Rhynchozoon revelatus, HAYWARD & McKINNEY, 2002

HAYWARD, PETER J. & McKINNEY, FRANK K., 2002, Northern Adriatic Bryozoa From The Vicinity Of Rovinj, Croatia, Bulletin of the American Museum of Natural History 2002 (270), pp. 1-139 : 96-98

Rhynchozoon revelatus , new species Figure 44A–D

Rhynchozoon species 2 : Hayward, 1974: 389. Zabala, 1986: 528. Zabala and Maluquer, 1988: 149.

DIAGNOSIS: Primary orifice wide, Dshaped, with widely spaced, fine denticles along distal rim; oral spines lacking; median suboral avicularium with distally­facing rostrum acute to frontal plane, accompanied by blunt uncinate process; dimorphic suboral avicularium.

HOLOTYPE: AMNH 1005.

PARATYPES: AMNH 1006, 1007, 1056; CMRR 2266–2269.

ETYMOLOGY: The species name is from the Latin revelatus (unveil).

DESCRIPTION: Colonies cream­colored, encrusting, multilaminar, developing domed, mamillate nodules, with mammillae forming incipient erect branches. Autozooids with thick, vitreous frontal shield, bordered by a single series of large marginal pores. Primary orifice wider than long, D­shaped; distal rim with fine, widely spaced denticles, proximal rim straight, small rounded condyles just visible in proximolateral corners. No oral spines. Peristome a thick, low rim, not obscuring orifice; median suboral avicularium present on most autozooids, with distally hooked, triangular rostrum orientated acute to frontal plane and facing distolaterally. Adjacent to proximal part of avicularium, peristome rim is shallowly notched, and a short, blunt uncinate process projects from base of avicularium cystid; apical part of cystid variably developed as a stout umbo. Suboral avicularium dimorphic, in most autozooids rostrum length less than width of orifice; massive type with broadly triangular, distally hooked rostrum,>0.3 mm long. In smaller avicularia, crossbar complete and thickened, but larger type lacks a columella; there is no palate. No frontal adventitious avicularia. Ovicell elongate oval, flat frontally, with a broadly arched aperture; projecting vertically above peristome rim; smooth surfaced, frontal ectooecium almost entirely membranous. In large colonies, greater than 2 cm high and wide, basal surfaces largely unattached to the substratum.

Ancestrula 0.25 mm long with transversely oval opesia occupying half frontal surface, bordered by undetermined number of spines. Two to four spines present in first three to four astogenetic generations only.

Tentacles clear, 12–13 in zooids closest to ancestrula, 14 –15 in subsequent zooids; lophophores bell­shaped, radially symmetrical midway between chimneys, grading to strongly obliquely truncate, campylonemidan, in some instances scalloped adjacent to chimneys.

OCCURRENCE: Diverse shell substrata; common on the thecate ascidian Microcosmus .

DISTRIBUTION: Originally recorded from Chios, Aegean Sea, this species has remained undescribed although it has been reported from several other localities in the Mediterranean. It was extremely common in the Rovinj region.

MEASUREMENTS (SKELETAL): AL(large) 384 ± 7 2 µm, 222–474 (3, 12), AW(large) 257 ± 74, 136–386 (3, 10), AL(small) 146 ± 12, 132–167 (1, 10), AW(small) 102 ± 9, 92– 117 (1, 10), DO 472 ± 97, 334–691 (3, 30), OL 118 ± 7, 106–133 (3, 30), OW 162 ± 12, 140–187 (3, 30), OvL 190 ± 24, 148– 220 (3, 6), OvW 259 ± 34, 196–286 (3, 6), ZL 658 ± 83, 556–770 (1, 10), ZW 404 ± 19, 370–431 (1, 10). (POLYPIDE): IH 116 ± 59 µm, 40–300 (2, 24), LDMn 608 ± 70, 500–740 (2, 23), LDMx 692 ± 166, 500– 1140 (2, 30), MD 25 (1, 1), TLMn 592 ± 55, 420–680 (2, 25).

GENUS SCHIZOTHECA HINCKS, 1877

Schizotheca fissa (Hincks, 1856) Figure 44E–H

Figures

Fig. 44. A–D. Rhynchozoon revelatus. A. General aspect (holotype, AMNH 1005; 0.5 mm). B. Autozooids and (bottom right) maternal zooid with ovicell (holotype, AMNH 1005; 0.1 mm). C. Autozooidal orifice (holotype, AMNH 1005; 0.05 mm). D. Ancestrula (center) and early autozooids (paratype, AMNH 1056). E–H. Schizotheca fissa. E. Entire, untreated colony (AMNH 942; 0.5 mm). F. Maternal zooid with normal ovicell (AMNH 1009; 0.1 mm). G. Oblique view from distal end of maternal zooid with ovicell bearing distal adventitious avicularium (AMNH 1010; 0.1 mm). H. Ontogenetically young, untreated autozooids (AMNH 942; 0.1 mm).