Stephanollona domuspusilla Ramalho & Moraes, 2021

Ramalho, Laís V., Moraes, Fernando C., Salgado, Leonardo T., Bastos, Alex C. & Moura, Rodrigo L., 2021, Bryozoa from the reefs off the Amazon River mouth: checklist, thirteen new species, and notes on their ecology and distribution, Zootaxa 4950 (1), pp. 1-45 : 23-26

Stephanollona domuspusilla Ramalho & Moraes n. sp.

( Figs 11D, E; 12A, B)

Material examined. Holotype: MNRJBRY-1543: Brazil, Amapá state (Sta #3, 03°35.4267’N – 049°07.6028’W), 90 m, on sponge, 26 September 2014, collected by Fernando Moraes & Rodrigo Moura (NHo Cruzeiro do Sul ).

Etymology. From the Latin noun domus (meaning home) plus the adjective pusilla, - us, - um (meaning small), referring to the small size of the zooids.

Diagnosis. Autozooids with tubercular, imperforate frontal shield; 5–7 oral spines, the most proximal pair lanceolate; orifice with distal border denticulate and U-shaped sinus constricted by small lateral teeth; condyles projecting beyond the sinus border. Two kinds of adventitious avicularia: small, single and rounded suboral avicularium with serrated rostrum, and another large, elongate avicularium, triangular with rounded tip, placed laterally.

Description. Colony encrusting, multiserial, uni- to multilaminar ( Fig. 11D). Autozooids small, oval to irregularly polygonal, longer than wide [L 317–369–441 (SD 35, N 11); W 242–302– 360 µm (SD 42, N 11)]; frontal shield tubercular, imperforate except for some (5–7) scattered medium to large sized [14–24– 39 µm diameter (SD 6, N 27)], rounded, marginal areolar pores ( Figs 11D, E, 12A, B). Orifice cleithridiate, longer than wide [L 116–133–147 (SD 10, N 11); W 101–111– 118 µm (SD 7, N 11)], with 5–7 (usually six) hollow spines [13–26– 35 µm diameter (SD 6, N 17)], four visible in ovicellate zooids; the most proximal pair of spines lanceolate, the others spear-shaped with irregular calcification ( Figs 11E, 12A, B); distal border denticulate with 14–18 small beads; U-shaped sinus constricted by small lateral teeth; two long downward facing condyles projecting beyond the sinus border ( Figs 11E, 12A, B); one zooid with a broader and shallower sinus observed ( Fig. 11E). Two types of avicularia: (1) single, small [L 42–57– 73 µm (SD 10, N 7)], rounded avicularium placed suborally (rarely laterally) and oriented laterally, usually inclined in respect to the frontal wall; rostrum rounded, serrated, and crossbar complete without columella ( Figs 11E, 12A, B); (2) single large, elongate [L 187–203– 219 µm (SD 16, N 3)], somewhat triangular avicularium, placed laterally to orifice; rostrum triangular with rounded and slightly hooked tip, slightly curved to one side; crossbar complete without columella ( Figs 11E, 12A). Ovicell hyperstomial, wider than long [L 146–149–151 (SD 4, N 2); W 181–186– 191 µm (SD 7, N 2)], with smooth ooecial surface similar to the zooidal frontal wall ( Fig. 12B).

Remarks. The two most similar species recorded in Brazil are Stephanollona arborescens Vieira et al., 2010b and S. angusta Vieira et al., 2010b . The former species has the same small, rounded avicularium and six spines, but differs from S. domuspusilla Ramalho & Moraes n. sp. in having larger zooids (L 346–468–667, W 259–346– 445 µm), smaller orifice wider than long (L 80–94–111, W 93–103– 117 µm), condyles encroaching on the sinus (in the new species the condyles slightly surpass the opening), small avicularium usually proximo-laterally placed and proximo-laterally directed (in the new species the avicularium is suboral and laterally directed), and occasionally elongate avicularia rarely associated with the orifice (while in the new species it is lateral to orifice), and the rostrum is not hooked and the lateral margins are almost straight (see fig. 87, 89 in Vieira et al. 2010b). Stephanollona angusta has two or more avicularia per autozooid, small, rounded avicularium with smooth rostrum placed proximolaterally to the orifice or proximally to the large avicularia. Stephanollona boreopacifica Yang et al., 2018b from Korea, resembles the new species in having U-shaped sinus and rounded small avicularia with serrated borders, but can be distinguished by the narrower orifice (L 103–138, W 70–85 µm), and wider, more elongate avicularia associated with the ovicell ( Yang et al. 2018b).

Several species included in Stephanollona have broad, shallow orificial sinus, a feature characteristic of Stephanollina Vigneaux, 1949 , previously a subgenus of Stephanollona , that Gordon (2006) suggested to elevate to the rank of genus in the new family Sfeniellidae Gordon, 2006 . More recently, Di Martino & Taylor (2017) followed Gordon’s (2006) suggestions and included Stephanollina in Sfeniellidae modifying both the diagnoses of the family and of the genus Stephanollina , selecting Stephanollina dentata as the type species. Based on this, species of Stephanollona with shallow sinus must be reviewed.