Genus Calyptotheca Harmer, 1957

Calyptotheca Harmer, 1957: 1008; Cook 1965: 436; Tilbrook 2006: 219; Reverter-Gil, Souto & Fernández-Pulpeiro 2012: 4.

Type species. Schizoporella nivea var. wasinensis Waters, 1913, by original designation as Calyptotheca wasinensis (Waters, 1913) .

Diagnosis. Colony encrusting, or forming unilaminar cones or erect anastomosing networks of tubes or wavy plates, bilaminar or unilaminar, from an encrusting base. Frontal shield densely pseudoporous, autozooids separated by grooves, sutures, areolar-septular pores separately distinguishable or otherwise. Lateral walls with conspicuous septular pores.

Primary orifice rounded, oval or pyriform, with a proximal sinus and conspicuous proximolateral condyles; inner edge of anter with a lunula. Oral spines absent. Adventitious avicularia suboral, lateral-oral or marginal. Large, infrequent vicarious avicularia in some species.

Ovicell globose, hyperstomial (prominent) to immersed, resting upon or partially embedded in the frontal shield of the distal zooid, cleithral; pseudoporous, secondary calcification resembling the pseudoporous frontal shield; often cormidial, with raised lines of calcification separating sectors. Conspicuous orificial dimorphism in some species, with ovicellate orifices wider and with a shallower sinus than non-ovicellate orifices. Ancestrula tatiform, with spines.

Remarks. Calyptotheca is distinguished by a regularly pseudoporous frontal shield, orificial sinus with proximolateral condyles and globose ovicells that are pseudoporous like the frontal shield.

Of the three other lanceoporid genera, Stephanotheca Reverter-Gil, Souto & Fernandez-Pulpeiro, 2012 is most similar to Calyptotheca and the clearest distinguishing character is the ovicell; that of Stephanotheca is ‘crowned’, having a circular or semicircular nodular ridge of calcification surrounding the central perforations, whereas the ovicells of Calyptotheca are evenly perforated. Lanceopora d’Orbigny, 1851 is free-living, with erect, stalked and rooted bilaminar colonies, and Emballotheca Levinsen, 1909 lacks a distinct sinus and has proximally downturned condyles. Lanceoporids typically, but not universally, also have cormidial secondary calcification of the ovicell, i.e. involving (originating from) more than one zooid.

Calyptotheca superficially resembles Metroperiella Canu & Bassler, 1917, which also has a densely pseudoporous frontal shield and an orificial sinus with proximolateral condyles. Metroperiella differs from Calyptotheca in having pointed, proximally downturned condyles, lappets (thin, raised, lateral orificial margins) and ovicells with perforations with raised rims that do not resemble those of the frontal shield, and a bordering rim of calcification in at least some species (see M. inaequalis [in Tilbrook 2006, p. 183, pl. 39E, F, as M. circumflexa], and M. agassizi Winston & Woollacott, 2009, p. 266, fig. 21).

Species of Calyptotheca are distinguished by the size and shape of the primary orifice, the shape and ornamentation of the condyles, the position, shape, size and orientation of adventitious avicularia and the presence of vicarious avicularia. Ovicells vary in the degree of immersion in the frontal shield of the distal zooid, some being recumbent (resting upon the surface) with others subimmersed or fully immersed. The form of cormidial secondary calcification may also vary—some species have Y-shaped suture lines, indicating contributions from three adjacent zooids. The lunula, a narrow ledge of calcification lining the distal rim, upon which the operculum rests (Harmelin et al. 1989; Tilbrook 2006), is restricted to the distal edge of the orifice in some species and in others continues laterally, appearing to be continuous with the condyles. It has not previously been used as a diagnostic character.

Orificial dimorphism, with ovicellate orifices wider than autozooid orifices, is an obvious feature in some Calyptotheca species only. All five of the species described below in which ovicells were found (the small colony of C. triquetra did not have ovicells) are dimorphic but it is only slight in three species while substantial enough to be obvious under light microscopy for two species, C. conica and C. wasinensis .