Arcotheres cyclinus (Shen, 1932)

Arcotheres cyclinus (Shen, 1932) View in CoL

Pinnotheres cyclinus View in CoL — Morton and Morton 1983: 202, fig. 9.9(7A). Pinnotheres obscurus View in CoL — Pregenzer and Morton 1990: 653 [part], fig.

3A, B.

Taxonomy: Shen (1932b), Sakai (1939), Ng et al. (2017b).

Type: Syntypes ññ in IOCAS.

Type locality: Xingcun (as Hsingtsun), Shandong, China.

Distribution: East Asia: coasts of China, Taiwan, Korea and Japan.

Habitat: Intertidal to subtidal; commensal with or parasite of bivalves, including Cyclina sinensis (Gmelin, 1791) , Meretrix meretrix ( Linnaeus, 1758) , Barbatia virescens (Reeve, 1844) , Geloina erosa (Solander, 1786) , on substrates of sand and mud, or attached to rocks ( Shen 1932b; Sakai 1939; Morton and Morton 1983).

Remarks: Pinnotheres cyclinus Shen, 1932 (b) was placed under Arcotheres Manning, 1993 by Ng et al. (2017b), a decision we follow. We also consider material reported as P. obscurus in Pregenzer and Morton (1990) included P. cyclinus . See Remarks under P. obscurus below.

Arcotheres sinensis (Shen, 1932) #

Pinnotheres sinensis View in CoL — Morton and Morton 1983: 202, fig. 11.18(10); Morton 1988: 82, pl. 25; Pregenzer and Morton 1990: 657.

Taxonomy: Shen (1932b: as Pinnotheres View in CoL ), Sakai (1939: as Pinnotheres View in CoL ), Takeda and Konishi (1988: as Pinnotheres View in CoL ).

Type: Holotype ñ ZMFMIB No. 8756: status unknown.

Type locality: Qingdao (as Tsingtao), Shangdong, China.

Distribution: East Asia: coasts of China, Taiwan, Korea and Japan.

Habitat: Intertidal to subtidal; commensal with or parasite of bivalves, including Barbatia virescens (Reeve, 1844) , Chlamys farreri (Jones & Preston, 1904) , Megallana gigas (Thunberg, 1793) , Meretrix lusoria (Röding, 1798) , Modiolus auriculatus (Krauss, 1848) , Mytilis edulis Linnaeus, 1758 , M. unguiculatus Valenciennes, 1858 , Perna viridis ( Linnaeus, 1758) , Ruditapes philippinarum (Adams & Reeve, 1850) and Venerupis aspera (Quoy & Gaimard, 1835) , on substrates of sand and mud, or attached to rock surfaces ( Sakai 1976; Pregenzer and Morton 1990).

Remarks: Reports of this species from India by Sethuramalingam and Khan (1991), Ravichandran and Kannupandi (2007) and Kannappan et al. (2012) are doubtful and probably belong to another species. As discussed by Ahyong and Ng (2007) and Ng and Ahyong (2022), A. sinensis is morphologically similar to A. alcocki ( Rathbun, 1909) and the taxonomy of the two species (as well as allied taxa) will need to be reappraised. The reported variety of hosts used by A. sinensis is also suspicious — some are probably incorrect and there may be more taxa mixed under what has been identified as “ A. sinensis ”.