Lychnocanissa the nominate subgenus of Lychnocanium. However, the type species of Lychnocanium, Lychnocanium lucerna, was not originally included in Lychnocanissa. Species included at that time included Lychnocanium falciferum, Lychnocanium fenestratum, Lychnocanium fortipes, Lychnocanium sigmopodium, Lychnocanium tetrapodium, Lychnocanium trichopus, and Lychnocanium tuberosum. Campbell (1954) did not designate a type species for Lychnocanissa. Therefore, we newly designated Lychnocanium falciferum as a type species in the Atlas. Lychnocanium falciferum was designated as the type species of Lychnocanium by Campbell (1954: D124), but many authors have commented that this designation is incorrect. One of the authors of the present study (NS) suggested that Lychnocanoma be validated several times over a period of 2 years; however, the final consensus is that Lychnocanissa is a valid genus. The validation of Lychnocanissa over Lychnocanoma obviously violates ICZN (1999) article 23.9, which states, “ 23.9.1. Prevailing usage must be maintained when the following conditions are both met: 23.9.1. The senior synonym [...] has not been used as a valid name after 1899, and 23.9.1.2. The junior synonym [...] has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years and encompassing a span of not less than 10 years.”
Lychnocanium
There are two concepts of Lychnocanium, one based on the designation of Lychnocanium falciferum as the type species by Campbell (1954: D124), and the other based on the designation of Lychnocanium lucerna, the first species assigned to Lychnocanium, as the type species by Ehrenberg (1847). This confusion has continued since the early 1970s (Riedel & Sanfilippo 1970; Sanfilippo et al. 1973; Petrushevskaya 1981; O’Connor 1997a; Tochilina & Vasilenko 2018a). The only correct solution is for Lychnocanium lucerna to be designated as the type species, according to ICZN (1999) article 69.3, which states, “ Type species by subsequent monotypy. If only one nominal species was first subsequently included in a nominal genus or subgenus without included species, that nominal species is automatically fixed as the type species, by subsequent monotypy. ” Under this monotypy, the concept of Lychnocanium sensu Riedel & Sanfilippo (1970: 529), Petrushevskaya & Kozlova (1972: 553), Petrushevskaya (1981: 241), Nishimura (1990: 132-133), Kozlova (1999: 128) and O’Connor (1997a: 77-78; 1999: 24), and Tochilina & Vasilenko (2018a: 23) is incorrect.
Under the correct type species, Lychnocanium is synonymized with Lithochytrodes and Lychnocanella. Dictyophimium has the same type species as Lychnocanium. Lychnocanella was defined by Kozlova (1999: 127) and is translated as follows: “ Threesegmented shell with three well-developed feet, protruding from the base of the thorax. This genus differs from Lychnocanium Ehrenberg [note: type species L. lucerna in this case] only by a pear-shaped thorax with an elongated proximal part. ” This difference is a major distinguishing feature at the species level but not at the genus level. Petrushevskaya (1981: 241) strongly disagreed with the relationship between Lychnocanium and Lychnocanella, but this opinion was based on the incorrect type species, L. falciferum, not L. lucerna. Lithochytrodes was synonymized with Lychnocanella by Petrushevskaya (1975: 583). Later comments by Petrushevskaya (1981: 256) are translated as follows: “ Characteristics similar to those of Lychnocanella. Differences include a more precise distinction between the second and third segments [...] about 10-20 longitudinal rows of pores [...] Lithochytrodes is proposed as a subjective synonym of Lychnocanella.” Among these groups, Lychnocanium is the oldest available name.
Superfamily PTEROCORYTHOIDEA Haeckel, 1882
Pterocorida Haeckel, 1882: 435 [below a tribe].
Pterocoryacea – Kozur & Mostler 1984: 122.
Pterocorythoidea – Suzuki in Matsuzaki et al. 2015: 49-50.
DIAGNOSIS. — Pterocorythoidea consist of three segmented Nassellaria with a stout, vertical apical horn, a spherical or elongated cephalis, a truncated conical thorax, and a very variable size last segment. Generally, no feet extend from the abdomen. If feet are present and extend from the abdomen, they remain disconnected from any rods of the cephalis spicular system. An aperture is observable except in the case of a few exceptions. The A-rod side of the MB is positioned very close to the shell wall or may be merged, becoming a part of the shell wall. The V-rod side of the MB is generally located at the center of the cephalic basal aperture. The V-rod is oriented upward at an angle of 30-45 degrees from the horizontal plane. The stability of the cephalis spicular system varies throughout families.
REMARKS
The Pterocorythoidea include the Lophocyrtiidae, Pterocorythidae, Theocotylidae and Theoperidae.As the Pterocorythidae is the only family with living genera (Anthocyrtidium, Pterocorys, and Theocorythium), the taxonomic position of the remaining three families is only based on morphological data. Matsuzaki et al. (2015) also included the Lithochytrididae (originally Lychnocaniidae) but did not conclude Lophocyrtiidae, Theocotylidae and Theoperidae as these families were not encountered in their study. Herein, the diagnosis is altered in order to align with these Cenozoic families. As three families of the Pterocorythoidea are extinct, the evolution between them can only be reconstructed by examining the fossil evidence. From an anatomical perspective, the Spongiopodium -form of Paralampterium has characters that resemble a combination of those found in Lophocyrtiidae and Theoperidae. Calocyclas has a mix of characters found in the Pterocorythidae and the Theocotylidae.
Superfamily PTEROCORYTHOIDEA Haeckel, 1882
Pterocorida Haeckel, 1882: 435 [below a tribe].
Pterocoryacea – Kozur & Mostler 1984: 122.
Pterocorythoidea – Suzuki in Matsuzaki et al. 2015: 49-50.
DIAGNOSIS. — Pterocorythoidea consist of three segmented Nassellaria with a stout, vertical apical horn, a spherical or elongated cephalis, a truncated conical thorax, and a very variable size last segment. Generally, no feet extend from the abdomen. If feet are present and extend from the abdomen, they remain disconnected from any rods of the cephalis spicular system. An aperture is observable except in the case of a few exceptions. The A-rod side of the MB is positioned very close to the shell wall or may be merged, becoming a part of the shell wall. The V-rod side of the MB is generally located at the center of the cephalic basal aperture. The V-rod is oriented upward at an angle of 30-45 degrees from the horizontal plane. The stability of the cephalis spicular system varies throughout families.
REMARKS
The Pterocorythoidea include the Lophocyrtiidae, Pterocorythidae, Theocotylidae and Theoperidae.As the Pterocorythidae is the only family with living genera (Anthocyrtidium, Pterocorys, and Theocorythium), the taxonomic position of the remaining three families is only based on morphological data. Matsuzaki et al. (2015) also included the Lithochytrididae (originally Lychnocaniidae) but did not conclude Lophocyrtiidae, Theocotylidae and Theoperidae as these families were not encountered in their study. Herein, the diagnosis is altered in order to align with these Cenozoic families. As three families of the Pterocorythoidea are extinct, the evolution between them can only be reconstructed by examining the fossil evidence. From an anatomical perspective, the Spongiopodium -form of Paralampterium has characters that resemble a combination of those found in Lophocyrtiidae and Theoperidae. Calocyclas has a mix of characters found in the Pterocorythidae and the Theocotylidae.