Pseudopotamilla knightjonesae Tovar-Hernández, León-González & Bybee, 2017, sp. nov.

Pseudopotamilla knightjonesae sp. nov.

( Figs 28–30, 33 C)

Material examined. Type material: ARGENTINA, Holotype (UANL 8111), 8 paratypes (UANL 8112). Santa Clara del Mar, 37°50’30”S, 57°29’58”W, intertidal, 18 January 1968, coll. J.M. Orensanz. Additional material: ARGENTINA, UANL 8113, 20 topotypes; UANL 8114: Mar del Plata, Frentemar, 37°52’15”S, 57°30’48”W, intertidal, 23 December 1968, coll. J.M. Orensanz, dried tubes (40 tubes); UANL 8115: Santa Elena, 37°52’15”S, 57°30’48”W, intertidal, 27 January 1971, coll. J.M. Orensanz, 1 specimen; UANL 8116: Cerro Avanzado, Restinga del SW, 10 January 2008. coll. J.M. Orensanz & M. Orensanz, 1 specimen.

Description. Trunk length 12 mm (4–8 mm), width 0.5 mm (0.3–0.5 mm). Branchial crown length 1.5 mm (1– 2 mm), with six pairs of radioles. Seven thoracic segments (6–11 segments). Abdominal segments 53 in one paratype (holotype and other paratypes lack posterior abdomens). Radiolar flanges and palmate membrane both Species Number of Miđ-đorsal margins of Anterior peristomial Ventral lappets of collar Dorsal, glanđular Pygiđial eyes Habitat

compounđ eyes collar ring shielđs on 2nđ (rađiole 1: đorsal thoracic segment most)

absent. Long pinnules arranged in two alternating rows decreasing in length distally; radiolar tips short, as long as space of 2–4 pinnules (Fig. 29 C). A large compound eye located proximally in second dorsal radioles (Fig. 29 A, B). Branchial lobes short (Fig. 28 A), with dorsal and ventral flanges: dorsal pair triangular (Fig. 28 D), ventral pair rounded (Fig. 28 D). Collar with dorsal margins triangular, short, fused to faecal groove; V-shaped dorso-lateral incisions (Fig. 28 A, C, D; 29A, B, D). Anterior peristomial ring exposed partially dorsally and laterally (Figs 28 C, D, 29A, B, D). Ventral collar lappets triangular, short, separated mid-ventrally by depth incision (Fig. 28 B). Dorsal and ventral lips not examined. Two dorsal pinnular appendages present; two ventral radiolar appendages. Ventral sacs present. Ventral shield of chaetiger 1 entire, rectangular with rounded anterior margin (Fig. 28 B). Chaetiger 1 notochaetae in two rows, broadly-hooded. Thoracic shields rectangular, divided transversely (Fig. 28 B). Thoracic neuropodial tori separated from ventral shields by broad gap (Fig. 28 B). Superior thoracic notochaetae elongate narrowly-hooded; inferior group paleate (Fig. 30 D), arranged in two rows, with long and pointed mucro. Thoracic neuropodia with avicular uncini with several rows of small and similarly-sized teeth above main fang; breast well developed, handles twice the length of main fang (Fig. 30 F, G). Companion chaetae with asymmetrical membrane and long handles, slightly longer than uncinial handles (Fig. 30 H). Abdominal neurochaetae elongate broadly hooded (Fig. 30 E). Notopodia with uncini with several rows of teeth above main fang on two thirds of its length, breast well developed and handle short (Fig. 30 I). Pygidium bilobed (Fig. 30 C), eyes absent. Tubes covered with sand grains (Fig. 30 A), or embebed in hard sediment matrix (Fig. 30 B).

Type locality. Argentina, Santa Clara del Mar, 37°50’30”S, 57°29’58”W, intertidal.

Etymology. The species is named after Dr. Phyllis Knight-Jones, in recognition for her vast research on sabellid polychaetes and also for her approval to send the sabellid collection from South America to the first author.

Remarks. Pseudopotamilla knightjonesae sp. nov., is unique by boring into hard sediment matrix and by having a single, large compound eye, located proximally on second dorsal radioles. Pseudopotamilla platensis is distinguishable from P. knightjonesae sp. nov., by the presence of 2–3 eyes in each dorsal radioles 2 and 3 versus only one large compound eye located in dorsal radioles 2 in P. knightjonesae sp. nov. In P. platensis, the mid-dorsal collar margins are long and triangular (short in P. knightjonesae sp. nov.). The ventral lappets of collar are even, forming right angles divided by a short incision in P. platensis, against ventral lappets triangular, divided by a depth incision in P. knightjonesae sp. nov. Finally, P. platensis was found in soft bottoms, whereas P. knightjonesae sp. nov. was found boring rocks in the intertidal zone (Table 4).

Pseudopotamilla knightjonesae sp. nov., differs from P. reniformis from the White Sea for the following features: mid-dorsal collar margins triangular (rounded in P. reniformis); ventral lappets of collar triangular, divided longitudinally by a depth incision (rounded, shallow, divided longitudinally by a short incision in P. reniformis) and absence of pygidial eyes (present in P. reniformis) (Table 4).