Taracus aspenae Shear, 2018, n. sp.
Creators: name: William A Shear
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Opiliones
Taracidae
Taracus
Taracus aspenae

description: Taracus aspenae n. sp.
Figs. 1 –13.
Types: Male holotype, two male and eight female paratypes from Catherine Creek Ice Cave (N45° 08' 29.2" W117° 43' 23.4"), 3392 ft [1034 m] asl, 22 mi [35 km] SE of Le Grande, Union Co., Oregon, USA, collected 30 August 2017 by Neil Marchington, deposited in the California Academy of Sciences, San Francisco, California, USA.
Etymology: The species epithet honors Aspen Marchington, who preserved and prepared the specimens.
Diagnosis: Taracus aspenae is potentially sympatric with T. gertschi, known from surface collections in the adjoining counties of Grant, Wallowa and Baker (Shear & Warfel 2016). The new species differs from T. gertschi in having longer, thinner, spinier chelicerae and longer palps and legs in comparison to body length. The penis of male T. aspenae, while similar in form, is longer and narrower than that of T. gertschi. Females of T. aspenae, like those of T. gertschi, show scutum laminatum, but more poorly developed with the individual plaques often bilaterally separate; males of T. aspenae show scutum laminatum also, while T. gertschi males have scutum parvum. Taracus aspenae also resembles T. pallipes (Banks, 1894), which occurs considerably to the west in Oregon, but in which the penis is quite different (see Figs. 18, 19 in Shear & Warfel 2016) and in which the males also show scutum parvum even more strongly than in T. gertschi.
Description: Male holotype. Total length, 5.0 mm. Carapace (Figs. 1, 3) uniformly dark chestnut brown, lateral and posterior margins not well-defined; strongly domed; midline sulcus narrow, appearing closed, extending from anterior margin of carapace to ocularium. Ocularium as wide as long, rounded, without prominent setae; eyes somewhat reduced, appearing dark gray. Metapelitidium entirely unsclerotized, long, without setae; sensory cone with white, membranous base, distal sclerotized part brown, acute, adjacent to or set in small recess in posterior margin of carapace. Abdomen (Fig. 1) soft, white base color faintly shaded with pale purplish gray pigment in band behind carapace (metapeltidium), also in central area; with scutum laminatum, first four abdominal tergites with large central plaques, laterally set with small plaques that become smaller laterally, these plaques each with a small seta; fourth large central plaque partly divided in midline. Sides of abdomen with scattered, small, black setae. Ventrally, coxae pale yellowish tan, spotted, fourth coxae with considerable dark spotting. Palpal coxae with numerous stout setae on distinct tubercles, leg coxae with few strong, black setae, not on tubercles. No indication of thoracic sternum. Genital operculum apically rounded, nearly asetose, pale yellowish tan with dark spotting especially posteriorly, with unsclerotized distal lip. Abdominal sternites unsclerotized, brushed darker posteriorly, with few scattered black setae.
Chelicerae (Figs. 3, 9, 10) 11.20 mm long, black. Basal article 5.58 mm long, 0.50 mm wide (L/W = 11.16); second article 5.62 mm long, 0.96 mm wide (L/W = 5.85). Basal article with prominent mediobasal knob, with numerous seta-tipped tubercles extending entire length, ventral row of prominent, curved tubercles extends entire length of article, fewer tubercles dorsally; second article with more prominent, rounded seta-tipped tubercles ranged in about four to six irregular rows, tubercles more widely spaced and smaller distally. Fixed and movable fingers with paired, articulating triangular teeth, narrow, acute tips of fingers cross each other at rest.
