Genus Oligobregma Kudenov & Blake, 1978

Type-species: Pseudoscalibregma aciculatum Hartman, 1965, designated by Kudenov & Blake 1978.

Diagnosis. Body elongate and arenicoliform. Prostomium T-shaped with two prominent frontal horns; eyes present or absent; nuchal organs present. Peristomium achaetous, surrounding prostomium dorsally and forming upper and lower lips of mouth ventrally. Branchiae absent. Parapodia with well-developed dorsal and ventral cirri on posterior segments; interramal papilla present or absent. Large acicular spines present on anterior setigers. Capillaries present in all parapodia; lyrate setae present anterior to capillaries of setigers 2, 3, or 4; some species with short, slender, blunt or pointed spinous setae anterior to capillaries of setigers 1, 2 or 3, representing homologues of lyrate setae. Pygidium with anal cirri.

Remarks. Oligobregma is one of four genera with dorsal and ventral cirri: Scalibregma (with branchiae and without large anterior acicular spines); Sclerobregma (with branchiae and with large anterior acicular spines); Pseudoscalibregma (without branchiae or large anterior acicular spines); and Oligobregma (without branchiae and with large anterior acicular spines). The boundaries between these genera are not great and since the presence and absence of branchiae and large anterior acicular spines are characters occurring in other genera, it is obvious that the generic arrangement of scalibregmatids should be revised. In addition, the observations in this paper of branchiae developing late in juvenile Scalibregma australis n. sp. ontogeny means that they pass through a Pseudoscalibregma -like phase where the genus (and species) cannot be confirmed. A similar situation has been identified with Sclerobregma branchiatum in the western North Atlantic, where juveniles lacking branchiae were initially thought to represent a new species of Oligobregma (Blake & Luzak unpublished).

However, for the time being the definition of these genera and others provide a practical way to use a suite of characters to classify and identify them with the caveat that small specimens thought to be one genus might be a juvenile of another. At present, ten species have been described as Oligobregma, all except one from the southern ocean and hemisphere:

Oligobregma aciculata (Hartman, 1965) . Western North Atlantic

Oligobregma blakei Schüller & Hilbig, 2007 . Antarctica, Scotia Sea, 2889‒2892 m. Juvenile, possibly belongs to a different genus.

Oligobregma collare (Levenstein, 1975) . Subantarctic and Antarctic seas, 1622‒6070 m.

Oligobregma hartmanae Blake, 1981 . Antarctica, Weddell Sea, 505 m. Here referred to the genus Pseudoscalibregma .

Oligobregma lonchochaeta Detinova, 1985, North Atlantic, Reykjanes Ridge.

Oligobregma notiale Blake, 1981 . Antarctica, widespread, shallow water to over 900 m.

Oligobregma oculata Kudenov & Blake, 1978 . Off New Caledonia, 57 m.

Oligobregma pseudocollare Schüller & Hilbig, 2007 . Antarctica, Scotia and Weddell Seas, 753‒3050 m.

Oligobregma quadrispinosa Schüller & Hilbig, 2007 . Antarctica, Scotia and Weddell Seas, 2258‒4069 m.

Oligobregma simplex Kudenov & Blake, 1978 . SE Australia, Westernport Bay, 11 m.

Of these species, all except O. hartmanae and O. blakei are validly placed in Oligobregma . O. hartmanae has only small spines in setigers 1‒2 anterior to and smaller than the accompanying capillaries. These represent the small spinous setae that are considered to be homologues of lyrate setae that occur from setiger 3 and are not the large heavy acicular spines of other species. The short spinous setae have now been observed in many species in which they were not originally described. O. hartmanae is therefore referred to the genus Pseudoscalibregma . Oligobregma blakei is described from a very small specimen only 3 mm in length and less than the size where branchiae developed in Scalibregma australis n. sp. (see above) and may not be validly placed in Oligobregma . A new species of Oligobregma has been discovered in the LIS-A area and is described herein.