Sternaspis maior Chamberlin, 1919

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 36-38

Sternaspis maior Chamberlin, 1919 Figure 11 A–G

Sternaspis maior Chamberlin, 1919: 406-407, Pl. 78, fig. 10.

Sternaspis fossor : Fauchald 1972: 238-239, Méndez 2007: 609, 614, 616 fig. 7 (partim, non Stimpson 1853).

Type material.

Eastern Tropical Pacific, Gulf of California. Neotype (UNAM 7882), RV El Puma, Crucero Talud V, Sta. 25 (24°52'N, 108°58'W), off Isla Altamura, Sinaloa, 830 m, 16-XII-2001, N. Méndez, coll. 1 paraneotype (UNAM 7881), RV El Puma, Crucero Talud V, Sta. 18 (24°15'N, 108°17'W), off Ensenada del Pabellón, Sinaloa, 965 m, 15-XII-2000, N. Méndez, coll. 1 paraneotype (UNAM 0000), RV El Puma, Crucero Talud XIV, Sta. 13 (28°31'34"N, 112°17'43"W), dredge, 180-182 m, 8-IV-0000, B. Yáñez, coll.

Description.

Neotype (UNAM 7882), with body browinish, paler without the papillar layer (Fig. 11A, B). Introvert expanded, markedly wider than abdomen, covered with abundant small papillae. Abdomen with abundant, homogeneously distributed papillae. Body 17 mm long, 6 mm wide (complete paraneotypes 19.5-20.0 mm long, 7-10 mm wide), about 29 segments.

Prostomium hemispherical, paler than surrounding areas (Fig. 11C). Peristomium round, without papillae. Mouth oval, covered by papillae, restricted to a circular region around the mouth.

First three chaetigers with 12-14 golden, widely separated, falcate introvert hooks per bundle, each with subdistal dark areas (Fig. 11B, C). Genital papillae lost, eroded from the intersegmental groove between segments 7 and 8.

Pre-shield region with 7 segments, with papillae abundant, evenly distributed. No capillary chaetae seen.

Ventro-caudal shield with ribs, but no concentric lines; suture restricted to anterior region. Anterior margins rounded; anterior depression shallow; anterior keels not exposed (Fig. 11A, D). Lateral margins gently rounded, expanded posteriorly. Fan truncate, not extended beyond posterior shield corners, with a median notch, crenulated.

Marginal chaetal fascicles include 10 lateral ones (Fig. 11B, D), chaetae ovally arranged and 8 posterior fascicles, chaetae in linear arrangement. Peg chaetae on conical extensions emerging under shield corners. Peg chaetae with stout base in cross section; a small fascicle of delicate capillary chaetae (peg-associated capillary chaetae) between peg chaetae and first fascicle of posterior chaetae.

Branchiae numerous, thick, coiled, slender, long, protruding from two oval plates, separated by a wide angle, on either side of the anus. Additional fine, long filamentous papillae extending along the posterior margin of the shield.

Variation.

The shield varies from dark reddish to orange (Fig. 11 E–G) although their relative width varies depending on how heavily contracted the abdomen is, and how this contraction bends the lateral plates dorsally resulting in an apparently narrower looking shield. The main radial rib is very prominent, the fan is crenulated but it may be truncate, barely reaching the posterior corners (Fig. 11E, F), or projected beyond this corners (Fig. 11D, G).

Neotype locality.

Off Isla Altamura, Sinaloa, Gulf of California, 830 m depth.

Remarks.

Sternaspis maior Chamberlin, 1919 was very briefly described and the main distinguishing features were based upon the shield. Judging from the dimensions of the ventro-caudal shield (7 mm long, 15 mm wide), the original specimen must have been very large, but perhaps his specimen was severely damaged and only the shield could be characterized.

It is noteworthy that Chamberlin and Augener (1918, for Sternaspis africana , see above) almost simultaneously based their descriptions on schematic shield illustrations. Both illustrations indicate significant resemblances to the specific shields shape and ornamentations of Sternaspis maior . In both species, the shield was illustrated as having no concentric lines; for Sternaspis maior , the anterior depression had large keels, the main radial rib is quite distinct, and the fan has a median notch. These features are all present on the neotype such that we are confident we found the same species, and that this species is distinct. Thus, in order to clarify its taxonomic status ( ICZN 1999, Art. 75.3.1), a neotype has been selected, described and its diagnostic features have been illustrated ( ICZN 1999, Art. 75.3.2-75.3.3). Hartman (1938: 3) emphasized that many type specimens which were supposedly deposited in Harvard, were not found in the collections and this includes the type materials of Sternaspis maior , such that we can conclude there is no type material available ( ICZN 1999, Art. 75.3.4). We regard the neotype as conspecific with the specimen described in the original description ( ICZN 1999, Art. 75.3.5). The original type locality was from the Gulf of California, south of Guaymas, Sonora (27°39'40"N, 111°00'30"W), 1143 m, and the proposed neotype was collected in a nearby locality, along the eastern Gulf of California coast, and in similar depths to the original material ( ICZN 1999, Art. 75.3.6). The neotype and paraneotypes are deposited in the Marine Benthic Invertebrates Reference Collection of the Mazatlán Academic Unit, UNAM ( ICZN 1999, Art. 75.3.7).

Sternaspis maior resembles Sternaspis affinis because both species have shields with round anterior margins, fan projected beyond the level of the posterior corners and with a median notch. The main difference relates to the presence of concentric lines which are barely visible in Sternaspis maior and distinct in Sternaspis affinis .

Distribution.

Central part of the Gulf of California, México, in soft bottoms at 180-965 m, but the original material was collected at 1143 m.