Aulopocella americana, 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 : 38-40

Aulopocella americana n. sp.

( Figures 93–97 , Table 19)

Material examined. Holotype. MZUSP 0 358, Brazil, project REVIZEE South SCORE, RV ‘Prof. Wladimir Besnard’, station 6693. Paratypes. MZUSP 0 359, Brazil, project REVIZEE South SCORE, RV ‘Prof. Wladimir Besnard’, station 6678. MZUSP 0 360, station 6681. MZUSP 0361–0362, station 6693. Additional material. MZUSP 0 363, Brazil, project REVIZEE South SCORE, RV ‘Prof. Wladimir Besnard’, station 6661. MZUSP 0 364, station 6674. MZUSP 0 365, station 6678.

Diagnosis. Colony erect, with autozooids opening all around the axis. Frontal shield with a few minute pores along zooidal margins and around base of long peristome. Orifice deeply concealed at bottom of peristome, condyles scarcely apparent. No oral spines. Several small avicularia in peristomial rim of ovicelled zooids. Ovicell smooth, opening into peristome, the wall of which passes across the ovicell roof.

Etymology. The species name alludes to the first record of the genus from South America.

Description. Colony erect from a small attachment point of basally encrusting zooids. Small colonies unbranched, wider distally, hence narrowly claviform; large colonies (c. 30 mm high) branching outwards from the base or higher up, the branches of uneven diameter (2–3 mm), the longest dimension 24 mm. Zooids opening all around the axis, the main body of the zooid mostly recumbent, with the peristome angled outwards; zooids at the distal end of the colony more erect in orientation. Frontal shield smooth, with just a few very tiny areolar-septular pores in the margins and around the base of the peristome. In small fertile colonies (c. 5 mm high). Peristome elongated, tubular; at the apex of the axial (stem axis) side of the peristome is a small subtriangular avicularium with crossbar; beneath it a longitudinal ridge runs down the axial midline inside the shaft of the peristome; 1, rarely 2, other avicularia may be set in the rim of the peristome, neither associated with a descending ridge. Primary orifice deeply concealed at the bottom of the peristome, subcircular, with a broad shallow poster; condyles scarcely apparent. No oral spines. Frontally budded interzooidal and subvicarious avicularia of different sizes, the rostrum ranging from large and lingulate or hastate, to moderate-sized or small with a subacute rostrum; palatal foramen subtriangular or irregularly elongate, occupying less than half to two-thirds the rostral length; all such avicularia have a crossbar, the vicarious ones sometimes with a short columella. Ovicell globular, smooth, no tabula, opening into the peristome the wall of which passes across the roof of the ovicell, such that part of it is seen only within the peristome; 2–6 small avicularia in the peristomial rim of ovicelled zooids, the rostrum short, subacute; crossbar present. All the above characters are the same in larger colonies but secondary calcification, especially in older, proximal parts of colonies leads to peristomes appearing more recumbent and interzooidal avicularia more elongated, even columnar, and the vicarious avicularium may develop a more obvious columella on the crossbar. Ancestrula not seen.

n min–max mean SD Autozooid length 20 0.494–0.827 0.669 0.088 Autozooid width 20 0.247–0.420 0.295 0.042 Orifice length 20 0.105–0.148 0.127 0.015 Orifice width 20 0.105–0.136 0.123 0.009 Ovicell length 20 0.185–0.278 0.222 0.030 Ovicell width 20 0.216–0.290 0.247 0.021 Remarks. Aulopocella Maplestone, 1903 has been discussed most recently, and its status clarified, by Bock and Cook (2000), who included just three Australian species in the genus ― one Paleogene, one Neogene, and one Recent. Aulopocella americana n. sp. most closely resembles the oldest of the three, viz. the Late Eocene to Oligocene type species, A. tubulifera Maplestone, 1903 . Only small fertile colonies are known and these resemble small colonies of A. americana in having long peristomes with an apical avicularium associated with an internally descending peristomial ridge. The ovicells in both species are imperforate. The Brazilian species is the first in the genus to be recorded from South America (hence the specific name), achieves a larger size, and buds a variety of interzooidal avicularia .

Very small colonies of A. americana are claviform and usually attached in both Conescharellina cookae n. sp. and Conescharellina bocki n. sp. ( Fig. 93 ). Characteristic morphological differences are visible in large branching colonies with secondary calcification ( Fig. 97 ).

Distribution. Brazil: off São Paulo state, 99–430 m (present study).

Figures

FIGURES 93 – 97. Aulopocella americana n. sp., off São Paulo, Brazil (REVIZEE station 6693). 93, Small colony growing on Conescharellidae; 94, another colony found on Conescharellidae, 95, close-up of colony showing ovicelled zooids and autozooid with tubular peristome (bellow); 96, close-up of orifice and large interzooidal avicularia; 97, large colony with secondary calcification.