Aggressopygus armatus Potapov & Babenko 2014, sp. nov.

Figures 4B, 6

Holotype: female of unclear age, Kazakhstan, Alma-Ata area, ca 35 km SE Issyk, Chin-Turgenskoye Canyon, ~ N 43.12º Е 77.45º, ~ 2100 m alt., litter on canyon bottom, 21.08.1991. leg. M. Potapov. Two paratypes from the same locality. Deposited in MSPU.

Length of mature specimens unknown (0.53 mm in holotype). Without pigmentation and ocelli. Cuticle with ‘smooth’ granulation. PAO broad, slightly constricted, longer than width of Ant.I and more than twice as long as inner unguis length (Figure 6E). Maxillary outer lobe and maxillary palp as common for genus. Labral formula as 4/ 5,5,4, setae of two distal rows slightly thickened (Figure 6F). Labium with 5 papillae and 16 guard setae. Hypostomal papilla unmodified. Three proximal and 4 basomedian setae. Detailed morphology of maxillary head not studied, maxillary teeth less developed and Lam.1 longer than in A. sibiricus sp. nov. Ventral side of head with 3 + 3 setae. Ant.1 with 2 ventral sensilla (s) and 2 small basal microsensilla (bms), Ant.2 with 3 bms and 1 laterodistal s, Ant.3 with 1 bms and with 5 or 6 distal s (including 1 or 2 lateral), without additional sensilla. Organite of Ant.4 stick-like.

Common setae of body smooth. Axial chaetotaxy for Th.III–Abd.III as 6/3,3,3. Tergal sensilla well differentiated. Sensillary formula as 4,3/2,2,2,3,5 (s), microsensilla (ms) as 1,0/0,0,1 (Figure 4B). Medial sensilla on Th.II–III situated in front of p-row, on Abd.I–IV in posterior position. Medial sensilla on Th.III–Abd.I short. Abd.V with 5 sensilla arranged with 3 dorsal middle-sized (al, accp1, accp2), one lateral middlesized sensillum (accp3) thick and tubular, and one ventral (Figures 4B, 6A). Microsensilla thick and long. Macrochaetae with few cilia, 1,1/3,3,3,4 in number, medial ones on Abd.V three times longer than inner edge of unguis. Ciliate foil setae arranged in two transversal rows as 3 + 3 anterior (fa1, fa3, fa5) and 5 posterior (fp0, fp2, fp4) (Figure 6A). Thorax without ventral setae.

Unguis of normal shape, without lateral and inner teeth. Empodial appendage about half as long as unguis. Tibiotarsi with additional setae on all legs (Figure 6D). Tibiotarsal tenent setae pointed. Ventral tube with 4 + 4 laterodistal and with 4 posterior setae arranged in two transversal rows, anteriorly without setae. Tenaculum with 4 + 4 teeth and one seta. Anterior furcal subcoxae with 11–12, posterior with 7 setae. Anterior side of manubrium with 1 + 1 setae (Figure 6B). Dens with 12–13 anterior setae. Posterior side of dens crenulated and with 5 normal setae (3 basal and 2 at the middle) and one rudimentary minute seta near the base of mucro (Figure 6B, C). Mucro short, bidentate. Manubrium about half as long as dens.

The species was already partly described by us under the name Micrisotoma sp.1 (Potapov 2002). It can be easily identified because of extraordinary foil setae unknown in the family Isotomidae. Such a form of a foil seta could be derived from a common foil seta if the ciliated portion of a seta gets maximal development. The body size of adult stage of this species is not known since we have no mature specimens. By the same reason our figures for number of setae could be underestimated. Nonetheless, the new species appears to be so distinct that we dare to describe it.

The new species is armed with peculiar foil setae.