Tomocerus nuwa sp. nov.

Figs 1A, 2A–D, 3, 4

Type material. Holotype female on slide, Lishan Mountain, Xi'an, Shaanxi Province, China, 109°12'37.7352"E, 34°21'39.834"N, alt. 665± 6m, 21.xi.2016, by Daoyuan YU (No. 16NW11). Paratypes 2 female and 1 subadult on slides, 2 in alcohol, same data as holotype. All types deposited in NJAU.

Description. Body length 1.7–2.1mm. Body ground colour pale yellow, with diffuse grey pigment, head darker. Antennae purple. Eye patches black. (Fig. 1A).

Antennae short, 0.45–0.5 times as long as body. Length ratio of Ant. I:II:III:IV= 1.0:1.4–1.5:4.4–5.4:2.2–2.4. Both dorsal and ventral sides of Ant. I and Ant. II scaled, Ant. III and Ant. IV unscaled. PAO not seen. Eyes 6+6, front 2 larger. Labral formula 4/5, 5, 4. Distal edge of labrum with four curved spines. Mandibular head asymmetrical, left one with 4 teeth and right one with 5, left molar plate distally with a tapered tooth (Fig. 3A). Maxillary lamella 5 with short teeth, without beard-like appendage (Fig. 3B). Maxillary outer lobe with trifurcate palp and one basal chaeta (Fig. 3C), sublobal plate with 4 hairs. Both dorsal and ventral sides of head scaled.

Cephalic dorsal macrochaetotaxy: anterior area: 2, 4; interocular area: 2, 7, central unpaired macrochaeta present; postocular area: 3+3; posterior area: 1+1. Posterior margin of head with approximately 20+20 chaetae (Fig. 3D). Mentum with 5 chaetae, submentum with numerous chaetae.

Pattern of body chaetotaxy as in Fig. 3E. Bothriotricha 1, 1/ 0, 0, 1, 2, 0, 0 on Th. II–Abd. VI. Macrochaetae densely arranged along anterior margin of Th. II (not shown in figure). Th. II with an irregular row of macrochaetae behind anterior margin. Number of macrochaetae or large mesochaetae in the posterior row as 3, 3/ 3, 3, 3–4, 2, 4 from Th. II to Abd. V. Th. II with four central and one lateral macrochaetae, postero-central one near pseudopore; Th. III with anterior macrochaeta; Abd. III with two anterior macrochaetae; Abd. IV with one antero-lateral macrochaeta; Abd. VI with numerous chaetae of different sizes. Mesochaetae most abundant laterally and posteriorly on terga. Pseudopores near the axis of terga, 1, 1/ 1, 1, 1, 1, 0, 0 from Th. II to Abd. VI.

Trochantero-femoral organ with 1, 1 slender chaetae (Fig. 3F). Anterior and mid tibiotarsi without ventral spine-like chaetae, hind tibiotarsi disto-ventrally with 2 spine-like chaetae (Fig. 3G). Each tibiotarsus with a distal whorl of 11 chaetae, ventral 6 as ordinary chaetae, dorsal 5 modified: tenent hair clavate on all legs, about 0.9–1.0 times as long as inner edge of unguis; two accessory chaetae slender, longer than pretarsal chaetae; two guard chaetae about as long as tenent hair. Unguis slender, with baso-internal ridges about 1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with 5–6 teeth, basal tooth small, sub-basal tooth subequal to or slightly larger than distal teeth. Unguiculus lanceolate, about 0.6–0.7 times as long as inner edge of unguis, without tooth. Pretarsus chaetae 1+1 (Fig. 3H).

