Calyptotheca triangulata Almeida & Souza & Farias & Alves & Vieira 2018, n. comb.

Calyptotheca triangulata (Canu & Bassler, 1928) n. comb.

(Fig. 7A–F; Table 8)

Cribella triangulata CANU & BASSLER, 1928: P. 82, PL. 4, fIg. 10.

Escharina krampi: MARCUS, 1939: P. 138, PL. 4, fIg. 12.

Calyptotheca tenuata: HARMER, 1957: P. 1016 (PART), PL. 68, fIgS 16, 17.

Cribellopora triangulata: VIEIRA et al., 2008: P. 31.

Calyptotheca tenuata: CUMMINg & TILBROOK, 2014: P. 160, fIg. 5.

? Escharina krampi: MARCUS, 1937B: P. 216, fIg. 17A–C.

Material examined. UFBA 1624, UFBA 3354–3356, on valves of Pinctada imbricata.

Comparative material: USNM 8553, Cribella triangulata, holotype, F. Canu & R. Bassler det., Todos os Santos Bay, Bahia, Brazil, coll. 1876 by Richard Rathbun.

Redescription. Colony encrusting (Fig. 7A, E), unilaminar. Autozooids (Fig. 7B, E) subquadrangular to hexagonal, delineated by raised lateral walls. Frontal wall perforated by large pseudopores, sometimes absent below the orifice in older zooids; marginal pores frequently elongate, slightly larger at zooidal corners. Primary orifice (Fig. 7C, D) transversely oval, wider than long, with two small, rounded proximolateral condyles and broad, shallow sinus; narrow shelf inside distal margin of peristome (here referred to as a ‘lunula’, following Cumming & Tilbrook 2014). Primary orifice with a raised, thickened, crescent nodular ridge proximally and laterally. Zooids bear single frontal avicularium (often absent), proximolateral to orifice, pointing proximomedially (Fig. 7C) or distomedially (Fig. 7D); rostrum rounded proximally, long-triangular distally, foramen subcordate, occupying approximately one-third of avicularium length, palate semicircular, with median pore. Ovicell (Fig. 7A, F) hyperstomial; ooecium globose, covered with pseudopores similarly to frontal wall; secondary calcification cormidial (i.e. with Y-shaped sutures of calcification, see arrow in Fig. 7F), closed by zooidal operculum. No orifice dimorphism.

Remarks. The generic placement of this species is historically controversial. It was originally described in the genus Cribella Jullien & Calvet, 1903, which lacks diagnostic morphological characters and whose identity is doubtful (Canu & Bassler 1927; Harmer 1957). Marcus (1939) later misidentified specimens from São Paulo (SE Brazil) as Escharina krampi Marcus, 1937b, originally described from Santa Helena (Marcus, 1937b). However, the Brazilian specimens (Marcus, 1939; present study) clearly do not belong to Escharina Milne Edwards, 1836, since they have a pseudoporous frontal wall, no oral spines, and porous ooecia. Vieira et al. (2008) reassigned it to Cribellopora Gautier, 1957 species that have an imperforate frontal wall, oral spines and narrow orificial sinus. Specimens from Bahia found on shells of Pinctada imbricata (Fig. 7A–D) fit all characters of the holotype (Fig. 7E–F), which is also from Todos os Santos Bay, Bahia (Canu & Bassler 1928).

Morphological characters observed in the holotype and in additional material from Bahia—i.e. pseudoporous frontal wall, primary orifice with distal lunula, proximal sinus and prominent lateral condyles, absence of oral spines, and pseudoporous ovicell with cormidial secondary calcification—allow us to formally reassign Cribella triangulata Canu & Bassler, 1928 to Calyptotheca Harmer, 1957 (acc. Cumming & Tilbrook 2014; Cumming 2015).

Among Calyptotheca species worldwide, Calyptotheca tenuata Harmer, 1957, originally described from Indonesia, is morphologically and morphometrically indistinguishable from C. triangulata n. comb. (Harmer 1957; Cumming & Tilbrook 2014). As stated by Cumming & Tilbrook (2014), Calyptotheca tenuata is diagnosed by having relatively large dimensions of zooids and pseudopores, primary orifice oval and with wide shallow sinus and acuminate basally curved avicularia. All these characters fit specimens originally studied by Canu & Bassler (1928) and additional material studied here. In this sense, following the principle of priority of ICZN (1999, Art. 23), Calyptotheca tenuata Harmer, 1957 is here considered a junior synonym of Cribella triangulata Canu & Bassler, 1928.

Under the name Calyptotheca tenuata, C. triangulata n. comb. was already reported from Indonesia, Australia and China (Liu et al. 2001; Cumming & Tilbrook 2014). The unusual geographic distribution and difficulties in traditional morphologic-morphometric distinction between specimens from the Indo-Pacific and the Atlantic oceans suggest that C. triangulata n. comb. could be a widespread cryptogenic species (with unknown natural origin). Although having coronate short-lived larvae (not allowing long-range dispersal), some cheilostome bryozoans are known to occur in different geographic locations in all oceans and sometimes related with bioinvasion events (e.g. Harmelin et al. 2012; Almeida et al. 2017b; Miranda et al. 2018). On the other hand only integrative approaches, including both morphological and genetic analyses of C. triangulata n. comb., will allow to infer if this species is cryptic, exotic and/or invasive in some localities (Harmelin et al. 2012; Miranda et al. 2018).

At least two other species of Calyptotheca are known from Brazil, C. ornatissima (Canu & Bassler, 1928) and C. vaginata (Canu & Bassler, 1928). Calyptotheca ornatissima is readily distinguished from C. triangulata n. comb. in having four types of avicularia (suboral, other frontal, lateral and vicarious) and dimorphic orifices (wider in ovicelled than in non-ovicelled autozooids). No avicularia are known to occur in C. vaginata (teardrop-shaped avicularia occur in C. triangulata n. comb.), which also has hexagonal autozooids (subquadrangular in C. triangulata n. comb.) with a broader orificial sinus than in C. triangulata n. comb.

Calyptotheca triangulata n. comb. is frequently found on hard substrata, including shells and stones (Marcus 1939).

Distribution. Western Atlantic: Brazil (Bahia and São Paulo) (Vieira et al. 2008); Indo-Pacific: Indonesia,

Australia and China (Cumming & Tilbrook 2014).