Rhynchozoon itaparicaensis n. sp.

(Figs 10A–F, 11A–D; Table 12)

Rhynchozoon verruculatum: CANU & BASSLER, 1928: P. 31, PL. 7, fIgS 2, 3.

Rhynchozoon verruculatum: VIEIRA et al., 2008: P. 33 (IN PART).

Rhynchozoon verruculatum: ALMEIDA et al., 2015A: P. 5 (IN PART).

NOT Cellepora verruculata: SMITT, 1873: P. 50, PL. 8, fIgS 170–172.

Material examined. Holotype: UFBA 1629, on valves of Pinctada imbricata. Paratypes: UFBA 1635, UFBA 1638, on valves of Pinctada imbricata, USNM 8564, Rhynchozoon verruculatum, F. Canu & R. Bassler det., Costa dos Coqueiros, Arembepe, Bahia, Brazil, coll. 1877 by Steamer Norseman.

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

Etymology. Alluding to the type locality, Itaparica.

Description. Colony encrusting, uni- to multilaminar. Zooids ovoid at growing edge (Fig. 10A), separated by low ridges, with 18–20 marginal pores. Autozooids (Figs 10B, 11A) strongly calcified, delimited by slightly raised lateral walls; frontal wall rugose, with small, rounded, scattered nodules, imperforate except for a single row of 12– 16 large, marginal pores. Primary orifice (Figs 10C, 11B) small relative to frontal shield length; broader than long, with 14–18 rounded denticles laterally and distally around margin; proximal edge with distinct, shallow, U-shaped median sinus; condyles small and triangular at proximal orificial corners. No oral spines. Primary orifice often obscured in peristome due to secondary calcification. Large suboral avicularium (Figs 10D, 11C) with well- developed chamber proximolateral to orifice on one side, with single cylindrical tubercle on opposite side, separated by U-shaped, laterally offset pseudosinus in secondary orifice; autozooids without large suboral avicularium may develop deep peristome with 3–4 rounded tubercles (often only 2 are distinct), obscuring primary orifice. Suboral avicularium with hooked rostrum, elongate-triangular mandible with curved edge, somewhat scimitar-like, with short uncinate process projecting into orifice. Frontal avicularia (Fig. 10A, E arrow) numerous, up to 4 per zooid (frequently 2), usually located at zooidal margin and directed distolaterally; rostrum diamond shaped, but sometimes with rounded proximal end; small to moderate in size, with complete crossbar. Ovicell (Figs 10F, 11D) hyperstomial, immersed with increasing calcification; ooecia subglobular and frontally flat, wider than long; ectooecium frontally uncalcified, leaving nearly semicircular tabula of exposed entooecium, with narrow labellum along proximal margin.

Remarks. Among Rhynchozoon species that have the primary orifice with a distinct, shallow, U-shaped median sinus, no oral spines, and large suboral avicularium, Rhynchozoon itaparicaensis n. sp. most closely resembles Rhynchozoon scimitar Dick & Grischenko, 2016, due the distinct scimitar-like shape of the suboral avicularium. Differences between R. itaparicaensis n. sp. and R. scimitar include the suboral sinus (deeper and narrower in R. scimitar); the shape of the condyles (triangular in R. itaparicaensis n. sp. but rounded in R. scimitar), the position of the suboral avicularium (immersed in the secondary orifice and with a short uncinate process in R. itaparicaensis n. sp.; at the secondary orificial margin and without uncinate process in R. scimitar); and the frequency of avicularia (zooids typically have a suboral avicularium and two frontal avicularia in R. itaparicaensis n. sp.; zooids have only one avicularium in R. scimitar, never a suboral and frontal at the same time).

Other Rhynchozoon species with the primary orifice and avicularia similar to those in R. itaparicaensis n. sp. are Rynchozoon documentum Hayward & Cook, 1983; Rhynchozoon fistulosum Hayward, 1993; Rhynchozoon ryukyuense Dick & Grischenko, 2016; and Rhynchozoon solitarium Tilbrook, 2006. However, whereas R. itaparicaensis n. sp. has a single suboral avicularium, scimitar-like, the suboral avicularium of R. documentum is subtriangular; R. fistulosum has two suboral avicularia; the suboral avicularium of R. ryukyuense varies from small and triangular to large and rectangular and that of R. solitarium is asymmetrically spatulate.

Canu & Bassler (1928) identified specimens from Bahia as Rhynchozoon verruculatum, however, it truly belong to R. itaparicaensis n. sp. (Fig. 11A–D). These two species differ in the number of oral tubercles (up to 4, but commonly 2, in Rhynchozoon itaparicaensis n. sp., 4–6 in R. verruculatum); the shape of the suboral avicularium (scimitar-like in R. itaparicaensis n. sp., diamond-shaped in R. verruculatum); and the number and shape of the frontal avicularia (up to 4, varying from drop-shaped to diamond-shaped in R. itaparicaensis n. sp., single and diamond-shaped in R. verruculatum).

Rhynchozoon itaparicaensis n. sp. is a common shallow water species at Bahia, frequently found on hard substrata such as shells and calcareous nodules (Canu & Bassler 1928).

Distribution. Atlantic: Brazil (Bahia).