Adeonellopsis gracilis, 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 : 323-325

Adeonellopsis gracilis n. sp.

( Figs 3I , 16 , 17C ; Tables 1, 2)

Etymology. Latin gracilis , slender, alluding to the thin colony branches.

Material examined. Holotype: NIWA 92745 , Stn KAH1206 /4, 40.0140° S, 174.1600°E, South Taranaki Bight ,

64 m. Paratypes: NIWA 144899 , 146097 , 146099 , Stn TQI1201/25, 40.0013° S, 174.0112° E, South Taranaki Bight , 82 m. Other : NIWA 146153 , Stn W 74 .

Diagnosis. Branches slender, mostly 1 mm wide. Autozooids averaging 442 μm long, 222 μm wide. Spiramen longitudinally elongate and subtriangular, mostly with 6 pores. Small suboral avicularia paired, transverse, their acute tips touching. Smaller adventitious avicularia often occurring elsewhere on zooid. No large avicularia or interzooidal avicularia on branch margins. Putative gonozooids with proportionally narrower and wider orifices and larger spiramina with 10 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; 5–6 longitudinal series across width of branch. Neanic zooids variably elongate-subhexagonal. Interzooidal boundaries indicated by thin lines of calcification in interzooidal furrows, which are bordered by 9–14 small areolar pores (mostly 10–12) in a series around the entire zooidal margin. Autozooids averaging 442 μm long, 222 μm wide in about five series across branch width ( Fig. 16A ).

Autozooidal peristomial orifice more or less transversely oval to roundly D-shaped, the unbroken distal margin sometimes raised forward and cowl-like; proximal margin straight or weakly concave. Discrete round spiramen lacking; instead, 4–11 spiraminal pores arranged in median longitudinal row, frequently subtriangular ( Fig. 16B, E ); distribution of pores in proximal direction variable, generally 2-2-1, 1-2-2-1, 2-1-1-1- 1 in neanic zooids; average length 114 μm, width 53 μm. Spiraminal spokes 6–10, varying in length, simple or bifurcate, some touching or overlapping; spiraminal area increasingly sunken as zooids age with some pores immersed in and concealed by calcification.

Suboral avicularia ( Fig. 16 B–D) paired (very rarely single), their cystids merged and rostra directed transversely or slightly obliquely toward each other, their tips sometimes touching. In ephebic zooids, orifice, suboral avicularia and spiramina in common furrow. No large avicularia or interzooidal avicularia on branch margins.

Putative gonozooids ( Fig. 17C ) with proportionally narrower and wider orifices (mean width 103 μm) and larger spiramina with 10 pores.

Ancestrula and early astogeny not seen.

Remarks. Adeonellopsis gracilis n. sp. is wholly endemic to New Zealand. Its branches are as slender as those of A. minor n. sp., but it has the smallest zooids, orifices and suboral avicularia of any of the species described herein. Apart from its diminutive dimensions, the most distinctive zooidal attributes are the elongate-triangular distribution of spiraminal pores and the consistently transverse orientation of the paired suboral avicularia.

An undescribed late Eocene Australian fossil [Brown’s Creek Clay, Aldingan (Priabonian), southwest Victoria], in the collection of P.E. Bock may be an early antecedent of A. gracilis n. sp. —it has slenderer branches with only three longitudinal autozooidal series across the branch width but a similar elongate spiramen.

Distribution. New Zealand: Greater Cook Strait, 32– 80 m. Endemic.

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 16. Adeonellopsis gracilis n. sp. (NIWA 146097): A. Bifurcating stem. B. Autozooids transitioning from neanic to ephebic. C. Ephebic autozooids with spiramen buried in secondary calcification, resulting in only a single outer opening. D. Close-up of peristomial orifice, transversely opposed suboral avicularia and transitioning spiramen. E. elongate-triangular spiramen of neanic autozooid (NIWA 146099). Scalebars: A, 1 mm; B, 200 μm; C, 300 μm; D, 100 μm; E, 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.