THEOPILIIDAE Haeckel, 1882

Family THEOPILIIDAE Haeckel, 1882 sensu Caulet emend. herein

Theopilida Haeckel, 1882: 435 [as a tribe]; 1887: 1313, 1315 [as a subfamily].

Theopilinae [sic] – Clark & Campbell 1942: 80 (= Theopiliinae). — Campbell & Clark 1944a: 46; 1944b: 29. — Chediya 1959: 213.

Theopiliidae – Campbell 1954: D130. — De Wever et al. 2001: 238, 239. — Matsuzaki et al. 2015: 60.

Theopiliinae – Campbell 1954: D130. — Petrushevskaya 1981: 134- 137; 1986: 134. — Afanasieva et al. 2005: S294. — Afanasieva & Amon 2006: 141.

TYPE GENUS. — Theopilium Haeckel, 1882: 435 [type species by subsequent designation (Campbell 1954: D130): Theopilium tricostatum Haeckel, 1887: 1322] = junior subjective synonym of Eucecryphalus Haeckel, 1861b: 836 [type species by subsequent designation (Haeckel 1887: 1221): Eucecryphalus gegenbauri Haeckel, 1861b: 836].

INCLUDED GENERA. — Clathrocycloma Haeckel, 1887: 1388. — Eucecryphalus Haeckel, 1861b: 836 (= Eucecryphalium with the same type species; Cecryphalium, Corocalyptra synonymized by Petrushevskaya 1971a; 146; Theopilium synonymized by Sanfilippo & Riedel 1992: 31).

NOMINA DUBIA. — Eucyrtomphalus, Theocalyptra.

DIAGNOSIS. — Theopilioidea with two cephalic spines (rod-like apical and ventral horns). No feet are observed. The cephalis has pores. The thorax is constructed by a fragile, polygonal pore frame and it is generally conical with a straight outline. The thorax may or may not have a weak neck on its upper part. The width of the pore frames is equivalent to the bars between the adjacent pores as well as to the junction points among the pores. In some members, a velum or velum-like periphery develops around the thorax aperture. The

cephalic initial spicular system consists of MB, A-, V-, D-, double L-rods. The double l-rod merges into the shell wall. The basal ring is absent. The MB is generally located at a similar height to the cephalic constriction and is horizontally or obliquely oriented. The length of the MB is one-third to one-half of the cephalis diameter. The A-rod is long, and rises almost vertically to penetrate the cephalic wall forming a rod-like apical horn. The V-rod is relatively long and forms a ventral horn. No ventral tube is observed. In some members, the D-rod extends almost horizontally to become a spine, outside the shell. The double L-rod extends relatively downward and protrudes as spine from the shell wall. In other cases, the distal part of the double L-rod has three branches on the cephalic wall, forming a part of the pore frame.

The endoplasm is transparent to light amber in color. Its size is too small and it is located above the neckline on the upper part of the thorax. The terminal projection is visible but the axial projection is absent.

STRATIGRAPHIC OCCURRENCE. — early Early Miocene-Living.

REMARKS

The cephalic initial spicular system was illustrated for both Clathrocycloma (Sugiyama & Furutani 1992: pl. 18, fig. 4) and Eucecryphalus (Nishimura 1990: figs 20.1, 26.4, 26.5; Sugiyama et al. 1992: pl. 21, fig. 7). Matsuzaki et al. (2015: 60) documented the cephalic initial spicular system of the Eucecryphalus in detail. Sandin et al. (2019: supplement 1) drew a schematic image of this genus, although this schematic drawing omits the double l-rod. The presence of two apical spines and the absence of a ventral tube in Theopiliidae easily distinguish them from the Anthocyrtididae. Eucecryphalus was once grouped with Cycladophora (Cycladophoridae) due to similarity in their cephalic initial spicular system (Matsuzaki et al. 2015: 60), but this grouping was discarded by a distinctive separation in molecular phylogeny at the lineage level (Sandin et al. 2019). As highlighted in the remarks for the Cycladophoridae in this paper, significant differences between the Theopiliidae and Cycladophoridae have not yet been confirmed. Typical Theopiliidae are characterized by a fragile thorax with a conical straight outline and many polygonal pores with same width frames. On the other hand, the Cycladophoridae likely have a robust thorax with a smaller number of rounded pores whose frames tend to widen around the junction of three of more pores. Cycladophoridae also tend to have a well-necked upper thorax (“pedestal” by Popova 1989). This tendency, however, is not so clear and some of these features may simply be lacking at species level. Most species introduced by Lombari & Lazarus (1988) seem to belong to Clathrocycloma. “Living” and protoplasm images were published for Eucecryphalus (Sashida & Kurihara 1999: figs 11.8, 11.13, 11.19; Zhang et al. 2018: 17, fig. 7.13, p. 18, figs 7.13-7.16; Ichinohe et al. 2018: fig. 2.B, C).