Rhynchozoon brasiliensis Almeida, Souza, Menegola & Vieira, 2017, n. sp.

Rhynchozoon brasiliensis n. sp.

(Figs. 84–89; Table 10)

Rhynchozoon rostratum: Souza 1989: 502; Machado & Souza 1994: 259. Rhynchozoon verruculatum: Almeida et al. 2015b: 5 (in part).

Material examined. Holotype: UFBA 1579, Todos os Santos Bay, 13°00’S, 38°32’W, 3–8 m, coll. 2013 (on sponge Callyspongia sp.). Paratypes: UFBA 1584, Camamu Bay, 13°53’S, 38°59’W, 18–20 m, coll. October 2012 (on sponge Haliclona (Soestella) melana); UFBA 1189, Camamu Bay, 13°53’S, 38°59’W, 18–20 m, coll. October 2012 (on sponge Bubaris sp.); UFBA 2340, Camamu Bay, 13°53’S, 38°59’W, 18–20 m, coll. October 2012 (on sponge Bubaris sp.).

Type locality. Todos os Santos Bay, Bahia State, NE Brazil.

Etymology. Alluding to the type locality in Brazil.

Description. Colony encrusting, uni- to multilaminar. Zooids at the growing edge polygonal, rectangular to hexagonal; primary orifices often with a single prominent proximo-lateral tubercle, and with a rhombic suboral avicularium directing distolaterally, with complete crossbar. In later astogeny the autozooidal frontal shield thickens and the peristome develops 4–6 tubercles, generally two distal and three proximal ones, obscuring the primary orifice and suboral avicularium. Autozooids almost indistinct, limited by slightly raised lateral walls. Frontal shield with tubercular processes, imperforate except by a single row of 10–16 large marginal pores.

Primary orifice small relative to zooidal length, the circular distal edge with 12–20 rounded denticles, the proximal edge with a deep and broadly V-shaped sinus; condyles small at proximal corners of the orifice. No oral spines. Peristome well-developed and frequently obscuring the primary orifice, formed by solid tubercles that become indistinct in later astogeny. Frontal avicularia sometimes absent in young zooids, but numerous and irregularly scattered throughout the colony, placed near zooidal margins; outline rhombic, small, with complete crossbar, rostrum elongate triangular. Ovicells prominent in young zooids, becoming immersed with increasing calcification; ooecia subglobular and frontally flat, endooecium completely calcified, ectooecium frontally uncalcified, with almost circular tabula, completely bordered by endooecium along the proximal margin; ooecia often covered by tubercular secondary calcification of the frontal shields of surrounding zooids along the lateral and distal margins.

Remarks. Rhynchozoon brasiliensis n. sp. resembles Rhynchozoon fistulosum Hayward, 1993, Rhynchozoon incrassatum (Hincks, 1882) and Rhynchozoon papuliferum Souto, Kaufmann & Canning-Clode, 2015 in having a primary orifice with a distinct sinus, no oral spines and vicarious avicularia, frontal and zooidal avicularia with similar shape and size, and immsersed ovicells (in later astogeny) with exposed ooecial tabula. Rhynchozoon fistulosum is distinguished in having a shallow sinus (deep in R. brasiliensis n. sp.), a primary orifice that is wider than long (often longer than wide in R. brasiliensis n. sp.), smooth frontal calcification (with wart-like processes in R. brasiliensis n. sp.) and a single frontal avicularium (numerous in R. brasiliensis n. sp.). Rhynchozoon incrassatum is distinct in having a suboral avicularium placed on a well-developed calcified camara (absent in R. brasiliensis n. sp.) and a single frontal avicularium placed at the center of the frontal shield (numerous and marginal in R. brasiliensis n. sp.). Rhynchozoon papuliferum is distinguished from R. brasiliensis n. sp. in having many marginal pores (few in R. brasiliensis n. sp.), a primary orifice that is not obscured by the peristome (in R. brasiliensis n. sp. the peristome embeds the orifice), and the ectooecium is somewhat triangular in shape (almost circular in R. brasiliensis n. sp.).

Although Souza (1989) and Machado & Souza (1994) recognized this species as Rhynchozoon rostratum (Busk, 1856), we analysed specimens studied by them (uncatalogued specimens deposited at UFBA) and conclude that they truly belong to R. bransiliensis n. sp. Differences between R. rostratum and R. brasiliensis n. sp. include the primary orifice (with a distinct rounded sinus in R. rostratum and almost V-shaped in R. brasiliensis n. sp.), frontal avicularia (distolaterally directed in R. rostratum and with no defined orientation in R. brasiliensis n. sp.), and a subtriangular to oval ooecial tabula (in R. brasiliensis n. sp. the tabula is almost circular). Almeida et al. (2015) also misidentified some specimens of R. brasiliensis n. sp. as Rhynchozoon verruculatum (Smitt, 1873), but R. verruculatum has a semicircular primary orifice with a shallow broad sinus (orifice circular and sinus almost Vshaped in R. brasiliensis n. sp.), and large diamond-shaped avicularia below and beside the peristome (absent in R. brasiliensis n. sp.). Since Souza (1989) and Machado & Souza (1994) were the only ones to report R. rostratum from Brazil, we conclude that this species does not occur in Brazilian waters, as already suggested by Vieira et al. (2010).

Species of Rhynchoozoon are commonly found in coral reefs, on shells and other hard substrata (e.g., Marcus 1938, 1939; Osburn 1952; Winston 1986). Large colonies of R. brasiliensis n. sp. were found attached to the rugose-textured sponge Callyspongia sp.

Distribution. Atlantic: Brazil (Bahia).