Atlantisina lionensis, 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 : 23-25

Atlantisina lionensis gen. et sp. nov.

urn:lsid:zoobank.org:act:54D46F97-6F57-41D2-9417-51DA064B3DF5

Figs 1A , 7 A–D, 8, Table 8

Diagnosis

Frontal shield with a reticulate pattern of raised ridges around polygonal depressions; orifice suborbicular, condyles short and without thickened tip; suboral region with a broad band of gymnocystal calcification forming a tall, relatively planar or slightly arched crest carrying three to five pointed mucrones of variable size and shape, the central ones shorter and vertically oriented, the two lateral ones longer and directing distolaterally; lateral walls moderately well developed, septular pores transversely oval to very elongate, area surrounding the pores reduced to absent, distal pore comparatively large, suborbicular, slightly raised relative to lateral ones; orifice margin with six oral spines. Ooecium slightly longer than wide; ectooecium relatively broad, covering about two-thirds of ooecium; exposed endooecium relatively small, imperforate, surface topography similar to that of frontal shield but with elongated depressions and steeper ridges; ooecial peristome relatively short. Ancestrula with 11 spines (four oral, seven mural).

Etymology

Named after its type locality, Lion Smt.

Material examined

Holotype

LION SMT: the ovicellate colony marked ‘H’, plus 3 smaller colonies, on a pebble of volcanic rock, Stn 36 ( MNHN-IB-2014-66 ).

Paratypes

LION SMT: 1 coated colony, Stn 36 (MNHN-IB- 2014-67); 2 colonies on a pebble, Stn 36 (MNHN- IB- 2014-68); 7 colonies and 1 ancestrula on a pebble, Stn 36 (MNHN-IB- 2014-69).

Other material examined

LION SMT: ca 20 colonies on rocks, Stn 36 (unregistered MNHN material); 10 colonies on two pebbles, Stn 36 ( OLL 2016/146).

SEINE SMT: 1 colony on limestone, Stn 43 (unregistered MNHN material).

Description

Colony encrusting, unilaminar, forming small patches and/or bi- to triserial ribbons ( Fig. 7A ). Zooecia roughly oval, with tapering proximal end(s) wedged in between proximal zooecia, separated by deep grooves. Frontal shield convex, surface with a reticulate pattern of raised ridges around polygonal depressions, imperforate except for a few small (although comparatively conspicuous) marginal pores faintly visible in frontal view ( Fig. 1A ); a tall, broad and moderately curved or planar suboral crest is formed predominantly by smooth gymnocystal calcification, sloping distolaterally and abutting proximal pair of spines, generally with two long, pointed lateral mucrones directing distolaterally that may occasionally bear tiny secondary mucrones, and one to three smaller central mucrones pointing vertically ( Figs 1A , 7 B–D); lateral walls moderately well developed laterally, more extensive in distal part, lateral septular pores transversely oval to extremely elongate, area surrounding pores reduced to absent ( Figs 1A , 7 B–D); distal pore comparatively large, suborbicular and slightly raised relative to lateral ones.

Orifice orbicular, widest at about mid-distance, proximal border fairly straight to slightly concave, proximal third delimited by a pair of short, blunt condyles, tips usually not thickened ( Fig. 7B ); distolateral margins with six thick spines arranged in two groups of three with a distinct distal gap; all six spines present in ovicellate zooids with distal pair abutting proximolateral ooecial wall and flanking ooecial aperture on both sides.

Ovicell hyperstomial, ooecium barely resting on frontal shield of distal zooid, globular, slightly longer than wide, with a very short tubular peristome opening at distal orifice margin ( Figs 1A , 7 B–D); ectooecium relatively broad, covering about two-thirds of ooecium; exposed endooecium relatively small, surface topography similar to that of frontal shield but with steeper ridges delimiting smaller elongated concavities; ooecial aperture slightly taller than wide, acleithral.

Only ancestrula observed has 11 long and thin spines with four oral ones that are oriented vertically and seven mural ones that bend over opesia.

Remarks

The high morphological plasticity of the suboral crest in Atlantisina lionensis gen. et sp. nov., with a great variability in the number and shape of the mucrones occurring even within the same colony ( Fig. 8 ), is a typical feature of this species. However, with two prominent lateral mucrones pointing in distal directions and shorter intermediate ones, the shape of the suboral crest of A. lionensis gen. et sp. nov. is in general similar to that of A. tricornis gen. et sp. nov., and also to the even larger ones in A. gorringensis gen. et sp. nov. and A. acantha gen. et sp. nov. (see below).

Ecology

The bi- to triserial colonies of Atlantisina lionensis gen. et sp. nov. were recovered from depths between 320 and 630 m, encrusting small rocks.

Distribution

The species occurs on the Lion and Seine seamounts.

Figures

Fig. 1. Morphological characteristics of Atlantisina gen. nov. A. The kenozooidal ooecium of Atlantisina lionensis gen. et sp. nov. in lateral view (paratype MNHN-IB-2014-67), showing the broad band of ectooecium and the centrally exposed endooecium; note that the suboral crest is formed by smooth gymnocyst whereas the remaining frontal shield is cryptocystidean. B. Distal view of an autozooid of Atlantisina meteor gen. et sp. nov. showing two distolateral communication pores and the slightly raised central pore from which the ooecium is budded (paratype MNHN-IB-2014-50); note the broad band of cryptocyst bounding the septular pores, and that the remaining parts of the distolateral vertical walls and orifice are entirely gymnocystal. C. Oral region of an ovicellate zooid of Atlantisina atlantis gen. et sp. nov. (paratype MNHN-IB-2014-49), showing the contact between the cryptocystidean frontal shield and the gymnocystal distal part of the zooecium; note that the frontal shield is superpositioned on the condyles (white arrow) and meets the distolateral vertical walls in a sinusoidal suture (black arrow). D. Initial stages of zooid formation with the lateral walls being partly broken, showing the large basal pore chambers in Atlantisina atlantis gen. et sp. nov. (paratype OLL 2016/123). E. Slightly oblique view of the ancestrula of Atlantisina tricornis gen. et sp. nov. (paratype MNHN-IB-2014-64); note the simple tatiform morphology, the absence of a cryptocyst, and the slightly restricted oral region (top). Scale bars: A–B, D = 100 µm; C, E = 50 µm.

Fig. 7. Atlantisina lionensis gen. et sp. nov., Lion Smt, paratype (MNHN-IB-2014-67). A. Colony overview. B. Orifice and slightly damaged ooecium. C. Ovicellate zooids at the colony growth margin. D. Close-up of the suboral crest. Scale bars: A = 500 µm; B, D = 50 µm; C = 100 µm.

Fig. 8. Atlantisina lionensis gen. et sp. nov. Intraspecific variability in the morphology of the suboral crest. Scale bar: 200 µm.