Petersenaspis

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 58-60

Petersenaspis sp. Figure 20

Sternaspis sp: Caullery 1944: 70.

Material examined.

Indonesia, Lesser Sunda Islands. 2 spec. (ZMA 1717), RV Siboga Exped., Sta. 300 (10°48.6'S, 123°23.1'E), 918 m, 30-I-1900. Philippines. 1 spec. (MNHN Musorstrom 3-94), Sta. 94 (13°47.4'S, 120°03.4'E), 780 m, 1-VI-1985.

Observations.

Two specimens (ZMA 1717), dried out. Longer, complete specimen (Fig. 20A) with introvert exposed, body wall breaking apart, 10 mm long, 3.3 mm wide. First three chaetigers with 10-12 bronze, subdistally expanded hooks (Fig. 20B). Ventro-caudal shield without sediment particles, longer than wide; anterior margins rounded, anterior depression shallow, lateral margins rounded (Fig. 20C); suture barely visible. Fan expanded beyond posterior corners, with median notch. Posterior region without branchiae, branchial plates not visible (Fig. 20D).

Smaller specimen (Fig. 20E) with introvert invaginated or broken off; body 5.8 mm long, 2.7 mm wide. Right ventro-caudal shield plate (Fig. 20F) with anterior and lateral margins rounded, fan with a median notch, with a smooth margin.

The other specimen (MNHN Musorstrom 3-94) with introvert invaginated; body 8 mm long, 5.5 mm wide. Ventro-caudal shield reddish with barely defined ribs and sediment particles removable by brushing. Chaetal fascicles better developed laterally, 10 bundles per side, and 6 posterior fascicles feebly developed per side.Branchiae lost, branchial plates barely projected, with abundant sediment particles.

Remarks.

Caullery (1944: 70) found two deep water specimens which were already corrugated and partly dehydrated when he observed them. The third specimen does not have the introvert exposed and the body wall is broken. These specimens belong to Petersenaspis because of several features: 1) the shield does not have well developed ribs, nor concentric lines on the surface, and 2) one of the Leiden specimens has spatulate introvert hooks. However, because of the state of the specimens, their complete description and affinities must wait until additional material becomes available. It can be indicated, however, that because of their shield shape, they resemble Petersenaspis capillata more than Petersenaspis palpallatoci , but because the Brazilian species was found in shallow water we think this is a different species.

Distribution.

Indonesia to the Philippine islands, 840-918 m depth.