Lithobius (Ezembius) hualongensis sp. nov. and Lithobius (Ezembius) sui sp. nov. (Lithobiomorpha, Lithobiidae), two new species of centipede from northwest China

Abstract Lithobius (Ezembius) hualongensissp. nov. and Lithobius (Ezembius) suisp. nov. (Lithobiomorpha, Lithobiidae) recently discovered from the Qinghai-Tibet Plateau, China are described. Morphologically, the two new species are very similar but can be distinguished by the number of coxosternal teeth: L. (E.) hualongensissp. nov. has 2 + 2 while L. (E.) suisp. nov. has 3 + 3. The two new species resemble L. (E.) multispinipesPei et al., 2016, from the Xinjiang Autonomous Region, but can be readily distinguished by having the Tömösváry’s organ slightly larger than the adjoining ocelli rather than smaller, 3 + 3 spurs on female gonopods versus 2 + 2, and the simple terminal claw of female gonopods with a small triangular protuberance on the basal ventral side versus simple, without a small triangular protuberance on the basal ventral side. We also compare the main morphological characters of the two new species with the other Lithobius (Ezembius) species known in Qinghai Province. A key to the Chinese species of Ezembius is presented.


introduction
The myriapod fauna of China is still poorly known and this is especially the case with centipedes of the order Lithobiomorpha. Only about 84 species/subspecies of lithobiomorphs are known from the country (Ma et al. 2014a(Ma et al. , b, 2015Pei et al. 2014Pei et al. , 2015Pei et al. , 2016Pei et al. , 2018Qin et al. 2014;Qiao et al. 2018aQiao et al. , b, 2019a. Qinghai province is among the very poorly studied regions of China with only 11 species at present registered from its territory (Ma et al. 2014b, Qiao et al. 2018a, b, 2019a. Altogether, 26 species of Lithobius (Ezembius) have been recorded from China (Zhang 1996;Pei et al. 2018, Qiao et al. 2018b, 2019a. Herein we describe Lithobius (Ezembius) hualongensis sp. nov. found in Hualong County, Qinghai and Lithobius (Ezembius) sui sp. nov. collected from Minghe County, Qinghai.
The centipede subgenus Ezembius was erected by Chamberlin (1919) as a genus to receive Lithobius stejnegeri Bollman, 1893, L. ostiacorum Stuxberg, 1876, L. princeps Stuxberg, 1876, L. sulcipes Stuxberg, 1876and L. scrobiculatus Stuxberg, 1876 and then was formally proposed as new and described in 1923 (Chamberlin 1923). It accommodates a group of 58 species/subspecies known mostly from Asia, but also western North America and spans a wide range of habitats, from the arctic and sub-arctic to tropical and sub-tropical forests, to steppe and overgrazed stony areas of central Asia, to Himalayan montane forests, from the sea shore up to 5500 m (Himalayas) (Zapparoli and Edgecombe 2011). Most of species are not widely distributed (Bonato et al. 2016), except Lithobius (Ezembius) giganteus Sseliwanoff, 1881 distributed in Mongolia, eastern Kirgizia Buryat and Soviet Central Asia (Eason 1986) and Lithobius (Ezembius) sibiricus Gerstfeldt, 1858 distributed in Asian Russia in Western, Central and Eastern Siberia, the Russian Far East and northern Mongolia (Eason 1976).

Materials and methods
All specimens were hand-collected under leaf litter or stones. The material was examined with the aid of a Motic-C microscope of which the measuring accuracy is +/-0.01 mm. The color description is based on specimens in 75% ethanol, and body length is measured from the anterior margin of the cephalic plate to the posterior end of the postpedal tergite. Type specimens are preserved in 75% ethanol and deposited in Northwest Institute of Plateau Biology, Chinese Academy of Sciences. The terminology of the external anatomy follows Bonato et al. (2010). The following abbreviations are used in the text and the tables: a anterior; C coxa; D dorsal; F femur; m median; p posterior; P prefemur; S, SS nsternite, sternites; T, TT n tergite, tergites; Diagnosis. A Lithobius (Ezembius) species with body length 12.31-16.15 mm, antennae of 20 + 20 articles; 8-11 ocelli on each side, arranged in 3 irregular rows, terminal two ocelli comparatively large; Tömösváry's organ distinctly larger than the adjoining ocelli; 2 + 2 coxosternal teeth; porodonts posterolateral and ventral to the lateral-most tooth; posterior angles of all tergites without triangular projections; 4-7 coxal pores oval to round, arranged in one row; female gonopods with 3 + 3 moderately large, coniform spurs; terminal claw of the third article simple, with a very small triangular protuberance on basal ventral side; male gonopods short and small, with one long setae on the terminal segment.
Coloration. Body and antennae reddish brown. Pleural region pale grey. Sternites yellow-brown. Distal part of forcipules red-brown, with basal and proximal parts of forcipules and forcipular coxosternite yellow-brown. Legs 1-15 pale yellow-brown.
