Calyptotheca tilbrooki, Sebastian & Cumming, 2016

Sebastian, Pascal & Cumming, Robyn L., 2016, Three new species of Calyptotheca (Bryozoa: Lanceoporidae) from the Great Barrier Reef, tropical Australia, Zootaxa 4079 (4), pp. 467-479 : 472-475

Calyptotheca tilbrooki n. sp.

( Figs 3 , 4 , Table 2)

Material examined. Holotype: MTQ G26785, GBR lagoon, Innisfail region , 17°59.1' S, 146°47.5' E, 29 April 2004, 34 m, coll. Seabed Biodiversity Project.

Paratype: MTQ G26786, GBR lagoon, Shoalwater Bay region , 21°73.5' S, 149°.60.5' E, 4 October 2004, 16 m, coll. Seabed Biodiversity Project.

Etymology. Honorific for Dr Kevin J. Tilbrook, in recognition of his contribution to the bryozoan collections at MTQ and to the taxonomy of Bryozoa .

Description. Colony encrusting, multilaminar, forming thick upright multilamellar fronds ( Fig. 3A, B ), orange-red in ethanol; autozooids rectangular to irregularly polygonal (c. 0.5 x 0.5 mm; Table 2); frontal shield flattened to slightly convex with rounded pseudopores (average 23 per zooid), sparser or absent proximal to orifice, in zooid centre and towards zooid borders; interzooidal boundaries marked by thin raised lines of calcification with irregular marginal areolae.

Primary orifice wider than long (c. 0.10 x 0.12 mm); lunula extending laterally, continuous with condyles; sinus a shallow rounded arc; condyles large, not serrate; raised nodular thickening proximal to orifice.

Adventitious avicularia elongate-oval, some slightly wider distally (c 0.09 x 0.04 mm); marginal; most often in one or both proximal angles, sometimes on proximolateral margin; 0–3 per zooid, often absent; directed distally or distolaterally; proximal opesia semicircular, rostral foramen semielliptical, crossbar complete.

Vicarious avicularia elongate-oval (c. 0.6 x 0.1 mm), without frontal shield; opesia oval, rostral foramen triangular with concave distal sides, crossbar complete, with large columella directed distally.

Ooecium immersed, not raised above surrounding zooids, wider than long (c. 0.4 x 0.5 mm), sometimes crossed by sutural lines; pseudopores of both ooecium and ovicellate zooid frontal shield similar in size but in greater density (c. 73 vs 23 pseudopores per zooid) than autozooidal frontal shield, sometimes 2–3 pseudopores share same pit; pronounced orificial dimorphism, ovicellate orifice twice as wide (c. 0.24 vs 0.12 mm) and longer (c. 0.15 vs 0.10 mm) than autozooidal orifice; sinus wide and very shallow; condyles rounded, not serrate; suboral umbo present.

Remarks. Calyptotheca tilbrooki n. sp. is distinguished by its growth form of thick multilamellar mounds and fronds, long, oval vicarious avicularia, elongate-oval, marginal adventitious avicularia, pronounced orificial dimorphism, and distinctive high-density pseudopores in the ooecia and frontal shields of ovicellate zooids.

Seven Calyptotheca species have been described with vicarious avicularia, viz C. capitifera ( Canu & Bassler, 1929) , C. conica , C. inclusa , C. obscura Harmelin, López de la Cuadra & García-Gómez, 1989 , C. orbiculata Harmer, 1957 , C. reniformis Tilbrook, 2006 (unpubl. data in Cumming & Tilbrook 2014) and C. wulguru n. sp. All of these species except C. capitifera have the primitive form of vicarious avicularia that resemble autozooids with perforated frontal shields, but with greatly enlarged orifices. Those of C. capitifera therefore appear most similar to those of C. tilbrooki n. sp. (without a perforated frontal shield). Canu & Bassler (1929, pl. 32, fig. 5) described “the spatulate shape of interzooidal avicularia” of C. capitifera (not C. capitifera of Harmer 1957; see Cumming & Tilbrook 2014, p. 160). The vicarious avicularia of C. tilbrooki n. sp. are not spatulate but elongate-oval with acuminate rostral foramen, while those of C. capitifera , are semicircular and there are no adventitious avicularia.

The combination of shape and position of the adventitious avicularia of C. tilbrooki n. sp. is unique within the genus. The elongate oval shape does not conform to the C. wasinensis subgroup described above, despite having a similarly marginal position. The adventitious avicularia of C. thornelyae are most similar to those of C. tilbrooki n. sp., but pseudopore density of autozooidal and ooecial calcification is identical; there is no orificial dimorphism and vicarious avicularia are lacking ( Ryland & Hayward 1992, p. 260).

Calyptotheca tilbrooki n. sp. has the most pronounced known orificial dimorphism amongst Calyptotheca species, with the ovicellate orifice double the width of the autozooidal orifice.

A greater density of pseudopores on the ooecium was also described by Harmer (1957, p. 1020) in C. fossulata , which is distinguished from C. tilbrooki n. sp. by the lack of vicarious avicularia and having rounded marginal adventitious avicularia typical of the C. wasinensis subgroup.

Distribution. Calyptotheca tilbrooki n. sp. is known only from the GBR lagoon. One colony was collected from the Innisfail area at 34 m and one colony from the Shoalwater Bay region, North of Yeppoon at 16 m.

Figures

FIGURE 3. Calyptotheca tilbrooki n. sp.: A, holotype (MTQ G 26785), multilamellar frond; B, paratype (MTQ G 26786), a thick multilamellar encrusting colony with developing frond (top left).

FIGURE 4. Calyptotheca tilbrooki n. sp., holotype (MTQ G 26785): A, general view; B, adventitious avicularium; C, ovicellate orifice; D, ovicellate zooids, showing pronounced orificial dimorphism; E, autozooidal orifice; F, general view with autozooids and vicarious avicularia; G, vicarious avicularium; note the small adventitious avicularium at bottom.