Petersenaspis palpallatoci, Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 57-58

Petersenaspis palpallatoci sp. n. Figure 19

Type material.

Philippine Islands, Sibuyan Sea. Holotype (MNHN 1551) and paratype (MNHN 1552), MUSORSTROM, Cruise 3, Philippines, Sta. 140 (11°42.6'N, 122°31.5'E), E off Kalibo, 93 m, 6-VI-1985 (paratype with introvert invaginated).

Additional material. Malasya. 1 spec. (AM W196245), Sarawak, Bintulu, Similajan National Park, Sta 6, 5.5 m, 1982.

Description.

Holotype (MNHN 1551) with body pinkish anteriorly, whitish medially and posteriorly, clean with sparse, small filamentous papillae covering most of body (Fig. 19A). Larger, thin papillae along the dorsal surface of last few segments and surrounding shield but not arranged in rows. Body 11 mm long, 3 mm wide, 32 segments.

Prostomium projected, blunt conical (Fig. 19A, B). Peristomium rounded, equalized to the position of mouth, with abundant papillae extended behind prostomium. Mouth circular, extends from base of prostomium to anterior edge of first chaetiger.

First three chaetigers with 12-14 bright bronze recurved, spatulate hooks, without subdistal dark areas (Fig. 19B). Genital papillae protrude ventrally from body wall between segments 7 and 8. Pre-shield region with 8 segments, with single lateral bundles of about 2 capillary chaetae, protruding from body wall along segments 9-10.

Ventro-caudal shield brick red, papillose, with ribs faintly defined but no concentric lines, nor sediment particles; suture extended throughout shield. Anterior margins rounded; anterior depression shallow; anterior keels not exposed. Lateral margins rounded, expanded medially, reduced posteriorly. Fan truncate, barely projected beyond posterior shield corners (Fig. 19A, C), margin smooth, with a median and two smaller lateral notches.

Marginal shield chaetal fascicles include 10 lateral ones, chaetae in oval arrangement, and 10 posterior fascicles, chaetae in oval arrangement. The 11th lateral fascicles include one or two fine capillary chaetae, four times as long as others. Posterior fascicles positioned close to midline. Peg chaetae broken; additional delicate capillary chaetae between lateral and posterior fascicles present.

Branchiae few, emerging from a distinct plate; branchial area (observed in paratype) covered with very thin, long interbranchial papillae, increasing in density towards margin of ventro-caudal shield (Fig. 19E).

Variation.

Both the paratype and additional specimen have their introvert invaginated. Their shields show progressive enlargements of the anterior margins and the fan, with the median and lateral notches becoming more pronounced (Fig. 19D), and the shield taking a more elongate outline.

Etymology.

This species name is after Virgilio S. Palpal-latoc, researcher of the National Museum, Manila, in recognition of his many publications on the polychaete fauna of the Philippine Islands. The epithet is a noun in the genitive case.

Remarks.

Petersenaspis palpallatoci sp. n. resembles Petersenaspis capillata (Nonato, 1966) because both have shields with abundant long papillae, poorly defined ribs and no concentric lines. They differ in the shape of their shields. In Petersenaspis palpallatoci the anterior margins are more projected forward and its posterior margin has a shallow median notch plus two lateral notches, whereas in Petersenaspis capillata the anterior margin is barely projected forward and the posterior margin has a median notch, but no lateral notches. There are other differences regarding the relative number of shield chaetal fascicles, but because of chaetal fragility, they are less reliable.

Distribution.

Philippine Islands to Malasya, in 5.5-93 m depth.