Antennae composed of 20 + 20 articles extending back to anterior part of T3, basal article about the same width as length, second article longer than wide, third article slightly longer than wide, with following articles tapering, distal-most article 2.7 times as long as wide; abundant setae on antennal surface, gradual increase in density of setae to about 4 th article, then more or less constant. Cephalic plate smooth, cordiform. Frontal marginal ridge of head with shallow anterior median furrow. Lateral marginal ridge discontinuous. Posterior margin continuous, convex (Fig. 1A).
On each side of head, 1 + 3, 3, 1 oval to rounded ocelli arranged in three irregular rows; posterior ocellus large; ocelli adjacent to the Tömösváry organ slightly smaller. Seriate ocelli domed, translucent, usually darkly pigmented. Tömösváry organ at anterolateral margin of the cephalic plate, larger than the adjacent ocelli.
Coxosternite subtrapezoidal (Fig. 1C) with narrow dental straight dental margin, anterior margin narrow, lateral margins of the coxosternite longer than medial margins. Median diastema shallow; anterior margin with 2 + 2 small blunt teeth that are encircled by a narrow rim. Porodont thick and strong, just posterolateral and ventral from the lateral tooth, bulged at base (Fig. 1C). Scattered short and long setae on the ventral side of coxosternite, longer setae near the porodont.
All tergites with numerous minute setae scattered on surface, several setae on anterior and posterior angles of each tergite and lateral borders, dorsum slightly convex; T1 slightly narrower posterolaterally than anterolaterally, generally trapezoidal, slightly narrower than the cephalic plate and T3, cephalic plate slightly about the same size as T3. Lateral marginal ridges of all tergites continuous. Posterior marginal ridges of TT 1, 3 and 5 concave, continuous, posterior marginal ridges of TT 7, 8, 10, 12 and 14 slightly concave, discontinuous. Posterior angles of all tergites rounded, without triangular projections.
Sternites smooth, posterior part of sternites narrower than anterior, generally trapezoidal. Sternites with 8 short to long setae on anterior corners and anterior lateral borders, 2 setae on posterior lateral borders.
Legs slender, tarsal articulation well defined on legs 1-15. All legs with fairly long curved claws; pretarsus of legs 1-13 with a slightly curved, long, principal claw and anterior and posterior accessory spines, anterior accessory spines slightly longer and slender, ca 0.56 the length of principal claw, posterior one stouter, ca 0.43 the length of principal claw, forming slightly larger angles with tarsal claws; leg 14 with only posterior spines; leg 15 lacking accessory spines. Dense glandular pore on surface of femur, tibia and tarsi of legs 14 and 15. Long setae sparsely scattered over surface of prefemur, femur, tibia, and tarsi of legs 14-15, more setae on the tarsal surface. 6-7 thicker setae arranged in one row on the ventral surface of tarsus 1 of legs 1-13, 6-7 pairs of thicker setae arranged in two rows on the ventral surface of tarsus 2 of legs 1-13. Legs 14 and 15 thicker and stronger than the anterior pairs. 15 th leg 40.6% of body length, tarsus 1 3.3 times longer than wide, tarsus 2 44.4% length of tarsus on leg 15. No modification on legs 14 and 15 in males. Leg plectrotaxy as in Table 1.
Coxal pores 4655 round or slightly oval, variable in size, arranged in a row. Coxal pore field set in a relatively shallow groove, the coxal pore-field fringe with prominence. Prominence with short to moderately long setae sparsely scattered over the surface.
Male posterior segment. Male S15 subtrapeziform, posterior margin narrower than anterior, sparsely covered with short to long setae on ventral side of S15 and  1D); sternite of genital segment obviously smaller than the female, sclerotized; posterior margin deeply concave between the gonopods, without medial bulge. Long setae scattered on the ventral surface of the genital segment. Gonopods short, appearing as a small hemispherical bulge, with one long setae, apically slightly sclerotized (Fig. 1D). Female posterior segment. Female S15 anterior margin broader than posterior, generally trapezoidal, posteromedially straight, S15 with short to long setae on the ventral surface and lateral and posterior borders. Posterior margin of genital sternite deeply concave between condyles of gonopods, except for a small, median rhomboid bulge. Short to long setae sparsely scattered on ventral surface of genital segment. Gonopods: first article fairly broad, bearing 17-20 short to moderately long setae, arranged in four irregular rows; with 3 + 3, moderately long and slender spurs, inner spur smaller than the outer (Fig. 1E); second article with 6-7 long setae, arranged in two irregular rows, with 10 short to long dorsal lateral setae, stouter than the general setae (Fig. 1F); third article with 6 long setae arranged in one irregular row, and 7 short setae on dorsal lateral side (Fig. 1F); third article terminal claw simple and sharp, having a very small triangular protuberance on ventral side (Fig. 1E).
Etymology. The new species is named from the type locality.
