Tessaradoma japonicum, Arakawa, 2024

Arakawa, Shinji, 2024, Descriptions of Three Cheilostomatid Bryozoan Species from the Continental Shelf off Boso Peninsula, Japan, Species Diversity 29 (1), pp. 99-110 : 101-102

publication ID	https://doi.org/ 10.12782/specdiv.29.99
publication LSID	lsid:zoobank.org:pub:EA59EB18-8759-401A-96E0-62C2E9896A94
persistent identifier	https://treatment.plazi.org/id/7CC71F35-AD2A-44F9-9C68-B5B71DB25B29
taxon LSID	lsid:zoobank.org:act:7CC71F35-AD2A-44F9-9C68-B5B71DB25B29
treatment provided by	Felipe
scientific name	Tessaradoma japonicum
status	sp. nov.

Treatment

Tessaradoma japonicum sp. nov.

( Figs 1 View Fig , 2 View Fig , 3A View Fig )

Tessaradoma View in CoL (?) sp.: Arakawa 1999: 65, pl. 5, fig. D. Semihaswellia View in CoL (?) sp.: Arakawa 2020b: 54.

Material examined. Holotype: NMNS PA 20496 View Materials , Station 1709, R / V Hakurei-Maru cruise GH-80-2 . Paratypes: NMNS PA 20497, Station 1734, R / V Hakurei-Maru cruise GH-80-2; NMNS PA 20498–20500, same station as holotype.

Diagnosis. Colony erect, composed of two or three series of zooids facing one side of the branches. Frontal shield granular, striated near lateral margin, with areolar pores. Semicircular orifice immersed at the bottom of a projecting peristome. Avicularia lacking. Ovicell peristomial; ooecium imperforate.

Etymology. The specific name refers to the region of Japan.

Measurements (in mm). NMNS PA 20496–20499. Autozooids (23, 4): ZL, 1.25–1.96 (1.598 ± 0.175); ZW, 0.68– 0.93 (0.806± 0.064); SOrL, 0.15–0.26 (0.214 ± 0.033); SOrW, 0.20–0.26 (0.230 ± 0.015). Ovicells (5, 2): OvL, 0.44–0.58 (0.513 ± 0.069); OvW, 0.48–0.54 (0.522 ± 0.033).

Description. Colony erect, bifurcate; branches about 1.0– 1.4 mm in diameter. Zooids arranged in two or three longitudinal series, facing one side of the branches, hexagonal or pentagonal, separated by furrows ( Figs 1A View Fig , 2A View Fig ). Frontal shield inflated, granular, sometimes longitudinally striated near lateral margins, with a row of areolar pores; umbonuloid component relatively conspicuous on inner side ( Fig. 3A View Fig ). Spiramen situated in center of zooid, bordered by short, crown-like ring of calcification ( Fig. 2E View Fig ). Primary orifice ( Fig. 2C, D View Fig ) semicircular, with small lateral condyles, immersed at the bottom of a peristome. Peristome tall, raised, granular; secondary orifice circular, or horseshoe-shaped with straight proximal border. Avicularia lacking. Ovicell globular or bag-shaped, covering distal or distolateral side of peristome; ooecium granular ( Fig. 1B–D View Fig ).

Distribution. East of Boso Peninsula, at depths of 144 and 155 m.

Remarks. This species resembles Semihaswellia umbrella Gordon and Hondt, 1997 from New Caledonia in the colony form and in zooids having an elevated raised peristome and salient spiramen. However, my material cannot be placed in Semihaswellia Canu and Bassler, 1917 because the frontal shield and ooecium are imperforate. Although the frontal shield is striated mainly near the lateral margins, my material appears to belong in Tessaradoma . Tessaradoma boreale shows conspicuous frontal striation, but younger zooids at the distal end of branches from Shetland are not striated ( Gordon 1993), and ovicellate zooids in a Floridian specimen are also only granulated ( Winston 2005).

Tessaradoma japonicum sp. nov. differs from other Tessaradoma species in colonies composed of zooids facing one side of the branches. In addition, the ovicell differs in structure from that in other species, except for T. boreale report- ed by Souto et al. (2016). The boundary between the ovicell and the next zooid is a deep furrow in British and Floridian examples of the genus ( Hayward and Ryland 1979, 1999; Winston 2005), whereas the ooecium in T. japonicum sp. nov. ( Fig. 1E View Fig ) and T. boreale from the Galicia Bank is continuous with the frontal wall of the next zooid. In T. japonicum sp. nov., the ovicell extends upward along the peristome ( Fig. 1C, D View Fig ), and occasionally overhangs the distal edge of peristome due to the secondary calcification (? regeneration) of the next zooid ( Fig. 2B View Fig ).

The taxon referred as “ Margaretta n. sp. ” by Hirose (2010: 118, pl. 203) from northeast off Hachijo-jima may also be placed in Tessaradoma . Although its frontal granulation is not striated, Hirose’s species is very similar to T. japonicum sp. nov. in the imperforate frontal shield, the projecting peristome, and the position of the spiramen. The colony is, however, composed of 6–7 series of zooids facing all around the branches as in T. boreale .

Harmer (1957) inferred a colony fragment in the Mitsukuri Collection of the Cambridge Museum (now in the Natural History Museum, UK; see Spencer Jones et al. 2011) as his new species Tessaradoma bipatens Harmer, 1957 from west Waigeo Island, Indonesia. This species, however, is now placed in Galeopsis Jullien, 1888 ( Bock 2016). The Mitsukuri’s Japanese collection also needs to be re-examined.