Opisthodonta Langerhans, 1879

Fukuda, Marcelo V., Nogueira, João M. M. & Martín, Guillermo San, 2015, Eusyllinae and “ Incertae sedis ” syllids (Annelida: Syllidae) from South America, with a new species from Brazil and a new combination for a Peruvian species, Zootaxa 3936 (4), pp. 507-537 : 525

Genus Opisthodonta Langerhans, 1879

Type species: Opisthodonta morena Langerhans, 1879

Diagnosis. Body of medium to large size. Prostomium with 2 pairs of eyes and 1 pair of anterior eyespots; 3 antennae; palps basally fused, usually broader than prostomium. Nuchal organs as 1 pair of ciliated grooves between prostomium and peristomium; peristomium with 2 pairs of cirri. Antennae, peristomial and dorsal cirri throughout smooth, long and slender; anterior ventral cirri foliaceous, fused to parapodial lobes on anteriormost chaetigers, remaining ventral cirri conical to digitiform. Compound chaetae as falcigers with bidentate blades, usually heavily spinulated; spiniger-like chaetae present in some species. Dorsal and ventral simple chaetae rarely present. Massive pharynx and proventricle, pharyngeal tooth away from anterior margin, usually near mid-length of pharynx; trepan absent. Reproduction by epigamy (cf. San Martín 2003).

Remarks. Despite being relatively large syllids, members of Opisthodonta have fragile bodies, easily breaking apart by handling. Depending on the collection methodology, complete specimens are rarely obtained, thus accurate descriptions of these taxa are frequently not possible. In some cases, such as in Opisthodonta russelli San Martín, López & Aguado, 2009, original descriptions were based only on fragments; thus, some data on posterior body characters are first reported herein.

This is the first occurrence of the genus for the Brazilian coast.