Riseriopsis, Salazar-Vallejo & Zhadan & Rizzo, 2019

Salazar-Vallejo, Sergio I., Zhadan, Anna E. & Rizzo, Alexandra E., 2019, Revision of Fauveliopsidae Hartman, 1971 (Annelida, Sedentaria), Zootaxa 4637 (1), pp. 1-67 : 56-57

Riseriopsis new genus

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Type species: Riseriopsis santosae n. sp. Diagnosis. Fauveliopsids with body cylindrical, slightly swollen anteriorly, markedly swollen posteriorly. Anterior and posterior segments short, intersegmental grooves well defined; median segments long (as long or longer as wide). Integument mostly transparent, smooth, with minute papillae mainly near pygidium. Interramal papillae small, usually with a short stalk or sessile. Noto- and neurochaetae include uni- or bidentate aciculars, straight or falcate spinulose, and smooth capillaries in anterior and posterior regions. Median chaetigers with only one notoacicular chaeta. Pygidium non-retractile, often with small papillae, and large, falcate aciculars surpassing pygidial margin. Genital papillae unknown. Free living, sometimes in flexible, fibrous tubes, with or without foreign particles.

Etymology. The genus is named to honor the late Dr. Nathan W. Riser in recognition of his careful study of one fauveliopsid species, where he clarified some anatomical features, and discovered the presence of genital papillae. The genus name is a free combination of the last name with the Greek suffix – iopsis. This suffix refers to a certain appearance or resemblance, and it was originally used for the typhloscolecid Travisiopsis Levinsen, 1885 matching the original meaning. However, McIntosh (1922) used this suffix to name what would become the type genus for the family, Fauveliopsis , and Petersen (2000) followed for Laubieriopsis . The alternative would be Riserius , but it was already used by Norenburg (1993) for a nemertean, such that we prefer to follow the trend for naming genera in the family.

Remarks. Riseriopsis n. gen. resembles Laubieriopsis Petersen, 2000 by having smooth bodies with integument usually transparent; they differ in the general body shape and in chaetal patterns. In Riseriopsis n. gen. the body is swollen in both ends, usually more pronounced along the posterior region, and there are only acicular notochaetae in median region, whereas in Laubieriopsis the body is more or less cylindrical, not swollen in either end, and there are aciculars and capillaries in the notopodia of the median region.