Ventral tube scaled on both anterior and posterior faces, lateral flaps unscaled. Anterior face with 12–15 chaetae on each side, posterior face with 10–15 chaetae, each lateral flap with 25–30 chaetae. Rami of tenaculum with 4+4 teeth, anterior face with 1–2 chaetae and without scales (Fig. 4A). Ratio manubrium:dens:mucro=2.6– 2.8:3.0–3.2:1.0. Manubrium ventrally scaled and without chaetae; laterally with large round scales and 9–10 chaetae on each side, proximal chaeta small, distal ones strong; dorsally with two longitudinal chaetal strips, each with approximately 60–80 chaetae of different sizes, including 1+1 chaetae larger than others, without scales; pseudopores 4–6 on each side (Fig 4B); disto-external corner of manubrium with a microchaeta (manubrial distal corner chaeta, Fig. 4C). Dens basally without distinct prominent dorsal chaeta, large modified inner scale or strong outer chaetae. Dental spine formula as 3–6, III/3–4, I in adult, 2, II/2, I in subadult, proximal spines arranged in 2– 3 irregular rows (Fig. 4D); all spines simple, “smooth” with fine longitudinal ribs (Fig. 2C). Dens dorsally with ordinary chaetae and feather-like chaetae, ventrally with dense scales. Mucro elongated, bearing numerous chaetae with elongated sockets (not shown in figure); both basal teeth with proximal lamellae, outer basal tooth with minute or moderate sized toothlet; apical tooth longer than subapical one. Mucro without intermediate tooth, dorsally with a broad rugose inner lamella, running from distal edge of subapical tooth, ending at base of mucro beside inner basal tooth; outer lamella reduced into short extensions of subapical and inner basal tooth (Fig. 2D; 4E, F).

Etymology. Named after the ancient goddess Nuwa. In the Chinese myth Nuwa was one of the Creators and saved the world by patching the collapsing sky using the stones from Lishan Mountain, the type locality of the new species.

Ecology. In mixed litter of coniferous and broad leafs.

Remarks. Tomocerus nuwa sp. nov. is very similar to Tomocerus violaceus Yosii, 1956 in the small body size, the short antennae and the shape and arrangement of dental spines, but differs from the later mainly in the number and arrangement of tibiotarsal strong inner chaetae (Yosii 1967), the number of mucronal intermediate teeth and the structure of mucronal dorsal lamellae (Table 1). Despite of the presence of a minute toothlet on mucronal outer basal tooth, which is an unstable generic character (Yu et al. 2014, Yu & Li 2016), T. nuwa sp. nov. also resembles two species of Tomocerina: Tomocerina yiliensis Ma, Chen & Christiansen, 2003 (in Ma et al. 2003a) and Tomocerina tianshanensis Ma, Chen & Christiansen, 2003 (in Ma et al. 2003b), in the short antennae, the tibiotarsal strong inner chaetae and the shape and arrangement of dental spines, but is different from the laters mainly in the cephalic dorsal chaetotaxy, the number of mucronal teeth and the structure of mucronal dorsal lamellae (Table 1).

Type material. Holotype female on slide, Jifeng Mountain, Cheng County, Longnan, Gansu Province, China, 105°40'49.1952"E, 33°40'59.639"N, alt. 1747± 9m, 19.xi.2016, by Daoyuan YU (No. 16NW6). Paratypes 1 male on slide, 6 in alcohol, same data as holotype; 3 female and 2 male on slides, 10 in alcohol, 105°40'52.122"E, 33°41'21.1452"N, alt. 1887± 9m (No. 16NW4), other data same as holotype. All types deposited in NJAU.

Description. Body length 2.2–2.8mm. Body ground colour greyish white, with scattered dark grey pigment. Antennae and anterior area of head darker. Eye patches black. (Fig. 1B).

Antennae short, 0.4–0.46 times as long as body. Length ratio of Ant. I:II:III:IV= 1.0:1.5–1.9:4.7–5.6:2.1–2.6. Both dorsal and ventral sides of Ant. I and Ant. II scaled, Ant. III and Ant. IV unscaled. PAO not seen. Eyes 6+6, front 2 larger. Labral formula 4/5, 5, 4. Distal edge of labrum with four curved spines. Mandibular head asymmetrical, left one with 4 teeth and right one with 5, left molar plate distally with a tapered tooth. Maxillary lamella 5 with short teeth, without beard-like appendage (Fig. 5A). Maxillary outer lobe with trifurcate palp, one basal chaeta and 4 sublobal hairs (Fig. 5B). Both dorsal and ventral sides of head scaled. Cephalic dorsal macrochaetotaxy: anterior area: 2, 2; interocular area: 2, 7, central unpaired macrochaeta present; postocular area: 3+3; posterior area: 1+1. Posterior margin of head with approximately 30+30 chaetae (Fig. 5C). Mentum with 5 chaetae, submentum with numerous chaetae.

