Taracus spesavius Shear

Shear, William A. & Warfel, Joseph G., 2016, The harvestman genus Taracus Simon 1879, and the new genus Oskoron (Opiliones: Ischyropsalidoidea: Taracidae), Zootaxa 4180 (1), pp. 1-71: 45-46

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Taracus spesavius Shear

new species

Taracus spesavius Shear   , new species

Figs. 89–93 View FIGURES 89 – 93 , Map 6

Types. Male holotype from Lost Hope Cave , Ruby Mtns., 6.4 km WSW of Ruby Lake, Elko Co., Nevada, collected August 2002 by R. Aalbu ( CAS).  

Diagnosis. The single available specimen of this species differs from T. taylori   in a number of respects; the eyes are of normal size and pigmented, the legs are significantly longer than in that species, the chelicerae are smaller, more slender and less spiny, and there are fewer abdominal setae. As mentioned under T. taylori   above, the hypothesis that this single individual represents a distinct species should be tested using genetic data from fresh collections.

Etymology. The species epithet is a noun in apposition, “lost (or wandering) hope,” suggested by Rod Crawford.

Description. Male from Lost Hope Cave. Total length, 5.1 mm. Carapace medium chestnut brown, more lightly sclerotized laterally, with distinct oblique lines lateral to ocularium; central region strongly domed; midline sulcus closed, reaching anterior margin of ocularium. Ocularium as wide as long, rounded, higher behind, with few small setae; eyes pigmented, of normal size for epigean species. Metapelitidium lightly sclerotized, with short row of small setae; sensory cone brown, acute, inclined forward over posterior part of ocularium. Abomen soft, white, unsclerotized, set with scattered, small, black setae; setae not on sclerotized plaques or tubercles ( Figs. 92, 93 View FIGURES 89 – 93 ). Ventrally, coxae brown to tan, with few dark brown spots. Palpal and first leg coxae brown, with stout setae on distinct tubercles, second to fourth leg coxae pale tan to almost white, with strong, black setae not on tubercles. Five or six setae in two groups on lightly sclerotized patches mark presumed position of thoracic sternum. Second coxal endites long, narrow, separate from coxae. Genital operculum apically rounded, heavily setose, pale tan with large, dark brown spots. Venter of abdomen with densely scattered setae, abdominal sterna not discernable.

Chelicerae 9.73 mm long, slender, black. Basal article 4.30 mm long, 0.39 mm wide (L/W = 11.03); second article 5.43 mm long, 0.48 mm wide (L/W = 11.31). Basal article with small, well-spaced seta-tipped tubercles extending three-quarters of length, dorsal tubercles much smaller; second article with quite low, rounded setatipped tubercles ranged in about five irregular rows, tubercles more widely spaced distally. Fixed and movable fingers with paired, articulating triangular teeth, narrow, acute tips of fingers cross each other at rest.

Palpi ( Fig. 89 View FIGURES 89 – 93 ) with femora dark brown, distally from patella fading to white; total length 13.47 mm, typical for genus; trochanter with prominent scattered seta-tipped tubercles. Lengths of articles as given in Table 15. Legs long, thin; first leg femur light brown, becoming lighter distally, other legs yellowish tan, bases of femora with few brown spots.. Autospasy suture of femur distinct on all legs. Tibiae without false articulations, metatarsi of legs 1 with about four poorly indicated false articulations; leg 2 with about 15 very faint false articulations. Total lengths in mm of legs 1–4: 19.71, 35.57, 19.68, 25.46. Measurements of leg articles given in Table 15.

Penis ( Figs. 90, 91 View FIGURES 89 – 93 ) 3.25 mm long, 0.27 mm wide (L/W = 12.04), sides of shaft straight, tapering gradually to slightly twisted, short aculeus; glans not set off by suture; aculeus subtended by crown of few small, acute setae; shaft with numerous smaller scattered setae on either side below glans.

Distribution. Known only from Lost Hope Cave, about 6.4 km WSW of Ruby Lake, Elko Co., Nevada. We do not further locate the cave itself because of conservation concerns.

Notes. Lost Hope Cave is situated at about 7600’ asl in the Ruby Mountains; while at this altitude and latitude, pine-juniper woodland would be the expected vegetation, in the Ruby Mountains sagebrush scrub extends to 8000’ or slightly above, definitely not good habitat for Taracus   . Observation of the area of the cave via Google Earth shows only scattered trees, sparse clumps of sagebrush, and virtually no ground cover. It is likely that T. spesavius   is limited to caves, although populations might exist in riparian habitats. While there may be the possibility of populations at higher elevations, even the crest of the Ruby Mountains (over 10,000’ asl) has little or none of the dense forest that seems to be required by Taracus   .

The single individual available, unlike the males of T. taylori   , has pigmented eyes that approach normal size. However, varying degrees of troglomorphy can occur in opiliones   populations that are (by genetic measures) the same species (Dekarabetian et al. 2010).


California Academy of Sciences