ARCANOBISIINAE

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

ARCANOBISIINAE new subfamily

Type genus. Arcanobisium gen. nov.

Diagnosis. Syarinidae with opisthosoma ovate; male sternite IV without cribrate areas or modified gland openings; stigmata III with only one microseta, IV without microsetae; segment XI divided into a separate tergite and sternite, tergites and sternites X–XI extremely reduced in size, tergite XI without setae, sternite XI divided into two small plates. Triangular apex of pedipalpal coxa bearing only two setae. Pedipalpal chela with irregular outline; venom duct present only in fixed finger, short and with nodus ramosus expanded; trichobothrium t lanceolate, and bent backward; trichobothrium ib on dorsum of hand; trichobothrium it at tip of finger far distad of et. Junction between femur and patella of legs III and IV perpendicular.

The new subfamily shares with the Ideobisiinae the triangular apex of pedipalpal coxa, the presence of a smooth cheliceral galea and the absence of glands in male sternite VI, but is distinguishable from it and the other syarinid subfamilies by the ovate shape of the opisthosoma, reduced size of abdominal segments X–XI, reduced chaetotaxy of segment XI, the position of trichobothrium it at tip of finger and the reduced stigmatic chaetotaxy.

Remarks. The posteriorly reduced opisthosoma seems also unique among the Syarinidae , the opisthosoma in other genera is described as being more or less slender and elongated, even almost vermiform.

The division of segment XI into a separate tergite and sternite is also a particular characteristic among the Syarinidae . Harvey (1992: character 101) considered this state to be plesiomorphic within the order, but Judson (2000) argued that it was apomorphic.

The tergal and sternal plates are well sclerotized and depigmented, decreasing in width from the anterior to the posterior segments and highly reduced in segments X–XI. The division of sternite XI into two small plates is interpreted as a progressive reduction of the sternite, since careful examination has not revealed retraction under the anterior sternite.

The creation of a new subfamily of Syarinidae for is justified by the exceptional features of Arcanobisium . These include the reduction of segments X–XI, reduced stigmatic chaetotaxy and segment XI divided into a tergite and sternite.