Petersenaspis deani, Salazar-Vallejo, 2017

Salazar-Vallejo, Sergio I., 2017, Cymonomus curvirostris Sakai 1965, Zoological Studies (Zool. Stud.) 56 (32), pp. 16-16 : 4-5

Petersenaspis deani sp. nov.

( Fig. 2 )

urn:lsid:zoobank.org:act:471AAF07-4730-4D27-9CF9-8849C0DEFA51

Sternaspis scutata : Vargas et al. 1985:337; Maurer et al. 1988:48; Dean 1996:75 (non Ranzani, 1817, partim).

Type material: Eastern tropical Pacific, Costa Rica. Holotype ( USNM 80322 ) and five paratypes ( USNM 1437648 ), Golfo de Nicoya, Sta. 31-2 (09°44'00"N, 84°59'25"W), 22 m, 10 Jul. 1980, H.K. Dean, coll. (paratypes 6-10 mm long, 2-3 mm wide, abdomen 4.0- 6.5 mm long; left shield plate 0.7-1.1 mm long, 0.6-1.1 mm wide; 14-16 introvert hooks per bundle).

Description: Holotype ( USNM 80322) with body whitish, shield deep red ( Fig. 2A ); body papillae globose, scarce and small filamentous papillae throughout body. Larger, thin abundant papillae in dorsal surface of posterior end, surrounding the shield. Body 7 mm long, 3 mm wide, abdomen 4 mm long, about 30 segments.

Prostomium hemispherical whitish, opaque, projected, with a transverse depression, as large as mouth ( Fig. 2B ). Peristomium rounded, with abundant papillae over the mouth, extended behind prostomium. Mouth circular, extends from base of prostomium to anterior edge of first chaetiger.

First three chaetigers with 14-16 golden recurved, thin spatulate hooks, without subdistal dark areas. Genital papillae short, thick, blunt, protrude ventrally from body wall between segments 7 and 8. Pre-shield region with 8 segments, segments 9-13 with mostly single capillary chaetae.

Shield deep red, papillose, with ribs faintly defined but no concentric lines, sediment particles easily removed from shield ( Fig. 2C ); suture extended throughout shield. Anterior margins rounded; anterior depression very shallow; anterior keels not exposed. Lateral margins rounded, expanded medially, reduced posteriorly. Fan truncate, barely projected beyond posterior shield corners, margin smooth, with shallow median notch.

Marginal shield chaetal fascicles include 11 lateral ones, chaetae of each fascicle in oval arrangement, and 10 ill-defined posterior fascicles, each with 1-2 chaetae. Last lateral fascicle with longer chaetae. Peg chaetae or additional chaetae not present.

Branchial filaments abundant, helicoid, not emerging from a branchial plate. Interbranchial papillae abundant, more or less straight, delicate, ½-⅓ as long as branchiae.

Variation: Paratypes with shields reddish, similar to holotype in general outline; the paratype follows the general pattern bur its lateral margins tend to be more curved, and individual plates become wider than long ( Fig. 2D ). The same specimen has a poorly defined, longer than wide branchial plate with 3 series of oblique branchial scars ( Fig. 2E ).

Etymology: This species name is after Dr. Harlan Dean, in recognition of his many useful publications about Central American polychaetes, and especially because he collected the specimens used for the description. The epithet is a noun in the genitive case.

Remarks: Petersenaspis deani sp. nov. r e s e m b l e s P. c a p i l l a t a (Nonato, 1968) as redescribed elsewhere ( Sendall and Salazar-Vallejo 2013), because both species have shields with anterior depression shallow, and fans with a median notch. They differ in the relative color and number of introvert hooks per series; in P. deani introvert hooks are golden and more abundant (14- 16), than in P. capillata where they are bronze and fewer (about 10). The fact that the type material of P. deani is generally smaller, has more introvert hooks than the corresponding one for P. capillata , and their discontinuous distribution, being one present in the Pacific coast of Costa Rica, whereas the other one thrives in Brazil, indicate they are different species.

Distribution: Only known from the type locality, Gulf of Nicoya, Costa Rica, in sediments at 22 m depth.

Figures

Fig. 2. Petersenaspis deani sp. nov. (A) Holotype (USNM 1437648), ventral view. (B) Same, anterior end, frontal view. (C) Same, shield. (D) Largest paratype (USNM 1437648), shield. (E) Same, branchial plate after removal of branchial and interbranchial filaments. Scale bars: A = 1 mm, B, D, E = 0.4 mm, C = 0.3 mm.