Stephanollona arborescens, Vieira, Leandro M., Gordon, Dennis P., Souza, Facelucia B. C. & Haddad, Maria Angélica, 2010

Vieira, Leandro M., Gordon, Dennis P., Souza, Facelucia B. C. & Haddad, Maria Angélica, 2010, New and little-known cheilostomatous Bryozoa from the south and southeastern Brazilian continental shelf and slope, Zootaxa 2722, pp. 1-53 : 37

Stephanollona arborescens n. sp.

( Figures 87–92 , Table 18)

Material examined. Holotype. MZUSP 0 346, Brazil, project REVIZEE South SCORE, RV ‘Prof. Wladimir Besnard’, station 6661. Paratypes. MZUSP 0 347, Brazil, project REVIZEE South SCORE, RV ‘Prof. Wladimir Besnard’, station 6661. MZUSP 0 348, station 6676. MZUSP 0 349, station 6678. MZUSP 0 350, station 6681. Additional material. MZUSP 0 351, Brazil, project REVIZEE South SCORE, RV ‘Prof. Wladimir Besnard’, station 6661. MZUSP 0 352, station 6662. MZUSP 0 353, station 6665. MZUSP 0 354, station 6666. MZUSP 0 355, station 6673. MZUSP 0 356, station 6678. MZUSP 0 357, station 6816.

Diagnosis. Colony erect, bilaminar, bifurcating, surface coarse-textured. Six oral spines; orificial sinus narrowest distally, the condyles encroaching on the sinus entrance. Avicularia comprising rare, almost parallel-sided elongate forms and one or a pair of rounded lateral-oral avicularia serrated rostral rim. Ovicell subglobular, hyperstomial, smooth-surfaced with a short labellum and lateral indentations.

Etymology. The species epithet arborescens alludes to the erect, branching, bilaminar colony form.

Description. Colony primarily encrusting, unilaminar, becoming erect, bilaminar. Zooids irregularly polygonal; frontal shield thick and rough-textured, imperforate except for a few small marginal pores. Orifice rounded, beaded distally, with two large condyles encroaching on opening of narrow sinus. Oral spines 6, articulated, sometimes obscured in later ontogeny; ovicelled zooids with paired lateral spines. Large avicularia rare, usually at the base of the colony; the rostrum almost straight-sided to slightly tapering distally, with rounded distal tips; crossbar complete, lacking a columella; rostral palate partially incomplete, with triangular window; the mandible elongate, tapering, with a rounded tip. Small avicularia rounded, placed proximolateral to orifice, orientated proximolaterally, crossbar complete, aligulate, with minutely serrated rostrum. With increasing calcification, zooids often develop a suboral protuberance bearing a small avicularium. Ovicell globular, hyperstomial, subimmersed in later ontogeny, ectooecium incomplete frontally, with large frontal excavation and exposed endooecium, aperture with short wide labellum.

n min–max mean SD Autozooid length 20 0.346–0.667 0.468 0.076 Autozooid width 20 0.259–0.445 0.346 0.048 Orifice length 20 0.080–0.111 0.094 0.009 Orifice width 20 0.093–0.117 0.103 0.007 Ovicell length 20 0.148–0.216 0.172 0.024 Ovicell width 20 0.154–0.241 0.200 0.020 Remarks. The general appearance of colonies of Stephanollona arborescens n. sp. resembles that of Cigclisula arborescens , with very different zooidal features. Some shared characters are found in both species of Stephanollona described here, but the two species may be distinguished by proportionately larger avicularia in S. angusta , the size and position of the small rounded avicularia (lateral in S. angusta and slightly smaller and laterodistal or suboral in S. arborescens ), the rostrum of the small avicularia (smooth in S. angusta , serrated in S. arborescens ) and the shape of the excavation in the ectooecium, smaller and rounded in S. angusta . Spine bases are closer together in S. arborescens .

Distribution. Brazil: off São Paulo and Rio Grande do Sul states, 99–366 m (present study).

Figures

FIGURES 87 – 92, Stephanollona arborescens n. sp., MZUSP 349 (part of the paratype specimen), off São Paulo, Brazil. 87, Colony with some large avicularia; 88, colony with some ovicelled zooids; 89, close-up of large avicularia; 90, some ovicelled zooid; 91, close-up of ovicelled zooid with large rounded pore; 92, close-up of orifice with six oral spines.