RHOPALOSYRINGIIDAE Empson-Morin, 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 : 482

Family RHOPALOSYRINGIIDAE Empson-Morin, 1981

Rhopalosyringiidae Empson-Morin, 1981 : 264. — O’Dogherty 1994: 158. — Bak 1999: 156.

Lithocampaninae Petrushevskaya, 1981: 115-116 [nomen dubium]. — Afanasieva et al. 2005: S295. — Afanasieva & Amon 2006: 143.

TYPE GENUS. — Rhopalosyringium Campbell & Clark, 1944b: 30 [type species by monotypy: Rhopalosyringium magnificum Campbell & Clark, 1944b: 30 ].

INCLUDED GENERA (CENOZOIC ONLY). — Artostrobus Haeckel, 1887: 1481 (= Artostrobulus with the same type species). — Botryometra Petrushevskaya, 1975: 590 . — Ectonocorys Foreman, 1968: 40 . — Pterocyrtidium Bütschli, 1882: 531 . — Rhopalosyringium Campbell & Clark, 1944b: 30 (= Calompterium n. syn.).

NOMEN DUBIUM. — Lithocampana .

DIAGNOSIS. — The overall size of the Cenozoic representatives of the genus is small. Two (rarely three) segments are observed with or without a collar constriction. The cephalis is poreless or contains small relict pores. A single vertical apical horn emerges from a free A-rod in the cephalic cavity, an MB is obliquely oriented toward the A-rod side, and a V-rod is found oriented upward relative to the shell wall or ventral tube. The above-mentioned features are well visible under a light microscope. Double ap -arches (type of AL-arches) are also visible on the cephalic wall. The cephalic initial spicular system is composed of MB, A-, V-, D-, double L- and double l-rods. The Ax-rod is present or absent. In Pterocorythium , at least, the basal ring is separated from the shell wall and directly connected to the V-, double L- and double l-rods to form four collar pores. The basal ring bends along the line with the double L-rod. The orientation of the MB upwards to the A-rod side implies that the double pore of the VL-arch rises up to the V-rod side and the double pore of the Ll-arch also rises up to the D-rod side. The A-, D-, V- and double L-rods are directly connected to the shell wall. Several rods are laterally distributed around the basal ring and connected with the shell wall. Excepting A- and V-rods, no vertical rods are present. Lateral rods include the D-rods, the double L-rod and several sets of double supplement rods that emerge from the Ll-arch. These rods that are connected to the basal ring are not recognizable under a light microscope. A relatively robust double arch between the l-rod and the A-rod lateral end of MB (named MA-arch) is also present in some specimens. D- and double L-rods extend outwards from the thorax near the cephalis and become external spines in Cenozoic members.

STRATIGRAPHIC OCCURRENCE. — Early Bajocian-Living.

REMARKS

The representatives of the genus Artostrobus in the Cenozoic have as common character the small size of their test. No molecular support data have been obtained for this family, but the presence of a ventral tube or a ventral tube-like structure is similar to both Carpocaniidae and Artostrobiidae . This family have a basal ring isolated from the shell wall, indicating some similarity with the Carpocaniidae . However, the overall appearance and the presence of apical horns suggest a larger similarity to the Artostrobiidae . As commented in the remarks for Lineage II, these three families may potentially be grouped into a single superfamily. Artostrobus was once placed in the Plectopyramididae (originally Acropyramididae in De Wever et al. 2001: 246 ); meanwhile Botryometra and Rhopalosyringium were both placed in the Cannobotrydidae (originally Cannobotryidae in De Wever et al. 2001: 244 ). Ectonocorys and Pterocyrtidium were not treated in De Wever et al. (2001). Originally, they were grouped by the latter on the basis of a common cephalic structure; however, the initial spicular system have not been examined in SEM analyses except for Pterocyrtidium ( O’Connor 1999: pl. 4, figs 21a, 21b). Therefore, the details of the cephalic structure largely relied on the SEM photos of Pterocyrtidium ( O’Connor 1999: pl. 4, figs 21a, 21b) with references to a drawing of Artostrobus ( Petrushevskaya 1967: figs 56, 57; 1968: fig. 4; 1971a: figs 82.IX, 82.X, 82.XII) and Botryometra ( Petrushevskaya 1971a: figs 79.I, 79.II).

VALIDITY OF GENERA

Rhopalosyringium

The synonymy between Rhopalosyringium and Calompterium is in debate among the authors of this paper. The cephalic structure of the Cenozoic Rhopalosyringium and the topotypic Calompterium specimens are quite similar externally. However, the potential topotype “ Calocyclas rachiphora Clark & Campbell, 1945 ” from Laguna Seca Creek section of the Kreyenhagen Formation, south of Los Banos ( Blueford & White 1984:67-68; pl. 2, fig. 4), lacks a rhopalosyringiid initial spicular system. The older synonym is Rhopalosyringium .