(Fig. 1 A–F)
Sabella oatesiana.— Monro 1936: 187 –188.
Sabella oatesiana.— Hartmann-Schröder 1983: 273.
Material examined. ARGENTINA, Campaña SAO V, UANL 8006, Golfo de San Matías, St. 213, 40°54’S (longitude coordinates lost), off Primer Camino, 28 m depth, 2 March 1973, coll. J.M. Orensanz, 1 specimen.
Description. One specimen incomplete (abdomen missing). Thorax with nine thoracic segments; 1.5 mm width. Branchial crown 5 mm long with 7 pairs of radioles. Narrow flanges along radiolar lengths. Radioles with brown band at 1/2 of branchial crown length and one pair of compound eyes located within this band (Fig. 1 D, E). Radiolar tips short, as long as space equivalent of origin of five pinnules (Fig. 1 D, F). Lateral collar margins even (Fig. 1 C). Dorsal collar margins not fused to faecal groove (Fig. 1 B). Anterior peristomial ring visible dorsally. Ventral collar lappets rounded, not overlapping (Fig. 1 A). Ventral shield of chaetiger 1 W-shaped (typical of Bispira), other thoracic shields rectangular (Fig. 1 A). Tube covered by fine sand, flexible.
Remarks. Bispira oatesiana (Benham, 1927) originally described from off Oates, Antarctica, does not present radiolar eyes (Knight-Jones & Perkins 1998). Sabella oatesiana sensu Monro, 1936 (Discovery report, RSS William Scoresby, 45°07’S, 64°54’N, off North of Golfo de San Jorge, Argentina), cannot be assigned to B. oatesiana since it has compound eyes. Sabella oatesiana sensu Hartmann-Schröder (1983) from Argentine Patagonian shelf (65–85 m depth) is the same species as that of Monro (1936) and the specimens reviewed here, from Golfo de San Matías, but different from that of Benham (1927). Features described in the three species by Monro, Hartmann-Schröder and the specimen in this study (Bispira sp.) match perfectly except that the number of eyes is quite variable, but this variation is common among Bispira species. Monro (1936) reported a number of scattered eyespots varying widely in number and distribution among 4 specimens: in one they form two fairly conspicuous irregular bands and in another specimen there are two or three scattered spots that can only be found after careful searching. In contrast, Hartmann-Schröder (1983) reported one pair of eyes per radiole, similar to the specimen examined here. Thus, we consider this specimen a new species, but we do not name it because only one incomplete specimen is available.
The main difference among the specimen from Gulf of San Matías (Argentina) and Bispira klautae, from Rocas Atoll (Brazil) is that the latter has dorsal, spongy cushion-like masses in the thoracic region (absent in the Bispira specimen from Argentina) (Fig. 1 B).