Stephanotheca romajoyae, Cumming, Robyn L., 2015

Cumming, Robyn L., 2015, Two tropical species of Stephanotheca (Bryozoa, Cheilostomata, Lanceoporidae) from the Gulf of Carpentaria, Australia, Zootaxa 3948 (2), pp. 279-286 : 283-285

publication ID 10.11646/zootaxa.3948.2.8

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Stephanotheca romajoyae

sp. nov.

Stephanotheca romajoyae n. sp.

( Figure 2 View FIGURE 2 , Table 2 View TABLE 2 )

Material examined. Holotype: MTQ G26769, Bryomol Reef, 16°32.658' S, 139°53.567' E, 33 m. Paratypes: MTQ G26770, MTQ G26771, MTQ G26772, same data as for holotype; MTQ G26773, southeastern GoC, 16°40.914' S, 140°12.029' E, 33 m.

Etymology. Named for the author’s mother, Mrs Roma Joy Cumming.

Description. Colony encrusting, with frontal budding; autozooids irregularly polygonal, variable in size and shape (average 0.4 × 0.4 mm; Table 2 View TABLE 2 ), especially variable in width (s.d. 0.117); frontal shield flattened to slightly convex; pseudopores round, irregularly spaced (c. 0.012 mm diameter), most separated by more than the width of a pseudopore but some close together and sharing depressions or pits (average 47 per zooid), extending to zooid margins; interzooidal boundaries marked by sutural walls and regularly spaced, oval or round sutural pores that are larger than pseudopores in the frontal shield.

Primary orifice wider than long (c. 0.09 long × 0.10 wide mm), broadest centrally; anter rounded; lunula extends to lateral margins and appears continuous with condyles; sinus a shallow arc; condyles large, rounded, serrate; a raised nodular thickening proximal to orifice.

Adventitious avicularia dimorphic in size, shape and position; usually one per zooid, occasionally two; smaller type common (c. 0.09 long × 0.04 wide mm at crossbar); subtriangular; widest proximally; proximal opesia semicircular, rostral foramen trifoliate to rounded triangular; crossbar complete; usually suboral, medial, directed distolaterally; sometimes with slight asymmetry, curving towards orifice; occasionally directed proximolaterally or positioned in a distolateral corner; occasional second avicularium positioned more proximally with variable orientation; larger type uncommon, occupying most of frontal shield (c. 0.28 long × 0.07 wide mm at crossbar); elongate oval with parallel sides; proximal opesia oval, rostral foramen rounded subtriangular with concave sides; crossbar complete; usually proximal, medial, directed distolaterally, terminating in a distolateral angle; vicarious avicularia absent.

Ovicell hyperstomial (prominent), recumbent on frontal shield of distal zooid; ooecium longer than wide (c. 0.4 × 0.3 mm); flattened frontally; with numerous pseudopores of variable shape and size, larger than those of frontal shield; an arch of nodules surrounding the pseudopores, terminating laterally; walls almost vertical, imperforate (height c. 0.06 mm); orifice dimorphic, ovicellate orifice longer (c. 0.11 vs. 0.09 mm) and much wider (c. 0.14 vs. 0.10 mm; Table 2 View TABLE 2 ) than autozooidal orifice (1-tailed t-test: p<0.001).

Remarks. The variability in avicularium size, shape, position and orientation sets Stephanotheca romajoyae n. sp. apart from all other Stephanotheca species. The nine temperate species described by Reverter-Gil et al. 2012 all have a single, medial, proximally directed adventitious avicularium. While S. romajoyae n. sp. also has a medial avicularium on each zooid, these vary in orientation from distolateral to proximolateral, there are also occasional additional avicularia elsewhere on the zooid, and occasional large elongate-oval avicularia that occupy most of the frontal shield. Sometimes the two different avicularium types occur together on a single zooid ( Figure 2 View FIGURE 2 A). Stephanotheca ipsum n. sp. is the only other Stephanotheca species with more than one avicularium on some zooids, but they are a distinctly different shape and are not dimorphic. Stephanotheca ochracea ( Hincks, 1862) is the only other species with dimorphic adventitious avicularia, but they are a different shape and proximally directed.