Habitat. The four specimens here examined (3 ♂♂, 1 ♀) were collected under granular gravel on the alpine meadows composed mainly of Poaceae, Cyperaceae, Fabaceae, Polygonaceae, Chenopodiaceae, Asteraceae, Rosaceae, Liliaceae and Cucurbitaceae. The region is located on the upper reaches of the Yellow River Valley and features an arid climate, with mean annual precipitation 451.2 mm and average annual temperature 2.8 °C (http://data.cma.cn/data/weatherBk.html). Diagnosis. A Lithobius (Ezembius) species with body length 12.15-18.85 mm, antennae of 20 + 20 articles; 9-10 ocelli on each side, arranged in 3 irregular rows, terminal two ocelli comparatively large; Tömösváry's organ distinctly larger than the adjoining ocelli; 3 + 3 coxosternal teeth; porodonts posterolateral and ventral to the lateral-most tooth; posterior angles of all tergites without triangular projections; 4-8 coxal pores oval to round, arranged in one row; female gonopods with 3 + 3 moderately large, coniform spurs; terminal claw of the third article simple, with a very small triangular protuberance on basal ventral side; male gonopods short and small, with two long setae on the terminal segment.
Coloration. Body yellow-brown, cephalic plate and antennae light yellow-brown with reddish hue. Pleural region pale grey. Sternites yellow-brown. Distal part of forcipules red-brown, with basal and proximal parts of forcipules and forcipular coxosternite yellow-brown. Legs 1-15 light yellow-brown.
Antennae composed of 20 + 20 articles extending back to posterior part of T3, basal article about the same width as length, second article slightly longer than wide, third article slightly wider than long, with following articles tapering, distal-most article 2.9 times as long as wide; abundant setae on antennal surface, gradual increase in density of setae basally to distally to about fourth articles.
All tergites with numerous minute setae scattered on surface, several setae on anterior and posterior angles of each tergite and lateral borders, dorsum slightly convex; T1 narrower posterolaterally than anterolaterally, generally trapezoidal, narrower than the  cephalic plate and T3, cephalic plate slightly wider than T3. Lateral marginal ridges of all tergites continuous. Posterior marginal ridges of TT 1 and 3 slightly concave, continuous, posterior marginal ridges of TT 5, 7, 8, 10, 12 and 14 concave, discontinuous. Posterior angles of all tergites rounded, without triangular projections. Sternites smooth, posterior part of sternites narrower than anterior, generally trapezoidal. Sternites with 2-7 short to long setae on anterior corners and anterior lateral borders, the same with posterior lateral and posterior angles.
Legs slender, tarsal articulation well defined on legs 1-15. All legs with fairly long curved claws; pretarsus of legs 1-13 with a slightly curved, long, principal claw and anterior and posterior accessory spines, anterior accessory spines slightly longer and slender, ca 0.50 the length of principal claw, posterior one stouter, ca 0.33 the length of principal claw, forming slightly larger angles with tarsal claws; legs 14 and 15 with only posterior spines. Dense glandular pore on surface of femur, tibia and tarsi of legs 14 and 15. Long setae sparsely scattered over surface of prefemur, femur, tibia, and tarsi of legs 14-15, more setae on the tarsal surface. 7-9 thicker setae arranged in one row on the ventral surface of tarsus 1 of legs 1-13, 7-8 pairs of thicker setae arranged in two rows on the ventral surface of tarsus 2 of legs 1-13. Legs 14 and 15 thicker and stronger than the anterior pairs. 15 th leg 39.24% of body length, tarsus 1 3.8 times longer than wide, tarsus 2 44.4% length of tarsus on leg 15. Leg plectrotaxy as in Table 3.
Coxal pores 4-8 round or slightly oval, variable in size, arranged in a row. Coxal pore field set in a relatively shallow groove, the coxal pore-field fringe with prominence. Prominence with short to moderately long setae sparsely scattered over the surface.
Female posterior segment. Female S15 anterior margin broader than posterior, generally trapezoidal, posteromedially straight, S15 with short to long setae on the ventral surface and lateral and posterior borders. Posterior margin of genital sternite deeply concave between condyles of gonopods, except for a small, median rhomboid bulge. Short to long setae sparsely scattered on ventral surface of genital segment. Gonopods: first article fairly broad, bearing 9-11 short to moderately long setae, arranged in three irregular rows; with 3 + 3, moderately long and slender, bullet-shape spurs, inner spur smaller than the outer (Fig. 2E); second article with 6-7 long setae, arranged in two irregular rows, with 10 short dorsal lateral setae, stouter than the general setae (Fig. 2G); third article with 6 long setae arranged in one irregular row, and 7 short setae on dorsal lateral side (Fig. 2G); third article terminal claw simple and sharp, having a very small triangular protuberance on ventral side (Fig. 2E).
Male posterior segment. Male S15 subtrapeziform, posterior margin narrower than anterior, sparsely covered with short to long setae on ventral side of S15 and lateral and posterior borders (Fig. 2F); sternite of genital segment sclerotized; posterior margin deeply concave between the gonopods, without medial bulge. Long setae scattered on the ventral surface of the genital segment. Gonopods short, appearing as a small hemispherical bulge, with two long setae, apically slightly sclerotized (Fig. 2F). No modification on legs 14 and 15 in males. Etymology. The specific name is a patronym in honor of the zoologist Dr Jianping Su, Academician at the Chinese Academy of Sciences.