Allonychiurus antennalis Xin, Jian-Xiu & Louis 2011

Body length: 1.3–1.7 mm (females), 1.0 mm (males). Body shape cylindrical, Abd. III–IV more or less broadened. Body colour white in alcohol. Pseudocellar formulae as 32/133/33343 dorsally, 11/000/01000 ventrally (Figs 1A, B), subcoxa 1 of legs I, II and III with 1, 1 and 1 pso respectively. Parapseudocelli absent. Pseudopore formulae as 00/011/11110 dorsally, 00/111/000x0 ventrally (Figs 1A, B). S-chaetae formula as 11/012/222120 dorsally. Sp present on head. S-microchaetae tiny and blunt, present on Th. II and III dorsally (Fig. 1A). Head. Antennae short and distinctly segmented, as long as head (Fig. 1A). Length ratio of antennal segments I: II: III: IV = 1: 1.8–2: 1.8–2: 3.8–4.0. Ant. I with 9–10 chaetae. Ant. II with 14–15 chaetae. Ant. III sensory organ composed of 5 papillae, 5 guard chaetae, 2 small rods and 2 weakly granulated sensory clubs, both morel-like; lateral ms just posterior to sensory organ (Fig. 1C). Ant. IV subapical organite rod-like; basolateral ms at about 2/5 length from base; presence of a small, finely granulated (probably only primary granulation), flat apical swelling at the apex of antenna (possibly remnant of apical bulb fused to the apex) (Fig. 1D); invaginated apical bulb absent. Antennal base with distinct granulation. PAO composed of 18–22 compound vesicles arranged in 2 rows along axis of organ (Fig. 1A). Dorsal cephalic chaeta d0 present. 4+4 p-chaetae between posterior a-pso on head (Fig. 1A). Mandible with strong molar plate and 4 apical teeth. Maxilla bearing 3 teeth and 6 lamellae. Maxillary palp simple with 1 basal chaeta and 2 sublobal hairs. Labral chaetae formula 4/342. Labium with 6 proximal, 4 basomedian (E, F, G, and f) and 6 basolateral (a, b, c, d, e, e’) chaetae;labial papillae of AC type, papillae A–E respectively with 1, 3, 0, 3 and 3 guard chaetae (Fig. 1E). Postlabial chaetae 4+4 along ventral groove (Fig. 1F). Body chaetotaxy. Ordinary chaetae differentiated in meso- and macro-chaetae, ratio Sp: m1: p1 on Abd. V = 1: 0.6: 1.1 (Fig. 1A). Th. I with 7+7 chaetae dorsally. Three chaetae on both side of axial line and no uneven axial chaetae from Th. II to Abd. III tergites. Abd. IV tergite with two uneven axial chaetae (m0 and p0 ), Abd. V tergite with one uneven axial chaeta (m0), Abd. VI with two uneven axial chaetae (a0 and p0) (Fig. 1A). Th. I, II and III sternites with 0+0, 1+1 and 1+1 chaetae respectively. Appendages. Subcoxa 1 of legs I, II and III with 4, 4 and 4 chaetae, subcoxa 2 with 1, 4 and 4 chaetae, respectively. Tibiotarsi of legs I, II and III with 22 (11, 8, 3), 21 (11, 8, 2) and 21 (11, 8, 2) chaetae. Unguis without tooth. Unguiculus slender and pointed, 0.6 times as long as inner edge of unguis, with narrow inner basal lamella (Fig. 1G). Ventral tube with 6+6 distal chaetae, anterior and basal chaetae absent (Fig. 2A). Furca reduced to a finely granulated area, with 4 short chaetae in two rows posterior to furcal rudiment (Fig. 1H). Male genital plate with 30 circumgenital and 8 genital chaetae (Fig. 2B); female genital plate with 16–18 anterior and 2 genital chaetae (Fig. 2C). No modified chaetae ventrally in males. Anal valves with numerous acuminate chaetae; each lateral valve with chaetae a0 and 2 a1; upper (posterior) valve with chaetae a0, 2 b1, 2 b2, c0, 2 c1, 2 c2 (Fig. 2D). Anal spines set on distinct papillae, 0.6 times as long as inner edge of leg III unguis (Fig. 2E).