The level of variability in the avicularia of Stephanotheca romajoyae n. sp. resembles that of Calyptotheca australis ( Haswell, 1880) in the dimorphism, the variable orientation and in sometimes being slightly asymmetrical and curved around the orifice (see Cumming & Tilbrook 2014). These two species also share similar small orifices of the same dimensions (c. 0.09 × 0.10 mm) and large, serrate condyles. The ooecia of the two species are clearly different (those of C. australis are fully pseudoporous), but colonies without ovicells are readily distinguished by the much shallower sinus in S. romajoyae , avicularium shape and colony form. The small avicularia of S. romajoyae are subtriangular and widest proximally, whereas those of C. australis are narrowly triangular proximally and usually widest midlength. The large avicularia of C. australis are also narrowly triangular proximally, whereas those of S. romajoyae are elongate oval with parallel sides. The growth form of C. australis is a network of unilaminar tubes, whereas S. romajoyae is an encrusting species.

Stephanotheca romajoyae n. sp. has the smallest orifice of the Stephanotheca species (0.09 × 0.10 mm), followed closely by S. ipsum n. sp. (0.10 × 0.10 mm). The southern Australian species S. ambita and S. victoriensis also have smaller orifices than the European species (0.11 × 0.11 mm, 0.11 × 0.13 mm respectively vs 0.12–0.15 × 0.13–0.15 mm).

Stephanotheca ambita shares with S. romajoyae n. sp. a wide shallow sinus, but it has smooth rather than serrate condyles and a single, small, oval suboral avicularium. Stephanotheca victoriensis has a larger, wider, distinctly oval orifice, and a single oval avicularium distant from the orifice and almost in the centre of the zooid.

Orificial dimorphism occurs in all Stephanotheca species except S. perforata (0.15 vs 0.15 mm; Reverter-Gil et al. 2012), but is most pronounced in S. romajoyae n. sp., with ovicellate orifices much wider than autozooidal orifices (0.14 vs. 0.10 mm). The ooecia of S. romajoyae differ from those of all known Stephanotheca species in being longer than wide. Ooecia of the Australian species differ in various ways from the typical crowned ooecium of the European species: those of S. ipsum n. sp. are ridged, those of S. victoriensis have a single row of pseudopores forming an arch and those of S. ambita have a relatively large perforated area and smaller, lower nodular rim of calcification. S. romajoyae ooecia are most similar to those of S. ambita , with a similarly wide perforated area.

Distribution. Stephanotheca romajoyae n. sp. is known only from the GoC, with four colonies collected from the same site at Bryomol Reef, east of Mornington Island at 33 m, and a fifth colony from southeastern GoC at 33 m.

TABLE 2. Measurements (mm) and counts for Stephanotheca romajoyae n. sp. holotype (MTQ G 26769).

  Mean Standard deviation Range N
Zooid length 0.373 0.042 0.299–0.470 20
Zooid width 0.363 0.117 0.243–0.796 20
Autozooid orifice length 0.087 0.005 0.075–0.094 17
Autozooid orifice width 0.103 0.005 0.096–0.112 17
Small adventitious avicularium length 0.092 0.011 0.080–0.114 20
Small adventitious avicularium width at crossbar 0.040 0.004 0.034–0.048 20
Large adventitious avicularium length 0.283 0.009 0.276–0.289 2
Large adventitious avicularium width at crossbar 0.074 0.005 0.071–0.078 2
Diameter of pseudopores in frontal shield 0.012 0.002 0.008–0.015 20
Number of pseudopores in frontal shield 47 10.75 35–70 20
Ooecium length 0.392 0.014 0.369–0.406 5
Ooecium width 0.302 0.027 0.276–0.332 4
Ooecium height 0.057 0.023 0.041–0.073 2
Ovicellate orifice length 0.107 0.012 0.099–0.116 2
Ovicellate orifice width 0.140 0.004 0.135–0.144 4
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