Atlantisina gorringensis, Berning & Harmelin & Bader & Cibio, 2017

Berning, Björn, Harmelin, Jean-Georges & Bader, Beate, 2017, New Cheilostomata (Bryozoa) from NE Atlantic seamounts, islands, and the continental slope: evidence for deep-sea endemism, European Journal of Taxonomy 347, pp. 1-51 : 26-28

Atlantisina gorringensis gen. et sp. nov.

urn:lsid:zoobank.org:act:7E59E329-59B0-496B-ACE5-63C4350AD88D

Fig. 9 A–E, Table 9

Diagnosis

Zooids comparatively small, frontal shield with a reticulate pattern of raised ridges encircling round to polygonal depressions, the longitudinal ridges often more pronounced than the transversal ones, shield distolaterally raising to form a large and slightly flaring collar that is equipped with up to eight short pointed mucrones, the lateral pair usually pointing distally; lateral walls reduced, septular pores therefore relatively small and elongated, the distal pore large and suborbicular. Orifice comparatively small, orbicular, with a straight proximal margin, as long as wide, short condyles thickened and rounded, orifice margin with six spines. Ectooecium relatively extensive, covering approximately two-thirds of ooecium; endooecial surface as frontal shield, exposed area narrowing proximally. Ancestrula tatiform, opesia slightly constricted distally.

Etymology

Named after its type locality, Gorringe Bank.

Material examined

Holotype

GORRINGE BANK: 1 colony on shell, Stn 17 ( MNHN-IB-2014-70 ).

Paratype

GORRINGE BANK: 1 colony on shell, Stn 17 ( OLL 2016/147).

Other material examined

GORRINGE BANK: 2 small colonies on pebble, Stn 18 (unregistered MNHN material).

AMPÈRE SMT: 2 colonies on rocks, Stn 1 (unregistered MNHN material).

Description

Colony encrusting, unilaminar, forming small patches and bi- to triserial ribbons ( Fig. 9A ). Zooecia distinctly smaller than in other species of Atlantisina gen. nov., oval, separated by deep grooves and a thin ridge ( Fig. 9 B–C). Frontal shield convex, surface with a reticulate pattern of raised ridges encircling round to polygonal depressions, occasionally longitudinal ridges more pronounced than lateral ones ( Fig. 9 B–D), imperforate except for a few small marginal pores hardly visible in frontal view or in older zooecia; proximolateral suboral area framed by a tall, steeply rising and slightly flared collar, marginally abutting proximal pair of spines, crest of collar with some six short, pointed mucrones, outer pair longer and pointing distally ( Fig. 9 B–D); smooth gymnocystal calcification forming distal and terminal part of collar is clearly demarcated from proximal reticulate pattern of cryptocystal-type frontal shield by a distinct suture; lateral walls moderately well developed, (disto)lateral septular pores elongated, area of cryptocystal-type calcification surrounding pores reduced to a thin lining; distal ooecial pore large, suborbicular.

Orifice distinctly smaller in than other species of Atlantisina gen. nov., suborbicular, as long as broad, widest at about mid-distance, proximal border fairly straight, proximal fourth delimited by a pair of very short, thickened and rounded condyles ( Fig. 9E ); distolateral margins equipped with six whip-like spines with thick bases, arranged in two groups of three with a distinct distal gap; all six spines present in ovicellate zooids with distal pair closely appressed to proximolateral ooecium wall.

Ovicell hyperstomial, ooecium barely resting on distal zooid’s frontal shield, a laterally compressed sphere, longer than broad, with a short tubular peristome wedged in between distalmost pair of spines and opening at distal orifice margin, ooecial aperture orbicular, acleithral ( Fig. 9C ); smooth ectooecium covering about two-thirds of ooecium; exposed endooecium reduced to centre, narrowing proximally, surface topography similar to frontal shield but with narrower elongated depressions.

Ancestrula tatiform, constricted in distal part, first generation autozooid budded distally or distolaterally ( Fig. 9B ).

Remarks

This species differs from its closest allies, Atlatisina lionensis gen. et sp. nov. and A. acantha gen. et sp. nov. (see below), in that the longitudinal ridges on the frontal shield are sometimes more pronounced than the transversal ones, occasionally giving the surface a striped appearance instead of a honeycomb structure. Moreover, the condyles are distinctly thickened in A. gorringensis gen. et sp. nov., and the suboral crest is equipped with six to eight relatively short mucrones of almost equal lengths (only the distolateral ones may be slightly longer). The crest is also distinctly curved around the proximolateral orifice in this species, instead of being rather straight as in A. lionensis gen. et sp. nov., but does not reach quite as far distally, and is not as thickly calcified, as in A. acantha gen. et sp. nov. Finally, A. gorringensis gen. et sp. nov. has distinctly smaller zooids and orifices than all other species in this genus ( Table 9).

Ecology

The bi- to triserial colonies encrust small rocks and shells at depths of 180 to 330 m.

Distribution

Atlantisina gorringensis gen. et sp. nov. occurs on Gorringe Bank and Ampère Smt.

Figures

Fig. 9. Atlantisina gorringensis gen. et sp. nov., Gorringe Bank. A. Overview of holotype (MNHN- IB-2014-70). B. Periancestrular region, the constricted oral region of the partly overgrown ancestrula is to the left (paratype OLL 2016/147). C. Two ovicellate zooids, the lower one with a well-preserved suboral crest (MNHN-IB-2014-70). D. The same zooid in lateral view (MNHN-IB-2014-70). E. Closeup of orifice (OLL 2016/147). Scale bars: A = 500 µm; B = 300 µm; C–D = 100 µm; E = 50 µm.