Pattern of body chaetotaxy as in Fig. 5D. Bothriotricha 1, 1/ 0, 0, 1, 2, 0, 0 on Th. II–Abd. VI. Macrochaetae densely arranged along anterior margin of Th. II (not shown in figure). Th. II with an irregular row of macrochaetae behind anterior margin. Number of macrochaetae or large mesochaetae in the posterior row as 3, 3/ 3, 3, 3–4, 2, 4 from Th. II to Abd. V. Th. II with five central and one lateral macrochaetae, postero-central one near pseudopore; Th. III with anterior macrochaeta; Abd. III with two anterior macrochaetae; Abd. IV with one antero-lateral macrochaeta; Abd. VI with numerous chaetae of different sizes. Mesochaetae most abundant laterally and posteriorly on terga. Pseudopores near the axis of terga, 1, 1/ 1, 1, 1, 1, 0, 0 from Th. II to Abd. VI.

Trochantero-femoral organ with 1, 1 slender chaetae (Fig. 5E). Anterior and mid tibiotarsi without ventral spine-like chaetae, hind tibiotarsi disto-ventrally with 2 spine-like chaetae (Fig. 5F). Each tibiotarsus with a distal whorl of 11 chaetae, ventral 6 as ordinary chaetae, dorsal 5 modified: tenent hair short, clavate on all legs, about 0.6–0.7 times as long as inner edge of unguis; two accessory chaetae slender, about as long as pretarsal chaetae; two guard chaetae 1.2–1.5 times as long as tenent hair and 0.7–0.8 times as long as inner edge of unguis. Unguis slender, with baso-internal ridges about 1/4–1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with 4–5 teeth, basal tooth small, sub-basal tooth larger than distal teeth. Unguiculus lanceolate, about 0.6–0.7 times as long as inner edge of unguis, with small inner tooth. Pretarsus chaetae 1+1 (Fig. 5G).

Ventral tube scaled on both anterior and posterior faces, lateral flaps unscaled. Anterior face with 20–35 chaetae on each side, posterior face with 50–60 chaetae, each lateral flap with 50–60 chaetae. Rami of tenaculum with 4+4 teeth, anterior face with 2–6 chaetae and without scales (Fig. 6A). Ratio manubrium:dens:mucro=2.7– 3.2:3.3–3.8:1.0. Manubrium ventrally scaled and without chaetae; laterally with large round scales and 9–11 strong chaetae on each side, proximal chaeta smaller; dorsally with two longitudinal chaetal strips, each with approximately 200 chaetae of different sizes, without scales or distinct prominent chaetae; pseudopores 7–13 on each side; manubrial distal corner chaeta absent (Fig. 6B). Dens basally without distinct prominent dorsal chaeta, large modified inner scale or strong outer chaetae. Dental spine formula normally as 5–7, III/2–4, I, 1, I (Fig. 6C), in one specimen as 7, II/3, III on left and 7, III/3, I, 1, II on right. Proximal spines arranged in 2–3 irregular rows. All spines simple, “smooth” with fine longitudinal ribs (Fig. 2F). Dens dorsally with ordinary chaetae and featherlike chaetae, ventrally with dense scales. Mucro elongated and multi-setaceous; both basal teeth with proximal lamellae, outer basal tooth with or without minute toothlet; apical tooth longer than subapical one. Mucro without intermediate tooth, dorsally with a rugose inner lamella, running from distal edge of subapical tooth (Fig. 2G), ending beside inner basal tooth; outer lamella reduced (Fig. 6D, E).

Etymology. Named after the ancient god Fuxi. In the Chinese myths Fuxi was another Creator, the brother and husband of Nuwa, and was born near the type locality of the new species in Gansu Province.

Ecology. In coniferous litter in sample 16NW6, in mixed litter of coniferous and broad leafs in sample 16NW4.

Remarks. Tomocerus fuxi sp. nov. is similar to T. nuwa sp. nov. particularly in the special mucronal structure, and also in the single bothriotrichum on Th. II, the number and position of ventral spine-like chaetae on tibiotarsi and the arrangement of proximal dental spines. But in T. fuxi sp. nov. the arrangement of spines in the middle subsegment of dens is different from that in T. nuwa sp. nov. Besides, the two new species can be also distinguished by the chaetotaxy on head and on Th. II, the number of manubrial pseudopores and the status of manubrial distal corner chaeta (Table 1). Similar to T. nuwa sp. nov., T. fuxi sp. nov. resembles also T. violaceus, T. yiliensis and T. tianshanensis, but differs from the laters mainly in the cephalic chaetotaxy, the distal formula of dental spines and the morphology of mucro. Besides, to our knowledge, the manubrial distal corner chaeta is present in most species of Tomocerus but is absent in T. fuxi sp. nov.