Orbinia Quatrefages 1866

Genus Orbinia Quatrefages, 1866

Aricia Savigny, 1820: 12, 35–36. Preoccupied. Type-species: A. sertulata Savigny, 1820, by monotypy. Orbinia Quatrefages, 1866: 288. Type-species: Aricia cuvieri Audouin & Milne-Edwards, 1833 (= Aricia sertulata Savigny), designated by Hartman 1942.

Diagnosis. Prostomium conical, pointed; peristomium with 1 achaetous ring. Branchiae from thoracic setigers (5– 20). Posterior thoracic segments with postsetal lobes (2–many) and subpodial lobes (3–many), usually forming ventral encircling fringe of 5 or more lobes. Thoracic neurosetae including blunt uncini, crenulated capillaries and rarely subuluncini; heavy spear-like or brush-tipped spines absent. Abdominal neuropodia with flail setae.

Remarks. Species having a modified posterior thoracic region with spearlike spines are referred to the genus Phylo Kinberg in accordance with Hartman (1957) and Day (1973). Species of Phylo are, however, closely related to Orbinia species in overall morphology and are often treated as a subgenus of Orbinia. Results of recent molecular analyses (Bleidorn 2005; Bleidorn et al. 2009) confirm these findings.

To date, 20 species and subspecies of Orbinia sensu stricto are known with two new species recently described from offshore Brazil (Leão & Santos 2016). Most have branchiae from setiger 5–7, while a small group of three species have branchiae from setiger 8 or more posteriorly. A fourth species, belonging to the latter group has been discovered from intertidal sand sediments in Argentina. A single specimen of a species with branchiae from setiger 6 has been found in the South Shetland Islands on the Antarctic Peninsula and may represent another undescribed species. This specimen is described, but not named here due to the lack of sufficient material.