Spinonychiurus Weiner, 1996

Pomorski, Romuald J. & Kapruś, Igor J., 2015, Revision of the genus Spinonychiurus Weiner 1996 (Collembola: Onychiuridae) with description of five new species, Zootaxa 3914 (2), pp. 101-121 : 102

Spinonychiurus Weiner, 1996

Type species: Onychiurus edinensis Bagnall, 1935: 117 .

Diagnosis. Abdominal sternum III divided into two subsegments, each with an own set of chaetae. Dorsal side of body with dorsoaxial and lateral pseudocelli. Posterior cephalic pseudocelli present. Furca reduced to small area of fine granulation in the centre of abdominal sternum IV and three rows of manubrial chaetae (2+2 small chaetae arranged in two manubrial rows behind depression). Antennal III sensory organ consisting of 5 guard chaetae, 5 papillae, 2 sensory rods and 2 sensory clubs more or less bent with surface from smooth to granulated, always with longitudinal ribs. Postantennal organ with compound, granulated vesicles. Labial palp A or AB type. Head of maxilla short with unmodified lamellae and typical ungulus. Dorsal chaetae usually well differentiated into apically rounded macro- and mesochaetae, and apically pointed microchaetae. Anal spines present or absent. If anal spines present, abdominal tergum VI with 1+1 prespinal chaetae. Sensory chaetae on antennae well marked. Head with d0 chaeta absent. Tibiotarsi with 7, 9 or 11 chaetae in distal whorl (A+T). Male ventral organ (if present) located on ventral tube and rarely also on genital plate.

Discussion. The structure of furcal field and relatively distinct sensilla on the antennae and body place Spinonychiurus within the tribe Thalassaphorurini ( Pomorski 1998). The unique character of the genus is the division of abdominal sternum III on two distinct subsegments, each covered by chaetae. This character has never been found within the tribe Thalassaphorurini and even in the subfamily Onychiurinae before. Spinonychiurus shares the absence of d0 chaeta on the head and granulated vesicles in its postantennal organ with Detriturus Pomorski, 1998 and Sensillonychiurus Pomorski & Sveenkova, 2006 . According to Babenko et al. (2011), this genus can be distinguished from Sensillonychiurus by the number of guard chaetae in antennal III sensory organ (5 in Spinonychiurus , 3–4 in Sensillonychiurus ) and from Detriturus by the separation of V–VI abdominal segments (fused in Detriturus ), besides having subdivided of abdominal sternum III.