Rhynchozoon aff. rostratum ( Busk, 1856 )

Ramalho, Laís V., Taylor, Paul D., Moraes, Fernando Coreixas, Moura, Rodrigo, Amado-Filho, Gilberto M. & Bastos, Alex C., 2018, Bryozoan framework composition in the oddly shaped reefs from Abrolhos Bank, Brazil, southwestern Atlantic: taxonomy and ecology, Zootaxa 4483 (1), pp. 155-186 : 177-180

Rhynchozoon aff. rostratum ( Busk, 1856)

( Fig. 6D–F )

Rhynchozoon sp.: Reis et al., 2016: supplementary table.

Rhynchozoon rostratum: Bastos et al., 2018 : table 1.

Material examined. Abrolhos Bank, Bahia State, Brazil: MNRJ-Bry1338, Parcel dos Abrolhos, 15 m depth, February 2014, col. R. Moura, G. Amado-Filho & A . Bastos ; MNRJ-Bry1374, Parcel dos Abrolhos, 4 m depth, February 2014, col. R. Moura, G. Amado-Filho & A. Bastos.

Short description. Colonies encrusting, multilamellar; zooids initially orderly but becoming irregularly arranged. Frontal wall tuberculate with areolar pores only ( Fig. 6D ). Primary orifice with distinct rounded sinus, hidden by the development of the peristome; tubercles sometimes present, varying in number and size ( Fig. 6D, E ). Oral and frontal avicularia of similar shape and size, crossbar complete, the frontal avicularium triangular, diamond-shaped and distolaterally or laterally directed ( Fig. 6E ); oral avicularium single ( Fig. 6F ) directed laterally. Ovicells not observed.

Geographic distribution. Indonesia, E. Pacific, Caribbean and Gulf of Mexico ( Busk 1856; Winston & Heimberg 1986); Abrolhos Bank, Bahia State ( Reis et al. 2016; Bastos et al. 2018; present study).

Remarks. Rhynchozoon verruculatum ( Smitt, 1873) is very similar to R. rostratum , but it differs from the latter in having larger zooids, a shallow U-shaped sinus, more elongated diamond-shaped frontal avicularia, and ovicells that are completely immersed. Rhynchozoon brasiliensis Almeida et al., 2017 , also known from Bahia State, has a primary orifice with a V-shaped sinus, the peristomial avicularium is absent, and the frontal avicularium is variously oriented. Two other Brazilian Rhynchozoon species are distinct: R. coalitum Vieira et al., 2010 has only a suboral avicularium and lacks vicarious avicularia, while R. phrynoglossum Marcus, 1937 has large vicarious avicularia with truncate or tongue-shaped mandibles. The colonies found in the studied cores were poorly preserved, making a more precise identification difficult.

Figures

FIGURE 6. Scanning electron micrographs of three bryozoan species. A. Gemelliporina glabra, fragment showing orifices and a small avicularium. B, C. Plesiocleidochasma acuminata n. sp. B. General view of a fragment showing infertile zooids. C. Detail of some zooids showing cleithridiate orifices, a few scattered areolar pores and acuminate avicularia with rostra ending in a sharp and elongate tip. D–F. Rhynchozoon aff. rostratum. D. General view of a colony part showing some zooids with peristomial tubercles and frontal avicularia. E. Detail of some autozooids showing peristomial tubercles and frontal, triangular avicularia. F. Detail of one zooid showing distally beaded orifice and a suboral lateral avicularium with a triangular rostrum, and a suboral umbo.