Atlantisina seinensis, 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 : 16-18

Atlantisina seinensis gen. et sp. nov.

urn:lsid:zoobank.org:act:E78F78F3-3E20-4F34-98E9-20441E929E45

Fig. 5 A–E, Table 5

Diagnosis

Frontal shield densely covered by relatively large, flattened nodules; lateral walls well developed, septular pores large, round to elongated oval, surrounded by a broad area of cryptocystal calcification; orifice margin with six oral spines; a single, large, pointed mucro with a broad base along the proximal orifice margin is positioned suborally. Ooecium longer than wide; ectooecium covering approximately the lower half of ooecium; exposed endooecium oval, convex, surface densely covered by numerous deep pits bounded by thickened ridges.

Etymology

Named after its type locality, Seine Smt.

Material examined

Holotype

SEINE SMT: 1 coated colony on biogenic concretion, Stn 42 ( MNHN-IB-2014-57 ).

Paratypes

SEINE SMT: 1 colony on small rock, Stn 41 (MNHN-IB- 2014-58); 3 small colonies (2 ovicellate, 1 immature) on small rock, Stn 42 (MNHN-IB- 2014-59); 1 colony on limestone, Stn 41 ( OLL 2016/144).

Description

Colony encrusting, unilaminar, forming small patches and/or bi- to triserial ribbons ( Fig. 5A ). Zooecia oval to polygonal, with tapering proximal end(s) wedged in between proximal zooecia, separated by deep grooves ( Fig. 5A ). Frontal shield convex, surface densely covered by relatively large, round to polygonal, flattened nodules ( Fig. 5 B–C), imperforate except for a few very small marginal pores, invisible in frontal view or in older zooecia; suboral frontal shield steeply raised to form a massive mucro with a pointed tip ( Fig. 5 B–C), lateral and distal part made of gymnocystal calcification, proximal face a continuation of nodular cryptocystal-type calcification of frontal shield, broad base of mucro framing proximal orifice margin and levelling towards proximal pair of spines; lateral walls well developed, septular pores relatively large, round to transversely oval, each pore surrounded by a broad cryptocystal area with an irregular surface ( Fig. 5B , D–E).

Orifice suborbicular to oval, slightly longer than wide, broadest at about mid-distance, proximal orifice margin slightly concave, poster comprising about one-third of entire orifice length, delimited from anter by a pair of very short and thick, blunt condyles directing proximomedially ( Fig. 5C ); lateral and distolateral margins with six closely-spaced spines with thick bases, arranged in two groups of three with a distinct distal gap ( Fig. 5 B–C); all six spines present in ovicellate zooids with distal pair a little thinner and resting firmly against proximolateral sides of ooecial peristome ( Fig. 5D ).

Ovicell hyperstomial, ooecium barely resting on frontal shield of distal zooid or free at colony margin, globular, distinctly longer than wide and with a short tubular peristome opening at distal orifice margin, ooecial aperture suborbicular, acleithral; a broad band of smooth ectooecial cover encompassing slightly more than the lower half of ooecium; endooecial surface densely covered by numerous, irregularly shaped, deep pits bounded by thick ridges, giving false appearance of a pseudoporous endooecium ( Fig. 5 D–E).

An ancestrula was not observed.

Remarks

Atlantisina seinensis gen. et sp. nov. is easily distinguished from all other species of Atlantisina gen. nov. owing to its single tall, triangular suboral mucro. Concerning frontal shield morphology, this species takes an intermediate position: whereas A. atlantis gen. et sp. nov., A. meteor gen. et sp. nov. and A. inarmata gen. et sp. nov. have the same type of nodular frontal calcification but lack a suboral mucro, all remaining Atlantisina gen. nov. species (see below) have complex mucrones but frontal shields with a honeycomb structure. The densely and deeply pitted endooecium in A. seinensis gen. et sp. nov. is, again, shared with A. inarmata gen. et sp. nov. from the Canary Islands.

Ecology

As in the other Atlantisina gen. nov. species, colonies of A. seinensis gen. et sp. nov. are small, combining spot- and runner-type characters (cf. Bishop 1989), and forming small patches with bi- to triserial ribbons. The colonies were found encrusting rocks at depths of 235– 260 m.

Distribution

This species is known only from Seine Smt.

Figures

Fig. 5. Atlantisina seinensis gen. et sp. nov., Seine Smt, holotype (MNHN-IB-2014-57). A. Autozooids and ovicellate zooids. B. Lateral view showing the vertical dimensions of the suboral umbones. C. Orifice. D. Ooecium. E. Early ontogenetic zooid with a fully formed ooecium. Scale bars: A–B = 200 µm; C–D = 50 µm; E = 100 µm.