Hippomenella, Canu and Bassler, 1917

Arakawa, Shinji, 2024, Descriptions of Three Cheilostomatid Bryozoan Species from the Continental Shelf off Boso Peninsula, Japan, Species Diversity 29 (1), pp. 99-110 : 104-105

Hippomenella (?) coronula ( Ortmann, 1890) ( Fig. 4C–E )

Diporula coronula Ortmann, 1890: 39 , pl. 3, fig. 7. Hippomenella (?) coronula : Arakawa 1999: 79, pl. 9, fig. G. Hippomenella coronula : Hirose 2010: 109, pl. 185, figs A–D;

Arakawa 2020b: 55.

Material examined. NMNS PA 20506 (fragment of colony A, and single zooids, B, C), Station 1748, R / V Hakurei-Maru cruise GH-80-2.

Measurements (in mm). NMNS PA 20506. Autozooids (6, 3): ZL, 0.85–1.18 (1.048 ± 0.129); ZW, 0.57–0.95 (0.809 ± 0.139); OrL, 0.24–0.31 (0.262 ± 0.023); OrW, 0.22– 0.25 (0.231 ± 0.015). Small frontal avicularia (8, 3): AvL, 0.11–0.13 (0.117± 0.008); AvW, 0.07–0.12 (0.086 ± 0.015)

Description. Colony encrusting. Zooids rectangular, or pentagonal to hexagonal, separated by furrows. Frontal shield imperforate in suboral area, with two to five rows of areolar pores. Orifice horseshoe-shaped, with broad poster separated from anter by proximomedially directed condyles. Oral spines five to seven. Small frontal avicularia generally two, sometimes absent ( Fig. 4E ); mandibular portion rounded or subtriangular, directed proximolaterally. One or two additional avicularia near distal corner of zooid, small, or large and elongate ( Fig. 4C, D ). Ovicell not found.

Distribution. Sagami Bay, depth 185 m ( Ortmann 1890); eastern Sagami Sea, depth 65–77 m and 132–172 m ( Hirose 2010); east of Boso Peninsula, depth 65 m (this study).

Remarks: My material comprises one colony fragment and two single zooids, but their zooidal characters correspond to those of the lectotype for H. coronula , studied by Hirose (2010). Hirose considered Ortmann’s species to be synonymous with H. spatulata Harmer, 1957 [= Lepralia tuberculara var. avicularis Livingstone, 1926 ; Hayward and Cook (1983) raised this taxon to species rank as H. avicularis ]. However, H. avicularis has a large avicularium with a markedly expanded tip ( Livingstone 1926; Harmer 1957; Powell 1967; Gordon and Hondt 1997); H. coronula , which shows gradual expansion of the avicularian tip, is a distinct species. For the same reason, the species from South Africa ( Hayward and Cook 1983) and from Korea ( Rho and Seo 1986) need to be restudied. I infer the Korean species as H. coronula , but the suboral imperforate area is narrower than in Japanese materials.

This species included in the species group of H. vellicata having proximally directed frontal avicularia and an ooecium with radially arranged pseudopores. These features do not coincide with the diagnosis of Hippomenella amended by Berning (2013).

Figures

Fig. 4. Cribellopora connata (Ortmann, 1890) (A, B) and Hippomenella (?) coronula (Ortmann, 1890) (C–E). A, Ovicell and orifice, NMNS PA 20504; B, oblique view of zooid; arrows, three lateral communication pores, NMNS PA 20503B; C, single zooid with large avicularium, NMNS PA 20506B; D, single zooid, with relatively broad median imperforate area, NMNS PA 20506C; E, largest specimen, NMNS PA 20506A.Scale bars: A, B, 100µm; C–E, 200µm.