Taracus Simon 1879

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: 12-14

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Taracus Simon 1879


Genus Taracus Simon 1879  

Taracus Simon 1879:74   . Schönhofer 2013:21 (complete list of species and references) Type species: Taracus packardi Simon 1879   , by monotypy.

Diagnosis. Species of Taracus   and the new genus Oskoron   can readily be distinguished from all other ischyropsalidoids by the presence of a single metapeltidial sensory cone. The abdomen is often unsclerotized except for small plaques, but ranges to scutum parvum (in which the first five abdominal terga are fused into a scutum that remains separate from the carapace) in the males of some species. Unlike sabaconids, surface-dwelling Hesperonemastoma   are heavily sclerotized, entirely black in color (the color of the two troglobiotic Hesperonemastoma   species range from pale brown to transparent white [ Shear 2010b]), lack sensory cones, and the metapeltidium, abdominal scutum and carapace are fused into a single dorsal shield. In Sabacon   , relatively softbodied like Taracus   , the palpal tibia is inflated and bears a glabrous area distally, against which the tarsus reflexes; in Taracus   the articles are not conspicuously inflated and the glabrous area on the tibia is absent. Sabacon   species all have two sensory cones and at most show scutum parvum, but most European and Asian Sabacon   species have poorly sclerotized abdomens. For other genera of the superfamily, Ischyropsalis   species have multiple sensory cones, while species of Acuclavella   and Ceratolasma   , like Sabacon   species, have two. Crosybcus, like Hesperonemastoma   , lacks sensory cones. These latter four genera show scutum parvum or completum, with heavy sclerotization.

From the closely related Oskoron   , Taracus   can be separated by the chelicerae longer than twice the body length, the lack of modified palpal patellae in males, and by the distinctive seta-tipped tubercles that cover the abdomen and ocularium of Oskoron   species. In Taracus   , the endites of the second coxae are strongly reduced and separated from the coxae (a synapomorphy for Taracus   ), but in Oskoron   they are inserted in unsclerotized recesses in the coxae.

Description. Body length from 4–10 mm. Carapace usually black or dark chestnut brown in adults, broadest behind, with long midline sulcus extending from between chelicerae to ocularium and in some cases marked as median line over ocularium; in lightly pigmented specimens, two prominent slit sense-organs just anterior and lateral to ocularium on each side; carapace often poorly sclerotized posteriolaterally, smooth to finely shagreened texture. Ozopores small, not concealed, dorsolateral, over first leg coxae. Ocularium low, at least as wide as long; smoothly rounded; smooth or with few small setae above eyes. Eyes large or reduced. Metapeltidium free, sclerotized or not, may appear to be partially coalesced with carapace, sometimes marked only by transverse row of small setae, or lacking setae entirely; sensory cone single, median, may be flanked by smaller acute tubercles, set into unsclerotized embayment in posterior margin of carapace, or, if metapeltidium sclerotized, in prominent, white socket. Abdomen soft, white, set with rows or irregular groups of small setae, or with scattered sclerotized (orange to brown) raised plaques bearing larger, robust, acute setae, these patches sometimes coalesced in midline to form small segmental sclerites (partial scutum laminatum; Figs. 8, 9 View FIGURES 4 – 15 ), or with true scutum laminatum ( T. gertschi   , Fig. 41 View FIGURES 37 – 45 ); males of most species with scutum parvum, but lateral boundaries of scutum poorly defined ( Figs. 22, 23 View FIGURES 16 – 27 ), plaques may remain prominent within scutum.

Labral sclerite large, pentagonal, with three prominent projections. Labium small, setose. Thoracic sternum absent in males, present in females of some species as two small tubercles bearing few setae. Endites of legs 3 and 4 indistinguishably fused to coxae, free on second coxae, distant from second coxae as small, elongate, setose lobes directed ventrally. Genital operculum with sclerotized distal rim, may be sexually dimorphic (males: evenly rounded; females: apically triangular) or not. Abdominal sternites well-sclerotized to not at all sclerotized, with small setae scattered or sparsely arranged in rows.

Chelicerae black, robust, elongate, ranging from 1.5 to as much as 3 times body length; basal articles with mediobasal opposed tubercles, set throughout length with seta-bearing tubercles of various sizes, usually largest near basoventral section of articles, smaller distally. Second articles generally more robust, longer; seta-tipped tubercles of these may be at least partially in regular rows, numerous. Fixed and movable fingers turned sharply mesad at approximate 125° angle to long axis of second article; fingers with diaphanous cleaning combs.

Palpi long, thin; trochanter with few to several ventral seta-tipped tubercles, femora and patellae with moderately dense coat of fine setae; tibiae and tarsi densely set with plumose glandular hairs of Wolff et al. (2016) type 6 ( Fig. 55 View FIGURES 53 – 57 ). Tibiae lack glabrous area opposite tarsi. Tarsi short, not strongly reflexed, without claw or with small, barely detectable vestigial claw. Palpi of males may be shorter than in females, but without modification of patellae.

Legs in order of length: 2,4,3,1 or 2,4,1,3 or 2, 4, 1 = 3. Femora with autospasy suture near base; may be obscure or absent. Tibiae without false articulations, metatarsi with or without false articulations, tarsi multiarticulate, bearing single untoothed claw, vestiture of fine setae, appressed trichomes ( Fig. 56 View FIGURES 53 – 57 )

Ovipositor typical of ischyropsalidoids, short, unsegmented, without special apical sensilla, distally divided into two setose lobes. Penis relatively long, straight, distally tapered, muscles extending two-thirds or more length of shaft; glans distinct, swollen, sclerotized, evidently not movable, tapering into short aculeus, without macrosetae, set with small, short setae around base of aculeus, sometimes with short rows of lateral setae subtending glans.

Included species: Taracus packardi Simon, 1879   (= T. nigripes Goodnight & Goodnight 1943   ), T. pallipes Banks 1894   , T. silvestrii Roewer 1929   , T. gertschi Goodnight & Goodnight 1942   , and the following new species: carmanah   , marchingtoni   , fluvipileus   , taylori   , spesavius   , timpanogos   , audisioae   and ubicki   ; Taracus spinosus Banks 1894   (= T. malkini Goodnight & Goodnight 1945   ) is transferred to the new genus Oskoron   .

Distribution. Rocky Mountains of Colorado, southernmost Wyoming and northern New Mexico; isolated populations in caves in Utah and eastern Nevada; southeastern British Columbia and adjacent Alberta, Montana and Idaho; Vancouver Island and southwestern British Columbia south to northern California in the Coast Ranges and Cascade Mountains; San Francisco Bay area, Sierra Nevada of California; lava tubes in central Oregon; Vladivostok region of Siberia. In a preliminary work Shear (1986) also mentioned and mapped a record from northeastern Arizona; while such an occurrence is still plausible, we were not able to verify this from specimens examined for this study.

Etymology. Taracus   (or Taharqa, reigned 690-664 bce) was an Egyptian king, a successor to Sabacon   (or Shabako, reigned 713-698 bce). Christian mythology also recognizes a St. Tharacus, but Simon (1879) based the name on the Egyptian king, presumably to emphasize a perceived relationship to Sabacon   . Gender of the name is masculine.












Taracus Simon 1879

Shear, William A. & Warfel, Joseph G. 2016


Schonhofer 2013: 21
Simon 1879: 74