Eusyllis Malmgren 1867

Genus Eusyllis Malmgren, 1867

Type species: Eusyllis blomstrandi Malmgren, 1867

Diagnosis. Medium to small sized eusyllines. Prostomium with 2 pairs of eyes, additional 1 pair of anterior eyespots occasionally present, and 3 antennae. Peristomium with 2 pairs of peristomial cirri. Antennae, peristomial and dorsal cirri throughout usually smooth, sometimes wrinkled to pseudoarticulated. Ventral cirri usually ovate to digitiform, ventral cirri of chaetiger 1 laminated, flattened, in some species. Compound chaetae throughout as heterogomph falcigers only, sometimes with elongated blades; dorsal and ventral simple chaetae only present on posterior body parapodia. Pharynx straight, armed with conical dorsomedial tooth and usually incomplete trepan, with denticles in ventral half only; trepan complete in larger specimens of some species.

Remarks. Members of this genus often have fragile bodies, breaking apart at intersegmental grooves, and antennae and cirri easily falling off. So, preserved material usually consists of numerous fragments of each specimen.

Two of the species treated in the present paper, Eusyllis liniata comb. nov. and E. nonatoi sp. nov., present inverted dorso-ventral gradation in the length of falciger blades (i.e., blades of dorsalmost falcigers are shorter than those of ventralmost ones) comparing to most syllids, although such condition in not always mentioned in species descriptions. However, a similar pattern has been observed for many species of Odontosyllis Claparède, 1863 (see Fukuda et al. 2013), which suggests that this should be better investigated in other taxa.

The genus currently consists of 10 species, including both new species described herein (cf. Brusa et al. 2013).