Diplonotus supplicatus, Hayward & Winston, 2011

Hayward, Peter J. & Winston, Judith E., 2011, Bryozoa collected by the United States Antarctic Research Program: new taxa and new records, Journal of Natural History 45 (37 - 38), pp. 2259-2338 : 2286-2289

Family BIFAXARIIDAE Busk, 1884

Diplonotus supplicatus sp. nov.

( Figure 13 )

Material

Holotype. NMNH 1154036 : Eltanin cruise 22, station 1545, 61 ◦ 04’ to 61 ◦ 07’ S, 39 ◦ 55’ to 39 ◦ 42’ W, 2355–2897 m, 11 February 1966; fragment of colony comprising part of main axis, 10 mm long, 1.06 mm wide, with nine side branches, largest 4.4 mm; lacking proximal and distal portions, all branches broken short.

Paratypes. VMNH 013676.00: same data as holotype; six further fragments, the largest comprising part of a main axis, 6.25 mm long, with a complete lateral branch, 5 mm long, and broken stumps of four further branches .

Description

Colony erect, branching, developing an open, tree-like form; the main axis giving rise to stout lateral branches at irregular intervals, in alternating right/left sequence, or in opposite pairs, or in close succession along the same side; all branching in the same plane. In one of the paratype fragments one branch has initiated a second-order branch towards its tip. Autozooids in two alternating, back-to-back, longitudinal series, the arrangement apparent in newly budded autozooids at the branch tips, but obscured by thickening calcification in later ontogeny. Autozooids 0.65–0.75 mm long in frontal view; underlying spinocyst apparent at damaged branch tips; umbonuloid frontal shield initially regularly pitted, but more coarsely striated in later ontogeny, with few, scattered, marginal pores; the longitudinal median suture initially distinct but obscured by ontogenetic thickening. Peristomial aperture with moderately projecting, medially peaked, proximal lip, conspicuous in early ontogeny. Lateral oral avicularia paired, enclosed within peristome, rostrum facing frontally, directed distolaterally, with pronounced condylar processes and lacking a palate; mandible acute triangular. In later ontogeny both the autozooid apertures and the large avicularia become deeply immersed in thickening calcification, although, in the present material, they do not become completely occluded. Additional avicularia occur sporadically over the surface of the colony, very similar in size and shape to the lateral oral avicularia. Ovicell obscuring whole frontal surface of distally succeeding autozooid; ovoid, projecting markedly from the branch axis, its aperture opening into the peristome, bounded by a smooth lip; lateral oral avicularia of brooding zooids larger than those of autozooids. Large vicarious (?) avicularia distributed along each side of the branch, the extensive cystids obscuring the lateral portions of the autozooids; rostrum 0.25 mm long, projecting at almost a right angle from the branch axis, facing distally; rounded and slightly upturned distally, with pronounced condylar processes but no palate, mandible elongate, semi-elliptical.

Etymology

Latin, supplicatus : beseech, with reference to the outstretched, supplicant, appearance of the projecting avicularia.

Remarks

All described species of Bifaxariidae have been documented, and most have been described and figured, by Gordon (1988, 1993). Diplonotus supplicatus is distinguished from all previously described species by the large, distally facing avicularia that project from the long axis of the branch, their cupped rostra evoking the outstretched hands of a religious supplicant. Diplonotus was introduced by Canu and Bassler (1930) for D. costulatum , from two stations in the Galapagos Islands, at 40 and 684 fathoms depth (73 m and 1251 m, respectively), but most species subsequently ascribed to the genus have been collected from abyssal depths, and mostly from the Indo-west Pacific region. This new species marks the first record of the genus for the subantarctic southwest Atlantic.

Superfamily ARACHNOPUSIOIDEA Jullien, 1888 Family ARACHNOPUSIIDAE Jullien, 1888

Arachnopusia pelvicula sp. nov

( Figure 14 )

Material

Holotype. NMNH 1154030 : Hero cruise 691, station 20, 65 ◦ 35’ to 65 ◦ 37’ S, 67 ◦ 19’ to 67 ◦ 24’ W, 161 m, 8 February 1969; a single, multilaminar colony, forming a cylinder 21.25 mm long, investing an echinoid spine.

Description

Colony encrusting, multilaminar, thickly calcified. Autozooids large, rectangular, c. 0.80 mm long, but individual boundaries indistinct. Frontal shield typically with four (exceptionally three or five) large, equally sized foramina, occupying most of frontal surface, irregularly oval to almost circular, one or more occasionally with a short ligula projecting into its lumen. Aperture wider than long, its proximal edge with a low median umbo bearing a short, columnar avicularium. Apertural plate ( Figure 14B ) distinctive: transversely oval, 0.17–0.2 mm wide, deeply concave, thickly calcified, the proximal face coarsely ribbed, its rim toothed, the whole reminiscent of a stone water trough. A single lateral oral spine present, and a single lateral oral avicularium on the opposite side of the aperture, the rostrum directed proximally, its plane perpendicular to that of the apertural plate. Ovicell more or less spherical, with a narrow band of granular ectooecium bordering the aperture, bounded distally by a low ridge; submerged and largely obscured by a thickening ooecial cover, typically bearing three shortly columnar avicularia, only the granular entooecial lip remaining visible.

Etymology

Latin, pelvicula : little basin, with reference to the apertural plate.

Remarks

The specimen seems to have been alive when collected but most of the superficial lamina is missing, perhaps as a result of post-collection abrasion, and autozooids of the underlying, older, lamina show grossly thickened frontal shields, pierced by deep, cylindrical foramina, and lack spines, and all avicularia are damaged. However, sufficient parts of the youngest lamina remain to suggest that the avicularia were monomorphic, with a small rostrum less than 0.10 mm long, bearing a short, triangular mandible. No large avicularia were evident in any part of the colony.

This species most resembles Arachnopusia tristanensis Hayward and Thorpe, 1988 , from Tristan da Cunha, in which the frontal shield is pierced by four to seven large foramina. However, avicularia are much more numerous in that species and include an enlarged type with a broadly scaphoid rostrum up to 0.25 mm long, and the lateral oral avicularium is situated on the rim of the aperture, rather than within it, with the rostrum normal instead of perpendicular to the apertural plane .

Figures

Figure 13. Diplonotus supplicatus sp. nov., Holotype. (A) Part of branch to show ovicelled zooid (below) and an autozooid (top); (B) branch in lateral view, to show adventitious avicularia. Scale bars: 0.5 mm.

Figure 14. (A,B) Arachnopusia pelvicula sp. nov., Holotype. (A) Ovicelled zooids, centre and top left, with frontal shields of adjacent zooids, right and top; (B) detail to show subapertural plate. (C,D) Arachnopusia incernicula sp. nov., Paratype. (C) Group of ovicelled zooids; (D) detail to show subapertural plate in two zooids. Scale bars: 0.5 mm (A, D), 0.25 mm (C), 0.05 (B).