Sinonereis Wu & Sun, 1979

Víctor M. CONDE-VELA & Xuwen WU, 2019, Revision of Sinonereis Wu & Sun, 1979 (Annelida: Nereididae), Zoosystema 41 (9), pp. 151-161 : 154-155

Genus Sinonereis Wu & Sun, 1979

Sinonereis Wu & Sun, 1979: 95 .

TYPE SPECIES. — Sinonereis heteropoda Wu & Sun, 1979 , by original designation.

DISTRIBUTION. — The only species, Sinonereis heteropoda , is distributed along Eastern Asian coasts (Yellow Sea to eastern Japan). The genus has been signaled from the Atlantic Ocean but these records deserve confirmation.

DIAGNOSIS (emended, new features highlighted in boldface). — Prostomium with entire anterior margin. Four pairs of anterior cirri. Pharynx surface smooth. Upper notopodial ligule present from chaetiger 4 in atokes and epitokes. Notopodial prechaetal lobe present throughout body. In males, chaetigers 5 to 7 with napiform dorsal cirri (i.e., cirrophores globose or ovoid, cirrostyles cirriform); parapodia of natatory region with four lamellar processes (dorsal lamella, ventral lamella, upper and lower lamellae of ventral cirri); females without heteronereid transformation. Notochaetae homogomph spinigers; neurochaetae homogomph spinigers and heterogomph falcigers in supra-acicular fascicles, heterogomph spinigers and falcigers in sub-acicular fascicles.

REMARKS

The original diagnosis by Wu & Sun (1979) focused in the presence of dorsal cirri with ‘inflated’ cirrophores in anterior chaetigers. Relevant features included in the new diagnosis are the presence of notopodial prechaetal lobes throughout the body, the presence of dorsal lobes in natatory chaetigers, the occurrence of notopodial dorsal ligules from chaetiger 4 in both atokes and epitokes (instead of 3 as usual in most nereidids), and the lack of heteronereid transformation in females. Other key features are the lack of both upper and lower lamellae (usually upper or both lamellae are present) and crenulations in dorsal cirri of natatory chaetigers.

Wu et al. (1985) placed Sinonereis into the subfamily Nereidinae based on the presence of biramous parapodia, a small number of chaetae in the first chaetigers, and single ventral cirrus in all chaetigers ( Wu et al. 1985: 44). Later, Sun & Yang (2004) placed Sinonereis in the subfamily Gymnonereidinae sensu Fitzhugh (1987) because of the lack of paragnaths in pharynx, and the presence of biramous parapodia.

In the phylogenetic analysis by Santos et al. (2005), Sinonereis has an uncertain subfamily condition, a similar condition for several other genera. In their cladograms, Sinonereis appeared in a clade together with Leptonereis Kinberg, 1865 , Tylonereis Fauvel, 1911 and Tylorrhynchus Grube, 1866 ( Santos et al. 2005: figs 7, 8). This clade was supported by the character of enlarged notopodial dorsal ligules (in posterior chaetigers) ( Santos et al. 2005), which match with Leptonereis , Tylonereis , and Tylorrhynchus , but not with Sinonereis . Sinonereis resembles Tylonereis and Ty - lorrhynchus by having neuropodial falcigers but separated from them by having basally expanded dorsal cirri, and unilobated neuropodial postchaetal lobes ( Santos et al. 2005); additional differences with these genera are the presence of pharyngeal papillae and compound spinigers only in Tylonereis , and lack of both notopodial dorsal ligules and neuropodial ventral ligules in Tylorrhynchus , whereas Sinonereis species have no papillae in pharynx, have both compound falcigers and spinigers, and both notopodial dorsal ligules and neuropodial ventral ligules.