Theatops chuanensis Di, Cao, Wu, Yin, Edgecombe & Li, 2010, n. sp.

Theatops chuanensis n. sp.

Figs. 2–19

Type specimens: Holotype: China: Sichuan Province, Nanping County, Jiuzhai Valley; leg. Zhiyong Di, viii.2009; MWHU (Ar.-MWHU-SCJZ0908).

Diagnosis: Prefemur and femur of ultimate leg lacking spines on ventral side; dorsal distomedial prefemoral spur absent; medial border of coxopleuron slightly prolonged posteriorly, acuminate, bearing a small spine at apex; pore field extending near to posterior margin of coxopleuron; 10 pairs of round spiracles, on segments 3, 5, 7, 8, 10, 12, 14, 16, 18 and 20.

FIGURES 12–18. Theatops chuanensis n. sp. holotype. 12–13. Head and tergite 1 and 2, dorsal and ventral views. 14. Right lateral view of 7th and 8th segments. 15. Spiracle. 16–18. Legs 1 (left), 18 (right) and 20 (left). Scale bars (except 15): 2.5 mm, scale bar(15): 0.25 mm.

Etymology: The specific epithet refers to the locality where the specimen was collected. The prefecture name “Chuan” is compounded with the suffix “ensis”.

Description: Length 76.6 mm (Figures 2–3).

Cephalic plate, coxosternite and forcipules, T1–2, ultimate segment and ultimate legs pale orange (Figures 2–3). Antennae, T3–20, all sternites, and dorsal aspects of legs light yellow. Margin of coxosternal tooth plates, tibial and tarsal spurs, and distal parts of pretarsi red-brown. Ventral aspects of legs pale yellow with nearly white patches.

Tegument smooth. Cephalic plate rounded, about as long as wide, overlapping T1; two pale areas instead of lateral ocelli at base of antennae (Figures 4, 12); pair of unequal, longitudinal sutures on posterior part of cephalic plate, the longer less than half length of cephalic plate, terminating slightly anteriad of posterior margin (Figure 12). Antenna extending to posterior end of T5, with 17 articles, the basal four bearing very few scattered setae dorsally; 1st article sparsely setose ventrally, increasing to moderately setose by 3rd and densely setose at 5th article (Figure 13). Coxosternal tooth plate narrowing distad, with 1–2 teeth, where paired, situated near medial and lateral margins (Figure 13); trochanteroprefemoral process thorn-like.

T1 with anterior transverse sulcus and cruciform sutures (Figures 2, 8, 12); former straight for most of its length, forming obtuse angle at midline; anterior halves of cruciform sutures bissected by longitudinal median furrow continuing anterior to the anterior transverse sulcus. T2–20 with pair of complete paramedian sutures (Figure 9); T2–5 additionally with bilobate transverse suture between anterior part of paramedian sutures and oblique sutures across more than half of tergites lateral to paramedian sutures (Figure 8). T21 with longitudinal median suture terminating just short of caudal margin; length of tergite nearly twice width. Sternites 1–20 with round median depressions. S21 attenuated posteriorly, elongate subtriangular, lateral margins weakly concave, posteromedian margin with slight indentation (Figures 7, 11). Segments 3, 5, 7, 8, 10, 12, 14, 16, 18 and 20 with rounded spiracles (Figures 14–15); spiracle on segment 7 as large as that on segment 8. Each coxopleuron with ovoid field of several hundred small pores, pore field extending close to posterior margin; medial border of coxopleuron slightly prolonged posteriorly, acuminate, bearing a small red-brown spine at apex (Figure 11).

Two tibial spurs on legs 1–18, leg 19 damaged (tibia absent), leg 20 without tibial spurs (Figure 18). Legs 1–20 each with a tarsal spur near distal end of tarsus (Figures 14, 16, 17) and a pair of pretarsal accessory spurs. Ultimate legs forcipulate, prefemora subquadrate in cross-sections, ventral sides of prefemora and femora without spines (Figures 6–7, 10–11).

Ecology: Under stones in moist, warm mixed forest.

Distribution: Known only from the type locality (Figure 19).

Discussion: Based on the shared absence of a dorsal distomedial prefemoral spur on the ultimate leg and the suppression of ventral spines on the prefemur and femur of that leg, T. chuanensis appears to be closely related to T. californiensis and T. posticus. The most pronounced difference between them is the presence (T. chuanensis) or absence (North American species) of the segment 7 spiracle. The holotype of T. chuanensis wholly lacks ventral spines on the prefemur and femur of the ultimate leg, a state variably shared with T. californiensis (Shelley 1997: fig. 17) and T. posticus (Shelley 1990: fig. 6), notably the eastern population of the latter, though both of the American species more often have a single spine on each prefemur and femur. T. chuanensis is further distinguished from T. posticus by the distinct prolongation of the coxopleuron and the presence of a spine at its apex, as well as by the closer approximation of the pore field to the posterior margin (compare Figure 11 and Shelley 1990: figs. 6–11). The pore field of T. chuanensis is longer than in any of four North American species of Theatops, and is most closely approached by that of T. erythrocephalus (Shelley 1990: fig. 12; Shelley 1997: figs. 40–41).

The discovery of Theatops in China demonstrates that Plutoniumidae is much more widely distributed geographically than had been thought to be the case. The (then reasonable) inference by Shelley (1997) that taxa in Asia are unlikely to belong to Plutoniumidae is no longer tenable on geographic grounds alone. It is likely that this family had a very widespread distribution that is now reduced to highly disjunct parts of the world (North America, the Mediterranean Basin, and China), pruned by extinction. The type locality of Theatops chuanensis lies near the limits of published myriapod localities in China mapped by Wang & Mauriès (1996). Their map showed vast areas of China that remained to be surveyed by myriapodologists, and they judged that probably only a small percentage of Chinese myriapod species had yet to be discovered and described. The completely unexpected discovery of a Chinese plutoniumid during a field excursion as recently as 2009 demonstrates the enormous potential for further surveys of previously unexplored or undersampled parts of China to find species that are of global biogeographic significance.