Adeonellopsis minor, Liow & Gordon, 2020

Liow, Lee Hsiang & Gordon, Dennis P., 2020, New species of Adeonellopsis (Bryozoa: Adeonidae) from southern Zealandia and the western Tasman Sea, Zootaxa 4895 (3), pp. 301-331 : 322

Adeonellopsis minor n. sp.

( Figs 3H , 15 , 17B ; Tables 1, 2)

Etymology. Latin minor , smaller, the comparative form of parvus, alluding to the small colony and branch sizes.

Material examined. Holotype: Australian Museum U. 5798, from NIWA Stn U 207, 34.1850° S, 151.4333° E, 198 m, New South Wales shelf, Tasman Sea . Paratypes: Australian Museum U. 5799, same data as holotype ; NIWA 146152 , same data as holotype .

Diagnosis. Branches slender, mostly 1 mm wide. Autozooids averaging 607 μm long, 270 μm wide. Autozooi-dal spiramen circular–oval with 3–4 pores. Small suboral avicularia mostly paired and directed distally. One other such avicularium at proximal end of zooid in ephebic zooids. Subvicarious avicularia on branch margins. Putative gonozooids slightly larger than autozooids, with larger orifices and spiramina, the latter with 6 pores.

Description. Mature intact colony not seen. Isolated branches slender, 0.8–1.1 mm wide, mostly 1 mm, more or less bifurcating in more than one plane, twiggy. Colour of dried colony pale creamy-brown.

Autozooids arranged in quincunx; 4–5 longitudinal series across width of branch. Neanic zooids roundly elongate-subhexagonal to elongate-rectangular. Interzooidal boundaries indicated by thin lines of calcification in interzooidal furrows, which are bordered by 13–17 small areolar pores in a series around the entire zooidal margin. Autozooids averaging 607 μm long, 270 μm wide in 4–5 series across the branch ( Fig. 15A ).

Autozooidal peristomial orifice suborbicular to more or less transversely and roundly D-shaped; the inner proximal marginal with sparse denticulation ( Fig. 15C ) or this lacking. Spiramen ( Fig. 15D ) circular–oval, averaging 79 μm long, 63 μm wide, with 3–4 spiraminal pores, each with mostly very short spokes that do not touch; becoming relatively quickly sunken.

Suboral avicularia ( Fig. 15B, G ) small, squat, mostly paired, generally off-centre if single and an adjacent areola pore (source of avicularium) in place of second suboral avicularium; rostrum mostly directed distally, sometimes transversely or obliquely, the tip closed (lacking channel). Common rostral-opesial foramen lacking denticulation of margin; cryptocyst smooth.

Subvicarious avicularia ( Fig. 15E, F ) on branch margins; like adventitious zooidal avicularia but rostral-opesial portion more elongate, the rostral tip closed, opesial cryptocyst smooth; articular pivot ridges short, thin, curved.

Putative gonozooids ( Figs 15B ; 17B ) slightly larger than autozooids, with larger orifices and spiramina, the latter with 6 pores.

Ancestrula and early astogeny not seen.

Remarks. Adeonellopsis minor n. sp. closely resembles Adeonellopsis gracilis n. sp. in its very slender branches but differs from it in having a larger zooid size and rounded spiramina. Adeonellopsis minor n. sp. also superficially closely resembles A. gemina n. sp., but most obviously differs from it in having thinner branches, larger autozooids and smaller dimensions for the subvicarious marginal avicularia. Adeonellopsis minor n. sp. differs from A. yarraensis in having the autozooidal spiramen close to the orifice, such that the orifice, suboral avicularia and spiramen can be partly immersed in a common furrow of secondary calcification in highly ephebic zooids.

Distribution. Australia: New South Wales shelf, 198 m.

Figures

FIGURE 3. A, B. Adeonellopsis macewindui n. sp.: A. Holotype, NIWA 146070; B. NIWA 146098. C. Adeonellopsis tasmanensis n. sp., composite of three fragments, all NIWA 144892. D. Adeonellopsis periculosa n. sp., holotype, NIWA 146071. E. Adeonellopsis wassi n. sp., composite of three fragments, all NIWA 144898. F, G. Adeonellopsis gemina n. sp.: F. holotype, NIWA 146095; G. Two specimens, NIWA 146073. H. Adeonellopsis minor n. sp., composite of four fragments, NIWA 146152. I. Adeonellopsis gracilis n. sp., composite of two fragments, holotype (larger specimen), NIWA 92745; smaller specimen (separated by thin gap), NIWA 146099. Specimens A–I at same scale; scalebar 5 cm.

FIGURE 15. Adeonellopsis minor n. sp. (NIWA 146152): A. Branching stem. B. Autozooids and, at right, a zooid with a larger orifice and spiramen (gonozooid?). C. Autozooidal peristomial orifice with sparse denticulation of inner rim. D. Autozooidal spiramen. E. Branch margin with subvicarious avicularia. F. Close-up of marginal avicularium. G. Close-up of orifice, suboral avicularia and sunken spiramen of autozooid at left in B. Scalebars: A, 1 mm; B, E, 300 μm; C, 40 μm; D, F, G, 50 μm.

FIGURE 17. Putative gonozooids (pgz). A. Adeonellopsis gemina n. sp. (NIWA 146086), with eight spiraminal pores. B. Adeonellopsis minor n. sp. (NIWA 14899), showing a broad orifice and six spiraminal pores. C. Adeonellopsis gracilis n. sp. (NIWA 92745), with broad orifice and spiramen of ten scattered pores. Scalebars: A–C, 200 μm.