Stephanotheca bahloo, Cumming & Sebastian, 2018

Cumming, Robyn L. & Sebastian, Pascal, 2018, New encrusting species of Lanceoporidae (Bryozoa, Cheilostomata) from the southern Great Barrier Reef, Australia, Zootaxa 4500 (1), pp. 104-114 : 108-110

Stephanotheca bahloo n. sp.

( Fig. 2 , Table 2)

Material examined. Holotype: MTQ G101186, Sykes Reef, Capricorn Bunker Group, southern GBR, 23° 25' 26.112" S, 152° 1' 47.64" E, 14 November 2010, coll. CReefs Australia Project.

Etymology. The epithet is for Bahloo, the moon god of Australian aboriginal mythology, referring to the shape of the crescentic pseudoporous area in the ooecium.

Description. Colony encrusting, unilaminar. Autozooids rectangular to irregularly polygonal (c. 0.4 x 0.3 mm; Table 2); frontal shield flattened to slightly convex, pseudopores rounded, relatively sparse and widely separated (average 29 per zooid), diameter c. 0.018 mm, more sparse towards zooid borders; interzooidal boundaries marked by thin suture lines and areolae.

Primary orifice strongly oval, wider than long (c. 0.13 x 0.09 mm), poster with a rounded V-shaped sinus; condyles rounded, serrate. Adventitious avicularia small, rounded subtriangular (c. 0.08 long x 0.05 wide mm), suboral, medial, one per zooid, directed proximally, distance to orifice less than one avicularium length; cystid not raised above frontal shield; widest proximally, proximal opesia and rostral foramen oval to semicircular, crossbar central, complete. Vicarious avicularia absent.

Ovicell hyperstomial (prominent); ooecium as wide as long (c. 0.4 x 0.4 mm), with a central perforated area, semicircular distally and with two concave arches proximally, pseudopores irregular in shape and variable in size, bordered distally by an arch of nodules, cormidial, as indicated by Y-shaped suture lines; pronounced orifice dimorphism, ovicellate orifice wider than autozooid orifice (c. 0.19 vs. 0.13 mm), sinus very shallow, condyles smooth.

Occasional dimorphic zooids ( Fig. 2A , centre left) with larger orifice, wider than long (c. 0.18 x 0.10 mm) and a shallow sinus ( Fig. 2E ).

Remarks. Stephanotheca bahloo n. sp. is distinguished from all other known Stephanotheca species by the strongly oval primary orifice, the most pronounced orifice dimorphism, and the distinctive crescentic pseudoporous area of the ooecium, its shape resembling the popular depiction of “the man in the moon”. The other known species have moderate [ Stephanotheca romajoyae Cumming, 2015 , Stephanotheca watersi Reverter-Gil, Souto & Fernández-Pulpeiro, 2012 , Stephanotheca ochracea ( Hincks, 1862) and Stephanotheca kutyeri n. sp.] or minimal orifice dimorphism. Other Stephanotheca species have a relatively round primary orifice. Those of Stephanotheca victoriensis Reverter-Gil, Souto & Fernández-Pulpeiro, 2012 , Stephanotheca fenestricella Dick & Grischenko, 2017 and Stephanotheca kutyeri n. sp., are wider than long, but not as strongly so as those of S. bahloo n. sp. No other known species shares the crescentic shaped pseudoporous area of the ooecium.

The small, rounded subtriangular avicularium of Stephanotheca bahloo n. sp. is also distinctive. The avicularia of most other Stephanotheca species are either oval or triangular, and Stephanotheca romajoyae , from the nearby Gulf of Carpentaria, is the only other known species with subtriangular avicularia. But its avicularia are longer and narrower than those of S. bahloo n. sp., and S. romajoyae also differs in having large dimorphic avicularia and different ooecium morphology.

Stephanotheca bahloo n. sp. is quite distinct from the other Australian Stephanotheca species. Stephanotheca victoriensis is known only from Western Port Bay, Victoria, has a rounder orifice, a larger, wider, oval avicularium, and a single arched row of pseudopores on the ooecium. Stephanotheca ambita ( Waters, 1889) is known only from Port Jackson in Sydney Harbour, New South Wales, has a rounder orifice, smooth condyles, a small, oval suboral avicularium wider than long, and a round and much larger pseudoporous region of the ooecium. Stephanotheca ipsum Cumming, 2015 , from the Gulf of Carpentaria, has a distinctively round orifice and avicularia, and a fully pseudoporous ooecium with a slight ridge around the edge. It’s placement in Stephanotheca remains provisional (see Cumming 2015).

The orifice of the dimorphic zooid ( Fig. 2A ), resembles those of maternal zooids in size, shape (wider than long, shallow sinus) and condyles (smooth).

Distribution. The single known specimen of Stephanotheca bahloo n. sp. is from Sykes Reef, near Heron Island, Capricorn Bunker Group, southern GBR, depth unknown.

SD, standard deviation

Figures

FIGURE 2. Stephanotheca bahloo n. sp. Holotype (MTQ G101186). A. Autozooids, ovicellate zooid and dimorphic zooid (centre left). B. Primary orifice and avicularium. C. Ovicellate orifice. D. Ovicellate zooids. E. Orifice of dimorphic zooid shown in A. F. Primary orifice condyle.