Pallenella difficile ( Arango, 2009 )

Staples, David A., 2025, Pycnogonids, ‘ sea-spiders’ (Arthropoda, Pycnogonida) selected from the collections of the South Australian Museum with descriptions of new species and review of the genus Pallenella., Memoirs of Museum Victoria 84, pp. 1-47 : 32-34

Pallenella difficile ( Arango, 2009) .

Figure 10a–d. Plate 12a–h.

Pseudopallene difficile Arango, 2009: 9–11 , Fig. 4.

Meridionale difficile Staples 2014b: 346 [in list].

Pallenella difficile Brenneis et al, 2020: 854 [in key].

Material examined. Holotype. Ovigerous male ( WAM T92361 ). Western Australia, Houtman Abrolhos, CSIRO station 092-029, 28.9714°S, 113.8320°E to 28.9744°S, 113.8350°E, Sherman Sled , hard bottom, 86 m, 3 Dec 2005.

Figure 10. Pallenella difficile Arango (2009) , male, holotype WAM T92361. a, b, cephalon lateral and anterior views; c, propodus of detached leg; d, left chela.

Plate 12. Pallenella difficile Arango (2009) , male, holotype ( WAM T92361 ): a–b, trunk dorsal and lateral views; c, trunk dorsal, alternative view; d, trunk anterior view; e; proboscis and chelae; f, chelae; g, detached leg; h, propodus .

Diagnosis. Pre-ocular surface of cephalon rounded, longitudinal cuticular division absent. Proboscis with dorsal mid-constriction, most evident in lateral view, dorsodistal surface particularly bulbous before tapering to rather elongate jaw region, jaws with setiferous fringe. Neck short in dorsal view, not defined in lateral view. Chela slender, not strongly curved, immoveable finger cutting edge smooth, moveable finger with strong median protuberance. Legs without irregularities, propodal heel well-developed, with group of about eight prominent spines, claw slender, curved similarly along both margins. Eight indistinct eye lenses.

Remarks. A few additional comments are made to compliment the original description. The proboscis has a strong dorsal constriction at about one-third its overall length dividing two inflated parts before tapering to a rather elongate terminal part and jaws (plate 12b, d). The ventral surface of the proboscis is without an obvious constriction. The dorsodistal-most inflated part is accentuated by a dorsomedian blister-like swelling. This swelling is found in several other species also and is most apparent in lateral view where dissimilarities in the dorsal and ventral surfaces are evident. The jaws are surrounded by a setiferous fringe. In lateral view, the anterior margin of the eye tubercle slopes to the base of the crop without evidence of a defined neck (fig.10a, plate 12b). The legs are without peculiarities or irregularities. The original diagnosis of this species described the propodal heel as not prominent and with four strong spines ( Arango 2009: 9) but the propodus of the holotype agrees more so with figure 5B in that paper, which shows a prominent heel with a random group of about ten spines. Only two legs (both detached) have the propodus intact and in both cases the claw has an irregular shape (fig.10d, plate 12h). The claw and propodus are connected by a wide membrane. Two lenses are evident in some eyes while others are less distinct (Plate 12d). Eight eye lenses are recorded here for the species.