Taracus taylori 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 : 42-45

Taracus taylori Shear , new species

Figs. 77–88 , Map 6

Types. Male holotype, male and four female paratypes from Snake Canyon Cave, 9100’ asl, Schell Creek Range , 13 km east-northeast of McGill , in Humboldt-Toiyabe National Forest , White Pine County, Nevada, collected 8 June 2012 by S. J. Taylor, T. Gilleland and L. Santisteban, and on 31 October 2011 by J. Knight, A. Smith and B. Szukalski; these specimens deposited in the Illinois Natural History Survey. Female paratype from the same locality, but collected 28 October 1967 by an unknown person; deposited in CAS .

Diagnosis. Only this species and T. spesavius , n. sp., are known from Nevada; the latter species occurs to the north in the Ruby Mountains. The two are very close, but spesavius does not have reduced eyes. The two species also differ in leg length, though the body length is about the same; taylori has shorter legs. The chelicerae of T. taylori are larger, thicker, and more spiny than in T. spesavius , and the abdomen is more setose (though setation is quite sparse in both species). Given the isolation of the two mountain ranges by inhospitable sagebrush desert, we hypothesize that the populations are reproductively isolated and therefore constitute species. Future genetic studies can test this hypothesis.

Etymology. The species epithet honors biospeleologist Steven Taylor of the Illinois Natural History Survey, whose collecting in Great Basin caves has helped to reveal a surprisingly extensive and complex fauna.

Description. Male from Snake Canyon Cave. Total length, 5.4 mm. Carapace dark chestnut brown to black, more lightly sclerotized laterally, marked irregularly with lighter areas; central region strongly domed; midline sulcus closed, does not reach anterior margin of ocularium. Ocularium as wide as long, rounded, higher behind, with few small setae; eyes reduced to about one-half diameter of those of epigean species. Metapelitidium lightly sclerotized, with short row of small setae; sensory cone long, brown, acute ( Figs. 82, 83 ), inclined forward, then recurved, resting in shallow depression in posterior surface of ocularum. Abomen soft, white, unsclerotized, set with scattered, small, black setae; setae not on sclerotized plaques or tubercles, very lightly sclerotized midline patches on first two areas ( Figs. 84, 85 ). Ventrally, coxae white to tan, irregularly mottled dark brown. Palpal and first leg coxae brown, with stout setae on distinct tubercles, second to fourth leg coxae pale tan, 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 setae in irregular rows on lightly sclerotized transverse bands marking positions indistinct abdominal sternites.

Chelicerae ( Fig. 88 ) 11.82 mm long, slender, black. Basal article 5.20 mm long, 0.44 mm wide (L/W = 11.82); second article 6.24 mm long, 0.68 mm wide (L/W = 9.18). Basal article with prominent, acute seta-tipped tubercles extending three-quarters of length, dorsal tubercles much smaller; second article with relatively 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. 78 ) dark brown, total length 13.48 mm, typical for genus; trochanter with prominent scattered setatipped tubercles. Lengths of articles as given in Table 13 . Legs long, thin; first leg brown, becoming lighter distally, other legs yellowish tan without markings.. Autospasy suture of femur indistinct on legs 1, 3. Tibiae without false articulations, metatarsi of legs 1, 3, 4 with about 15–17 false articulations; leg 2 with numerous very faint false articulations. Total lengths in mm of legs 1–4: 17.28, 27.94. 17.04, 21.95. Measurements of leg articles given in Table 13 .

Penis ( Figs. 79–81 ) 2.54 mm long, 0.22 mm wide (L/W = 11.54), 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 few similar scattered setae on either side below glans.

Female from Snake Canyon Cave: As for the male holotype, except as follows. Total length, 5.63 mm ( Figs. 82, 83 ). Cheliceral ( Figs. 86–87 ) basal article 5.90 mm long, 0.53 mm wide (L/W = 11.13); second article 7.05 mm long, 0.84 mm wide (L/W = 8.39). Total length of palpus ( Fig. 77 ), 14.12 mm. Depression in posterior margin of ocularium that receives sensory cone deeper than in male. Metatarsal false articulations not detectable in metatarsi 2 (podomere very thin). Total lengths in mm of legs 1–4: 17.09, 27.52, 16.02, 21.88; lengths of leg and palpal articles as given in Table 14 . Ovipositor typical.

Distribution. Known only from Snake Canyon Cave, White Pine Co., Nevada. Snake Canyon is located at 39°26’54”N, 114°39’00”W, on the west slopes of the Schell Creek Range, near McGill, Nevada. We do not further locate the cave itself because of conservation concerns.

MAP 5. Parts of the states of Idaho, Montana, Oregon and Washington and the provinces of British Columbia and Alberta. Filled circles, localities for Taracus gertschi Goodnight & Goodnight.

MAP 6. Parts of Nevada and Utah . Filled circle, type locality of Tarcus taylori , n. sp.; filled triangle, type locality of T. spesavius , n. sp.; filled squares, localities for T. timpanogos , n. sp.

Notes. The following notes are courtesy of Steve Taylor (pers. comm. 2013). The peak above Snake Canyon reaches 11,073’ asl, but despite the altitude the region is quite dry; larger pines are found only along the canyon floors. The immediate surroundings of the cave are rocky and vegetated by low oak, Mormon tea and sagebrush; there is little or no litter cover. In general the habitat does not appear favorable for Taracus outside the cave or higher on the mountain. The cave supports a population of Neotoma packrats with their middens and feces providing habitat for phorid and sciariid flies as well as fleas; these insects could be prey for Taracus taylori .

We would hypothesize, given the habitat (scanned via Google Earth), that there are not likely to be epigean Taracus populations in the Schell Creek Range. The long legs, reduced eyes and weak abdominal sclerotization of individuals of T. taylori speak to moderate troglobiosis, perhaps developed since the last pluvial period ended some 15,000 years ago and increasing drought extinguished surface populations of Taracus . It remains to be seen if other caves in the Schell Creek Range and indeed in other Great Basin inselberg ranges support Taracus populations.

Figures

FIGURES 77 – 88. Taracus taylori. Fig. 77, female palpus. Fig. 78, male palpus. Figs. 79 – 80, penis. Fig. 81, glans penis. Fig. 82, female, dorsal view. Fig. 83, female, lateral view. Fig. 83, male, dorsal view. Fig. 84, male, lateral view. Fig. 86, female chelicerae, lateral view. Fig. 87, female chelicera, second article, frontal view. Fig. 88, male chelicerae, lateral view.

Tables

TABLE 13. Lengths in mm of palpal and leg articles of male Taracus taylori.

	Femur	Patella	Tibia	Metatarsus	Tarsus
Palpus	5.67	2.78	3.81	-	1.22
Leg 1	4.52	1.10	2.52	5.71	3.43
Leg 2	6.09	1.29	4.90	9.71	5.95
Leg 3	3.95	1.09	2.76	5.67	3.57
Leg 4	5.19	1.19	3.57	7.38	4.62

TABLE 14. Lengths in mm of palpal and leg articles of female Taracus taylori.

	Femur	Patella	Tibia	Metatarsus	Tarsus
Palpus	5.80	3.05	3.97	-	1.30
Leg 1	4.60	1.18	2.47	5.60	3.24
Leg 2	6.76	1.35	5.06	9.06	5.29
Leg 3	3.13	1.12	2.65	5.30	3.82
Leg 4	5.12	1.29	3.53	7.35	4.59