Pseudopallene chevron, Staples, 2007

Staples, David A., 2007, Pycnogonids (Arthropoda: Pycnogonida) from the Great Australian Bight, southern Australia, with description of two new species., Memoirs of Museum Victoria 64, pp. 95-101 : 99

Pseudopallene chevron sp. nov.

Figure 2A–J

Material examined. 1 male, holotype, Waldergrave I., 25 m, 25 Oct 1973 SAM E 3681 .

Diagnosis. Trunk smooth, completely segmented. Post-ocular surface of cephalon evenly rounded, not divided longitudinally, mid-dorsal mound not present. Abdomen more or less tubular. Proboscis bullet-shaped, without constrictions, margins evenly curved and tapered towards tip. Oviger terminal claw scooped, margin lined with rounded teeth. Red chevron markings on trunk may be a useful diagnostic character.

Description. Leg span about 27.0 mm. Trunk smooth, completely segmented; neck region of cephalon sloping away from base of ocular tubercle; post-ocular surface evenly rounded, not divided longitudinally, mid-dorsal mound not present; length of lateral processes about 1.5 times maximum width, 1st and 2nd pair separated by about one-quarter of basal widths. Ocular tubercle with 2 prominent dorsal papillae, lateral sensory organs not evident; 4 eyes, darkly pigmented. Abdomen more or less tubular, constricted distally, cleft anal opening. Proboscis bullet-shaped, without constrictions, margins evenly curved and tapered towards tip, 3 lips prominent, extended, oral fringe not evident. Chelifore scape without basal constriction, chela fingers with linear cutting edge, length of moveable finger slightly less than length of palm, dorsal surface of immoveable finger with several strong setae on outer surface. Oviger 10-segmented, segment 5 longest, strongly curved, distal apophysis prominent, all segments covered in small, but strong, simple spines; compound spine formula segments 7 to 10, 14:11:10:10, terminal claw scooped, margin lined with 22–26 rounded teeth. 3rd leg: coxa 2, 2.5 times length of coxa 3, tibia 2 longest, femur longer than tibia 1, propodus with 4 strong heel spines, distal-most spine longest, greater than half width of heel, heel spines followed by 2 lesser spines followed by 10–15 much smaller sole spines. Genital pores round, tiny, on ventrodistal surface of legs 3 and 4.

Measurements of holotype (mm): trunk length (frontal margin of cephalic segment to tip of 4th lateral process), 3.5; width (across 2nd lateral processes), 1.55; proboscis length (dorsal), 1.20; 3rd leg: coxa 1, 0.55; coxa 2, 1.38; coxa 3, 0.55; femur, 3.05; tibia 1, 2.64; tibia 2, 3.75; tarsus, 0.25; propodus, 0.85; claw, 0.48.

Remarks. This small species is of a similar size to P. reflexa Staples, 2005 with which it shares the absence of a preocular mound and the longitudinal division of the cephalon. It otherwise differs in the arrangement of the propodal heel spines, the shape of the proboscis and abdomen and not having an irregular surface of the legs. The evenly rounded preocular region of the cephalon also resembles that of the much larger and more robust P. ambigua but from which it also differs conspicuously in the shapes of the proboscis, the chelifores, the oviger claw and the propodus. It is of interest to note that Bamber (2005: 332) records markings on the trunk and legs of P. ambigua from the Recherche Archipelago; a feature uncharacteristic of specimens from southeastern Australia where they are uniformly yellow. Photographs of live P. chevron show colour to be predominantly yellow with red markings. Although this preserved specimen has lost all trace of colour, dark V-shaped markings persist on the trunk and a median line extends dorsally along the lateral processes and femur. Bandings on the tibiae, the chelae and part of the cephalon indicate that these areas also were pigmented, perhaps providing useful diagnostic character in live material. This is a common species of Pseudopallene in South Australian waters (pers. com. Karen Gowlett-Holmes).

Distribution. Based on photographic records of live specimens, this species may be widely spread in SE Australia.

Etymology. Named for the V-shaped dorsal trunk markings (chevrons) which, in combination with the leg markings, appear to be a distinctive diagnostic character; a noun in apposition.

Figures

Figure 2 Pseudopallene chevron sp. nov. male holotype (SAM E3681): A, trunk, lateral; B, trunk, dorsal; C, trunk, anterior; D, leg 2; E, oviger; F, oviger claw; G, chela exterior; H, chela interior; I, abdomen lateral; J, tarsus and propodus leg 4.