Arcanobisium, Zaragoza, Juan A., 2010

Zaragoza, Juan A., 2010, Arcanobisium, a remarkable new genus, representing a new subfamily with a relictual distribution from eastern Spain (Arachnida: Pseudoscorpiones: Syarinidae), Zootaxa 2491, pp. 41-60 : 43-44

Arcanobisium gen. nov.

Type species. Arcanobisium comasi sp. nov.

Etymology. From arcanus: arcane (Latin) meaning hidden, secret or mysterious.

Diagnosis. As for the subfamily (monotypic). The following characters may be of generic importance. Carapace with epistome; eyes absent. Trichobothrium ib located in basal half of hand; trichobothria isb -esb -eb situated in distal portion of hand; trichobothrium eb slightly distad of esb; ist situated in basal half of finger and far from est. Femur of leg IV slightly longer than patella; subterminal tarsal seta apically denticulate.

Description. Pleural membrane striate dorsally and ventrally and weakly granulated in-between. Carapace considerably longer than broad, with a small, rounded epistome, without traces of eyes. Apex of pedipalpal coxa triangular, with two setae, anterolateral process of coxa I short and rounded. Tergites and sternites up to segment IX wide, tergites and sternites X–XI narrow and inconspicuous. Chelicera with 5 setae on hand, galea simple, rallum with 5 blades unilaterally serrate on anterior face. Pedipalps granulate, except chela apparently smooth; chelal hand and fixed finger with irregular outline, movable finger markedly curved; with 8 trichobothria on fixed finger, ib on dorsum of hand in the basal half, isb -esb -eb on the antiaxial face of hand, in distal region, ist isolated on the basal portion of the fixed finger, est close to et, and it at the tip of the finger distal to et; 4 trichobothria on movable finger, t lanceolate, st close to t, both slightly distal of the finger half, sb about halfway between b and st; venom duct only present in fixed finger, short and with expanded nodus ramosus; teeth contiguous on both fingers and approximately of same size. Male genital atrium with 3 internal glandular setae on each side. Femora of legs I and II without basi-dorsal mound, junction of femurpatella on legs III and IV perpendicular, femur slightly longer than the patella, subterminal tarsal seta of all legs dentate.

Remarks. Compared with other syarinid genera, Arcanobisium resembles Chitrellina Muchmore, 1996 , known only from a cave in Arizona ( U.S.A.), in having the galea simple, trichobothrium ib in the basal half of the chelal hand, and the carapace much longer than broad, with an epistome. These genera differ in the position of the trichobothria ( Chitrellina with et apical and it far basal) and the form of the coxae of leg IV (posterior prolongations present in Chitrellina ). In addition to the subfamilial characteristics, Arcanobisium differs from the Mediterranean-Macaronesian genera Microcreagrina and Microcreagrella by the lanceolate trichobothrium t, the apical position of it and the lack of a row of chelal feather-shaped setae. Microcreagrella further differs from the new genus by the basal position of eb. Arcanobisium differs from Hadoblothrus by the shape of the chelal hand and patella, as well as by the position of trichobothrium ist, which is distal to est in Hadoblothrus .

The granulate or striate condition of the pleural membrane is not uniform in the Syarinidae and cannot be used to distinguish this family from Neobisiidae ( Muchmore 1982) because some genera show a combination of both conditions, e.g. Alocobisium Beier, 1952 , Ideobisium Balzan, 1892 and Arcanobisium gen. nov. ( Mahnert 1979; Muchmore 1982; this study).

The femur of leg IV is longer than the patella in Arcanobisium and distinctly shorter than the patella in the other syarinid genera, with the exception of Hadoblothrus .

Muchmore (1996) supported the description of a new genus based on an unique individual when its characteristics makes it “so different from other pseudoscorpions that it cannot be placed in any previously described genus”. He also recognized the frequent difficulty of obtaining specimens from caves. The holotype of Arcanobisium comasi was collected nearly 30 years ago in the cave Avenc d’en Serenge, Castellón, where pseudoscorpions have been collected regularly during the last 40 years, and only one specimen of the new species has been found. The vial with the sample also contained two specimens of a species of Troglobisium . Recent efforts of researchers of the Museu Valencià d’Història Natural to collect more specimens of the new genus were unsuccessful.