Forsteropsalis pureora, Taylor, Christopher K., 2013

Taylor, Christopher K., 2013, Further notes on New Zealand Enantiobuninae (Opiliones, Neopilionidae), with the description of a new genus and two new species, ZooKeys 263, pp. 59-73 : 63-65

Forsteropsalis pureora sp. n. Figure 2

Holotype.

♂. New Zealand, TO. Pureora, Waipapa Reserve, 570 m, 15 December 1983, J. Hutchinson, malaise trap in shrublands.

Etymology.

Named for the type locality.

Diagnosis.

The genus Forsteropsalis was established and revised by Taylor (2011). In the key to Forsteropsalis provided therein, Forsteropsalis pureora can easily be taken as far as couplet 6: it differs from Forsteropsalis grimmetti in lacking the latter’s flattened and ventrally white opisthosoma, from Forsteropsalis fabulosa and Forsteropsalis tumida in not having the chelicerae greatly inflated and the cheliceral fingers widely bowed, and from Forsteropsalis inconstans and Forsteropsalis nigra in not having the posterior part of the propeltidium and the mesopeltidium heavily denticulate. The only species with which Forsteropsalis pureora is likely to be confused are Forsteropsalis distincta , Forsteropsalis chiltoni , Forsteropsalis marplesi and Forsteropsalis wattsi . Forsteropsalis pureora can be distinguished from Forsteropsalis distincta by the presence of denticles in the anterior propeltidial area, whereas Forsteropsalis distincta has the prosomal dorsum unarmed but for the anterior corners. From Forsteropsalis chiltoni , Forsteropsalis marplesi and Forsteropsalis wattsi , Forsteropsalis pureora can be distinguished by the absence of a distinct pedipalpal patellar apophysis. It can also be distinguished from Forsteropsalis wattsi by the absence in the latter of denticles on the femora. Forsteropsalis chiltoni and Forsteropsalis marplesi are larger species (both have the prosoma more than 2 mm in length) with more developed denticulation at the anterior corners of the prosoma, and without any medial stripe on the opisthosoma. The latter two species also differ from Forsteropsalis pureora in genital morphology: both have the glans in ventral view narrowing anterior to the lateral bristle groups ( Taylor 2011, Figs 97, 118) while that of Forsteropsalis pureora is more constant in width.

Description.

Male: Total body length 3.73, prosoma length 1.77, prosoma width 2.83. Dorsal prosomal plate honey-brown with large white patches covering much of median propeltidium on either side of ocularium and becoming diffuse behind ocularium, postocularial area yellow-grey; anterior propeltidium with sharp denticles, remainder of dorsum unarmed but with scattered black setae; ocularium white. Mesopeltidium forming raised ridge, medially pale yellow-grey, darkening to honey-brown laterally. Ozopores on raised lateral lobes, anterior ozopore lobe with distinct white patch, remainder of lateral shelves honey-brown with smaller white patches on posterior ozopore lobe and near posterior end of shelf. Metapeltidium and dorsum of opisthosoma light purple with median white stripe and transverse rows of white spots across segments. Mouthparts white; coxae mottled honey-brown proximally, darker brown distally; genital operculum honey-brown; venter of opisthosoma light purple.

Chelicerae: Segment I 7.06, segment II 8.94. Segment I darker yellow-brown with white patches at distal end; segment II orange-brown; both segments evenly denticu late; segment II not inflated. Cheliceral fingers (Fig. 2c) long, only slightly bowed, movable finger with numerous setae close to median tooth.

Pedipalps: Femur 2.00, patella 0.98, tibia 1.21, tarsus 2.75. Coxa with numerous sturdy denticles on prolateral margin. Pedipalps long, slender, femur with dorsal and ventral rows of denticles; femur proximally honey-brown except cream-coloured heel; distal end of femur, patella and tibia white mottled with cream; tarsus cream-coloured. Patella and tibia (Fig. 2d) straight, patella with concentration of strong setae at prolateral distal end but without distinct apophysis. Microtrichia on distal two-thirds of tarsus. Tarsal claw ventrally rugose.

Legs: Leg I femur 7.03, patella 1.48, tibia 6.04; leg II femur 11.70, patella 1.74, tibia 11.64; leg III femur 7.00, patella 1.51, tibia 5.44; leg IV femur 8.32, patella 1.38, tibia 7.83. Femora with relatively few small denticles dorsally; other segments unarmed. Trochanters honey-brown with white distal retrolateral spot on each trochanter. Femora proximally dull medium yellow, distal ends of femora to tibiae honey-brown mottled with white spots; tibiae lighter orange-brown banded with dull yellow. Tibia I with two pseudosegments; tibia II with ten pseudosegments; tibia IV with three pseudosegments.

Penis (Figs 2 e–f): Glans relatively long, sides parabolic in ventral view; triangular in lateral view. Bristle groups of medium length. Tendon long.

Comments.

Another feature of Forsteropsalis pureora that may deserve further investigation is the unusually high number of pseudosegments in the leg tibiae. Not only does the holotype have a higher number of pseudosegments in tibia II than recorded for any other Forsteropsalis species, even the particularly large species Forsteropsalis fabulosa and Forsteropsalis tumida , it represents the first recorded instance in this genus of pseudosegmentation in tibia I. At our present level of knowledge, this cannot be considered a reliable distinguishing character for the species as tibial pseudosegment number has been found in other species to vary between individuals. However, pseudosegment number has been suggested to distinguish Forsteropsalis chiltoni and Forsteropsalis marplesi in which, so far as is known, males of each species have varying but non-overlapping ranges of pseudosegment number for tibia II ( Taylor 2011). This may reflect differences in leg proportions between the two species: despite Forsteropsalis chiltoni having a generally larger body size than Forsteropsalis marplesi (average prosomal length 3.1 mm in two specimens of Forsteropsalis chiltoni vs 2.5 mm in four specimens of Forsteropsalis marplesi ), Forsteropsalis marplesi specimens may have relatively longer legs (average length of tibia II 9.8 mm in Forsteropsalis chiltoni vs 11.8 mm in Forsteropsalis marplesi ) (unpublished personal observations). Like examined specimens of Forsteropsalis marplesi , the holotype of Forsteropsalis pureora has relatively long legs compared to body size. However, the significance of these observations remains open to question. Previous morphometric studies of other Opiliones have found leg measurements to be useful in distinguishing taxa among Goniosomatinae (Laniatores; Gnaspini 1999) but not Leiobunum ( McGhee 1977). A detailed morphometric study to establish the reliability and/or significance of such measurements in distinguishing taxa will require a much larger sample of specimens than currently available for most Forsteropsalis species.