Palpus (Fig. 5) total length 12.59 mm, brown, trochanters contrasting dark brown, other podomeres uniform in color, unspotted. Palpi relatively slender; trochanters with five or more prominent, seta-tipped tubercles, femora with regularly spaced slender setae, not set on tubercles. Patellae not swollen. Lengths of articles as given in Table 1. Legs long, thin; light brown, unspotted but for few scattered spots on femora. Tibiae without false articulations, metatarsal false articulations 5, 12, 3, 5 respectively; tarsal articles 6, 21, 13, 14 respectively. Total lengths in mm of legs 1–4: 15.93, 25.44, 16.27, 20.08. Measurements of leg articles given in Table 1.
Penis (Figs. 11 –13) 2.16 mm long, 0.30 mm wide (L/W = 7.2), sides of shaft straight; glans not swollen, gradually tapering to twisted, slightly sinuate aculeus; distal glans with subtending sparse crown of setae; shaft with few scattered small setae distally, these set in deep sockets; shaft with many slit sense organs.
Female paratype: Total length, 7.5 mm. Carapace (Figs. 2, 4) dark chestnut brown to blackish, paired slightly lighter areas with darker diagonal streaks behind ocularium. Metapeltidium lightly sclerotized only in central region; single row of small setae on either side of sensory cone. Abdomen (Fig. 2) heavily shaded purplish brown, with scutum laminatum as small central plaques of which the first two are unitary, the others paired, between these, few irregularly arranged smaller plaques. Genital operculum with unsclerotized lip, sclerotized proximal articulations.
Chelicerae (Figs. 4, 7, 8) 12.38 mm long, basal article 6.52 mm long, 0.48 mm wide (L/W = 13.58); second article 5.86 mm long, 0.76 mm wide (L/W = 7.71); chelicerae with fewer, less prominent tubercles than male. Total length of palpus (Fig. 6), 11.66 mm; podomere lengths as in Table 2. Total lengths in mm of legs 1–4: 15.43, 24.87, 15.75, 21.51; lengths of leg articles as given in Table 2. Metatarsal false articulations 5, 14, 2, 5, tarsal articles 6, 21, 13, 14. Legs sometimes heavily spotted. Ovipositor typical. Other characters as in male.
Notes: The type locality is a small fissure or fault cave with about 50 feet [15 m] of passageway. It is located at the base of a talus slope with many fractures and small openings. Despite the name, the cave does not have permanent ice and none was seen in the course of two visits (both in August) but a “very cold wind” continually blows from the cave. The slope is only few meters (and across a road) from Catherine Creek, located in a transition zone between the riparian habitat and the semi-arid pine (Pinus ponderosus Douglas ex Lawson, 1836) woodland. The cave is rich in organic material derived from wood rat middens. Harvestmen (Leiobunum sp.), collembolans and Pacific tree frogs (Pseudacris regila) were observed in the cave (Neil Marchington, pers. comm. 2017). The surrounding surface habitat, observed through LandSat photographs, does not appear optimum for a Taracus species, except possibly in the riparian zone of Catherine Creek. However, talus slopes and fissure caves offer abundant and complex three-dimensional space for colonization by small arthropods, which, like Taracus species, prefer cool, damp habitats. If T. aspenae does have surface populations, the collection of adults in August suggests that the species matures in the summer months, like T. gertschi, in contrast with the winter-maturing T. pallipes. Reduced abdominal sclerotization, slightly smaller and less well-pigmented eyes and more elongated appendages than in related species suggests some degree of subterranean adaptation in T. aspenae. Some species of Taracus are clearly cave-limited by much more profound adaptations to conditions underground, but for others, such as T. timpanogos Shear, 2016 or T. silvestrii Roewer, 1929 such adaptations are either slight or indiscernible. However, surface populations, if they exist, remain undiscovered, very likely due to more assiduous collection in caves rather than in the surrounding environments.
description: Published as part of William A Shear, 2018, Taracus aspenae, n. sp. (Opiliones: Taracidae) a new long-jawed harvestman from a cave in northeastern Oregon, U. S. A., pp. 524-530 in Zootaxa 4413 (3) on pages 525-529, DOI: 10.11646/zootaxa.4413.3.6, http://zenodo.org/record/1228018