Tomocerus (Ocreatomurus) oppositus, Yu & Xue & Zhang, 2025

Tomocerus (Ocreatomurus) oppositus sp. nov.

Figs 15–28 View FIGURES 15–16 View FIGURES 17–22 View FIGURES 23–28 , Table 1 View TABLE 1

Type material. Holotype: male on slide, coniferous and broad-leaved mixed forest, Gyirong Valley , Gyirong County, Xigaze , Xizang Autonomous Region, China, 85°21.781′E, 28°22.080′N ( WGS84 ), alt. 2500 m, 7.viii.2018, leg. Daoyuan Yu, Yiming Wei and Chunyan Qin (Sample code 18XZ16) GoogleMaps . Paratypes: three females and one juvenile on slides, 30 in ethanol, same data as holotype; one female on slide, 18 in ethanol, under a wood board in Jipu Village , Gyirong County, Xigaze , Xizang Autonomous Region, China, 85°19.693′E, 28°22.523′N, alt. 2765 m, 7.viii.2018, leg. Daoyuan Yu, Yiming Wei and Chunyan Qin (Sample code 18XZ15). All types deposited in NJAU GoogleMaps .

Description. Body length 3.4–5.1 mm (average 4.3, five specimens). In subadults and small adults, head, body, and coxae deep purple; trochanteres, ventral tube, and manubrium with diffuse purple pigment; Ant. I–II, femora, tibiotarsi, and dens pale or bright yellow; Ant. III basally pale and gradually darker towards apex; Ant. IV purple ( Fig. 15 View FIGURES 15–16 ). In large adults, purple pigment more intense, becoming dark brown, and extending to Ant. I–II, femora, and dens ( Fig. 16 View FIGURES 15–16 ).

Intact four-segmented antennae 0.7–0.8 × length of body (average 0.75, three specimens). Length ratio of A nt I: II: III: IV = 1.0: 1.4–1.6: 7.3–8.5: 1.0–1.6. Ant. III occasionally with 1–2 scales at base. Cephalic dorsal macrochaetotaxy as in Fig. 17 View FIGURES 17–22 . Posterior margin of head with 35–45 chaetae on each side.

Pattern of body macrochaetotaxy as in Fig. 18 View FIGURES 17–22 .

Tibiotarsi I, II, III ventrally with 8–9, 8–10, 6–10 strong chaetae, 5–6, 6–8, 6–9 of them blunt and spine-like, respectively ( Fig. 19 View FIGURES 17–22 ). Tenent hair 0.79–0.86 × the length of inner edge of unguis; accessory chaetae on tibiotarsus I equal to each other and shorter than pretarsal chaetae; on tibiotarsi II and III, anterior accessory chaeta subequal to or slightly longer than pretarsal chaetae, while posterior accessory chaeta shorter than pretarsal chaetae ( Fig. 20 View FIGURES 17–22 ); guard chaetae as long as tenent hair. Unguiculus about 0.57–0.65 × the length of unguis (average 0.61, four specimens), its inner edge with one tooth ( Fig. 21 View FIGURES 17–22 ).

Ventral tube scaled on both faces; anterior face with 35–55 (average 46, five specimens) chaetae on each side; posterior face with 75–100 (average 89, five specimens) chaetae; each lateral flap with 90–180 (average 144, five specimens) chaetae and occasionally 1–3 scales. Anterior face of tenaculum with 10–17 (average 13, five specimens) chaetae and 0–3 scales ( Fig. 22 View FIGURES 17–22 ). Ratio manubrium: dens: mucro = 3.4–4.1: 4.2–5.2: 1.0. Manubrium laterally with 7–11 strong chaetae; dorsally with 170–280 (average 237, five specimens) chaetae of different sizes on each chaetal strip, 12–21 (average 16, five specimens) pseudopores almost arranging in a file and scale strip running from base to about 2/3 length of manubrium ( Fig. 23 View FIGURES 23–28 ). External distal corner chaeta as large as medium-sized mesochaetae in chaetal strip ( Fig. 24 View FIGURES 23–28 ). Dental spine formula sensu Folsom (1913) as 4–6/4–8, 1, basal spines arranged either in one row ( Fig. 25 View FIGURES 23–28 ) or two rows ( Fig. 26 View FIGURES 23–28 ). Denticles on dental spines distributed more densely on ventral side than on dorsal side of spine ( Fig. 27 View FIGURES 23–28 ). Mucro with 4–7 (average six, five specimens) intermediate teeth ( Fig. 28 View FIGURES 23–28 ).

Etymology. The Latin word oppositus (masculine adjective) means “opposite”, referencing the unique color pattern of the new species with dark ground and pale appendages, opposite to most other species of the subgenus with pale ground and darker appendages.

Habitat. In ground litter, dead logs and live mosses on steep slopes in a closed forest; also under a wood board beside a cottage in a village.

Remarks. At first glance, this new species resembles many others of the subgenus Tomocerus (Striatomurus) for its dark body color. However, other characters, particularly the compound dental spines, put it in Ocreatomurus . Within the subgenus, T. (O.) oppositus sp. nov. possesses a unique color pattern with intensely dark ground and pale appendages, which opposes to most other species with pale ground and darker appendages. A few other species of Ocreatomurus , such as T. (O.) postantennalis Yu, Zhang & Deharveng, 2014 , T. (O.) dong Yu & Li, 2016 , T. (O.) deharvengi Yu & Li, 2016 and T. (O.) cthulhu Yu & Li, 2016 , also have dark pigment covering almost the whole body, however, pigment in these species is diffusely distributed, and the whole animals are from light to dark grey, not as intensely dark as T. (O.) oppositus sp. nov. In spite of the color pattern, this new species is most similar to T. (O.) spinulus in the absence of blunt chaetae on manubrium, presence of single large distal dental spine, and small size of denticles on dental spines, but is different from the later mainly in the larger body size, relatively longer antennae (10 %–38 % longer, average 20 %), larger number of blunt inner chaetae on tibiotarsi, and number and position of manubrial prominent chaetae ( Table 1 View TABLE 1 ).

A few variations in macrochaetotaxy exist in T. (O.) oppositus sp. nov. On the head, macrochaeta A3 is absent from the right side in paratype #5, and macrochaeta S0 is absent in paratype #4. On Th. II, macrochaeta m2 is absent from one side in paratypes #2 and #4, whereas chaeta ap5, which is a microchaeta in most types, becomes a small macrochaeta on the left side in paratype #6.