Petersenaspis harrisae, Salazar-Vallejo, 2017

Salazar-Vallejo, Sergio I., 2017, Cymonomus curvirostris Sakai 1965, Zoological Studies (Zool. Stud.) 56 (32), pp. 16-16 : 5-7

Petersenaspis harrisae sp. nov.

( Fig. 3 )

urn:lsid:zoobank.org:act:A157B737-7606-487E-9893-2B6E87B2F35F

Type material: Southwestern Indian Ocean , South Africa. Holotype ( LACM 5691 ) and two paratypes ( LACM 5692 ), off Durban, International Indian Ocean Expedition, R.V. Anton Bruun, Cruise 7, Sta. 356B (29°11'S, 31°37'E), rock dredge, 15 m, 29 Jul. 1964 (paratypes 2.5-7.0 mm long, 1.5-4.0 mm wide; shield reddish in smaller one, purple in larger one, left shield plate 0.7-2.0 mm long, 0.5-1.5 mm wide).

Additional material: Southwestern Indian Ocean, Madagascar. Three specimens ( LACM 5694), one with introvert partly exposed, shield dark reddish to purple, ribs visible but without concentric lines; off Tulear, International Indian Ocean Expedition, R.V. Anton Bruun, Cruise 7, Sta. 363S (23°18'S, 43°36'E), Campbell grab, 33 m, 4 Aug. 1964 (8.0- 8.5 mm long, 4.5-5.0 mm wide; left shield plate 1.8-1.9 mm long, 1.3- 2.0 mm wide). One specimen ( LACM 5693), complete, distorted by compression, inner organs macerated, introvert and anal peduncle exposed, shield dark purple, right plate broken, without concentric lines; off Tulear, International Indian Ocean Expedition, R.V. Anton Bruun, Cruise 7, Sta. 363U (23°19'S, 43°35'E), Campbel grab, 128 m, 6 Aug. 1964 (16 mm long, 4 mm wide, abdomen 10 mm long, left shield plate 2 mm long, 1.4 mm wide; chaetiger 3 with 17 hooks per bundle). Four specimens ( MNHN 860), near Tuléar, Sta. Unnumb. (23°32.2'S, 43°35.8'E), dredge, 300 m, 20 Feb. 1973, C. Jouannic, coll. Very damaged, rotten, shields detached, like if taken from a fish’s stomach contents. The shield is reddish with well-developed ribs, but no concentric lines; there is no deep notch close to the posterior corners. However, the introvert hooks are subdistally expanded and the specimens belong to an undescribed Petersenaspis species. It is interesting to note that shield surface papillae, which usually give it a velvety appearance, were removed, probably by erosion or by digestion, although there is no indication that it was taken from a fish stomach.

Description: Holotype ( LACM 5691) complete; introvert body wall slightly broken. Body whitish, integument granulose with small abundant papillae covering most of body ( Fig. 3A ). Introvert slightly darker; introvert spines bronze; shield purple; introvert with more sediment particles; posterior lateral chaetal bundles with chaetae longer than body length.

Prostomium projected, blunt, conical ( Fig. 3B ). Peristomium rounded, equalized to the position of mouth, with papillae abundant in mouth area, not extended beyond it. Mouth circular, extended from base of prostomium to anterior edge of first chaetiger.

First three chaetigers with 13-15 dark bronze, recurved spatulate hooks, without subdistal dark areas ( Fig. 3B ). Genital papillae not visible (small digitate in LACM 5694). Pre-shield region with 8 segments; lateral bundles of 2 capillary chaetae protruding from body wall along segments 9-12.

Shield purple, finely papillose, with ribs faintly defined but no concentric lines ( Fig. 3C ), nor sediment particles; suture extended throughout shield. Anterior margins rounded, anterior depression deep; anterior keels not exposed. Lateral margins rounded, expanded medially, reduced posteriorly. Fan truncate, barely projected beyond posterior shield corners, margin smooth, with a median notch.

Marginal shield chaetal fascicles include 10 lateral ones, chaetae in oval arrangement, and 10 posterior fascicles, chaetae in oval arrangement. First two posterior fascicles with very long, delicate chaetae; other fascicles with fewer, shorter chaetae. Peg chaetae not well-defined.

Branchiae scarce, arranged in 1-2 series, emerging from a distinct depression (flat in other specimens); branchial area with a projected ridge, with abundant delicate interbranchial papillae, better preserved towards margin of shield ( Fig. 3G ).

Variation: The intensity of pigmentation varies during ontogeny. Smaller paratype has a reddish shield ( Fig. 3E ), and chaetae paler, whereas the larger paratype has a darker shield ( Fig. 3F ), and additional specimens having their introvert partly exposed, show darker introvert hooks.

Etymology: This species is being named after my good friend and teacher, Leslie Harris, collection manager of the Allan Hancock Foundation polychaete collection in LACM, as a modest means to acknowledge her long standing support for my research activities. The epithet is a noun in the genitive case.

Remarks: Petersenaspis harrisae sp. nov. resembles P. palpallatoci Sendall & Salazar-Vallejo, 2013 from the Philippine Islands because both have shields with anterior margins projected forward. As indicated in the key below, they differ because in P. harrisae the fan has a median notch but no lateral notches, and ribs are barely defined, whereas in P. palpallatoci the fan has both, median and lateral notches, and ribs are well defined. In her analysis of the IIOE materials, Hartman (1974:199) recognized at least four different sternaspids but she did not include the current specimens.

Distribution: Only known from two localities in the Southwestern Indian Ocean, between South Africa and Madagascar, in sediments at 15-128 m depths.

Figures

Fig. 3. Petersenaspis harrisae sp. nov. (A) Holotype (LACM 5691), oblique lateral view. (B) Same, anterior end, frontal view. (C) Same, shield, slightly dislodged, frontal view. (D) Larger paratype (LACM 5692), frontal view. (E) Smaller paratype (LACM 5692), shield, frontal view. (F) Larger paratype, shield. (G) Same, branchial plate, left side without branchiae, papillae or sediment particles. Scale bars: A, D = 1 mm, B, E = 0.25 mm, C, G = 0.5 mm, F = 0.7 mm.