Arbopercula, Nikulina, 2010

Taylor, Paul D. & Tan, Shau-Hwai Aileen, 2015, Cheilostome Bryozoa from Penang and Langkawi, Malaysia, European Journal of Taxonomy 149, pp. 1-34 : 10-11

Arbopercula sp.

Fig. 5 A–C

Material

MALAYSIA: MSL BRY009, Pulau Betong, Penang, on oyster rafts.

Description

Colony encrusting, multiserial, unilamellar, thinly calcified. Ancestrula and early astogeny not observed. Autozooids subhexagonal, slender, two or more times longer than wide, 0.49–0.63 mm long by 0.19–0.28 mm wide; boundaries between zooids in adjacent rows marked by a narrow fissure, lacking between zooids in the same row;opesia occupying nearly all frontal surface, ovoidal; cryptocyst developed only proximally, extremely narrow, steeply sloping; gymnocyst narrow, broadening in proximolateral corners; two oral spines, erect, short, tapering distally, often with ends closed; circumopesial spines numbering 6–14, generally paired on either side of opesia, long, tapering distally, overarching frontal membrane, not overlapping or touching ( Fig. 5B ); proximal circumopesial spine located close to and resembling morphologically the oral spines ( Fig. 5C ).

Remarks

The genus Arbopercula – type species Electra bengalensis Stolizcka, 1869 – was proposed by Nikulina (2010) for species previously included in Electra , but which have spines on the operculum. These unmineralized structures have not been observed in the dried material from Penang, which has lost the opercula. Nevertheless, the Penang bryozoan does show a strong overall resemblance to the specimen figured by Gordon et al. (2007, fig. 1C) as the type species, particularly in the gymnocystal spinosity, and also to Arbopercula devinensis ( Robertson, 1921) , although differences in the distribution and number of spines, plus the extent of the proximal gymnocyst, preclude unequivocal identification as either of these two species.

Figures

Fig. 5. — A–C. Arbopercula sp. Pulau Betong, Penang, MSL BRY009. A. Group of zooids. B. Zooids showing spines. C. Distal end of a zooid with a pair of oral spines and the proximal circumopesial spine of the next distal zooid. — D–F. Sinoflustra amoyensis (Robertson, 1921). Batu Muang, Penang, MSL BRY010. D. Part of a colony. E. Detail of a group of zooids at the broken edge. F. Opesia and cryptocystal spinules. Scale bars: A, D = 500 μm; B, E = 200 μm; C, F = 100 μm.