Petta assimilis McIntosh, 1885

Zhang, Jinghuai, Hutchings, Pat & Kupriyanova, Elena, 2019, A revision of the genus Petta Malmgren, 1866 (Annelida: Pectinariidae), with two new species from deep waters of southeastern Australia, and comments on phylogeny of the family, Zootaxa 4614 (2), pp. 303-330 : 311-312

Petta assimilis McIntosh, 1885

Petta assimilis McIntosh, 1885: 423–424 , pl.47, figs 8–9, pl. 26a, figs 16–19 (between Prince Edward and Kerguelen Island, 46º16´S, 48º27´E, 2926 m). Petta assimilis— Branch 1994:15 (Prince Edward Island).? Petta assimilis— Hartman 1967: 151–152, pl. 44 (off Cape Horn 1806–2013 m and Falkland Islands, 2452 m, South Ameri- ca).

Description. Single specimen without tube collected by dredge from 2926 m depth, measuring 22 mm in length and 4.4 mm in diameter. About 14 pairs of golden paleae, long and slender, inner ones thinner. Margins of cephalic veil smooth. Scaphe with a short and conical ligula, anal process (anal flap) forms a scale-like appendage to scaphe. Seventeen pairs of notopodia with notochaetae arranged in two rows, one with stout shafts and tapering tips with winged margins frayed towards tips appearing as double series of spikes; other one also winged with tip with basal heel and serrated tips (fig. 17 of McIntosh, 1885). Scaphal hooks stout with slightly curved blunt tips.

Distribution. Southern Indian Ocean: between Prince Edward and Kerguelen Island ( Fig. 1 , Table 2 );

Habitat. Type found at 2926 m depth, no information on sediments available.

Remarks. The holotype of P. assimilis McIntosh, 1885 lodged in Natural History Museum, London has been lost (Muir pers. comm.), so the above description is based on McIntosh’s (1885) original description. However, the description is very brief and incomplete, it includes figures of anterior and posterior ends and notochaetae and neurochaetae, but mentions nothing about the glandular areas of the body. McIntosh compares his species to the “British species representative” of the genus and comments that his new species has scaphal hooks resembling those of a mysterious British species (never subsequently described) and Petta pusilla .

Hartman (1967) described two specimens from the abyssal sub-antarctic areas off Cape Horn and Falkland Islands in South Atlantic Ocean as P. assimilis . These specimens are similar to P. assimilis as they both have a continuous row of lappets on the ventro-lateral lobes of segment 3. However, Hartman (1967) states that these specimens have a short anal cirrus, seven lappets on each ventro-lateral lobe of segment 2 and pair of long mid-ventral lappets on segment 3, characters that are difficult to compare with the brief original description. She also mentioned three pairs of branchiae with the first pair of branchiae being simple and cirriform, which we suggest may represent tentacular cirri because all pectinariids have only two pairs of lamellate branchiae on segments 3 and 4. By comparing descriptions and illustrations alone we cannot ascertain whether Hartman’s material belongs to P. assimilis , and it seems unlikely on biogeographical grounds.

Branch (1994) gives a key to polychaetes, including Petta assimilis , from Prince Edward Island in southern Indian Ocean. This material collected close to the type locality is deposited in Iziko South African Museum in Cape Town (pers. comm. Albe Bosman) and needs to be examined.

Figures

FIGURE 1. Type localities of all Petta species.