Thornelya fuscina Tilbrook, Hayward & Gordon, 2001

Jain, Sudhanshi S., Gordon, Dennis P., Huang, Danwei, Kuklinski, Piotr & Liow, Lee Hsiang, 2022, Targeted collections reveal new species and records of Bryozoa and the discovery of Pterobranchia in Singapore, Raffles Bulletin of Zoology 70, pp. 257-274 : 262

Thornelya fuscina Tilbrook, Hayward & Gordon, 2001

( Fig. 7A )

Our material is not perfectly preserved, with many orifices and avicularia damaged, but enough characters are available to determine the species. Key features include the orifice (which is not parallel-sided as in Thornelya ceylonica ( Thornely, 1905) and has a narrower sinus), and the small avicularia, which are fewer than in T. ceylonica and can sometimes be arranged in a set of three, comprising a pair flanking an orifice and another, distal to the orifice, on the succeeding zooid. This arrangement is the origin of the name fuscina (three-pronged fork). There are three oral spines. The occasional large avicularia illustrated by Tilbrook (2006) in T. fuscina were not seen in our material. Autozooids measure 407‒586 μm long (mean 501 μm) and 294‒443 μm wide (mean 358 μm), compared to that of colonies from Efate, Vanuatu (type locality), with a mean zooid length of 560 μm and width of 460 μm ( Tilbrook et al., 2001); zooids from the Solomon Islands were cited as averaging 570 μm long and 480 μm wide ( Tilbrook, 2006). Zooids in the Singapore material overlap with published ranges for length but are non-overlapping for width. The only other validated Thornelya species from the tropical western Pacific is T. perarmata Harmer, 1957 ; it differs from T. fuscina in having narrow parallel-sided orifices, six oral spines, and numerous small adventitious avicularia distributed around the margins of the zooid as well as near the orifice. Hippomenella mila Scholz, 1991 from the Philippines may belong to Thornelya (see Tilbrook, 2006: 342; Bock, 2022), but it has orifices that are as wide as long and 5‒8 oral spines.

Figures

Fig. 7. A, Thornelya fuscina Tilbrook, Hayward & Gordon, 2001; white arrows indicate three unbroken latero-oral avicularia; B, Scorpiodinipora costulata (Canu & Bassler, 1929); C‒G, Rhabdopleura sp.; C, D, lateral view of erect tubes with annular fusellar rings; E, part of creeping basal tube in vicinity of three broken bases of erect tubes; here the fusellar sutures are parallel to oblique; F, G, parts of creeping basal tube in which the fusellar sutures (arrowheads) are arranged obliquely. Scale bars = 0.5 mm (A, B); 0.1 mm (C, D); 0.2 mm (E‒G).