Description of three new species of the genus Allochthonius Chamberlin, 1929 (Pseudoscorpiones: Pseudotyrannochthoniidae) from China

The pseudoscorpion genus Allochthonius Chamberlin, 1929, belonging to the family Pseudotyrannochthoniidae Beier, 1932, is reported from China, and the subgeneric characters of Allochthonius (Allochthonius) are reviewed in detail. Three new species are diagnosed, described and illustrated under the names Allochthonius (A.) fuscus sp. nov., A. (A.) wui sp. nov. and A. (A.) trigonus sp. nov. A distribution map and a key to the species of subgenus Allochthonius (A.) are provided. In addition, Centrochthonius sichuanensis Schawaller, 1995 is transferred to Allochthonius, forming the new combination A. (A.) sichuanensis (Schawaller).


INTRODUCTION
The pseudoscorpion genus Allochthonius was erected by Chamberlin (1929) for the Japanese type species Chthonius opticus Ellingsen, 1907.This genus was later divided into three subgenera, Allochthonius, Urochthonius Morikawa, 1954and Spelaeochthonius Morikawa, 1954, by Morikawa (1960) based on the presence or absence of eyes, carapacal chaetotaxy and characteristics of the cheliceral fixed finger teeth.Muchmore (1967) used the morphology of the coxal spines and carapacal chaetotaxy to transfer Allochthonius (Spelaeochthonius) to Pseudotyrannochthonius Beier, 1930. Harvey (1991, 2009) agreed with this view which is reflected in the catalogue of the Pseudoscorpiones, and which we follow in this paper.Presently, the genus Allochthonius is composed of two subgenera Allochthonius and Urochthonius, which are widely distributed in Japan and South Korea.The subgenus Allochthonius (Allochthonius) is composed of seven species, and Allochthonius (Urochthonius) includes eight species (Harvey 2009).
While examining pseudoscorpion specimens collected by Dr. Min Wu and Prof. Fusheng Huang from southern and western China, we found some Allochthonius specimens belonging to the subgenus Allochthonius (Allochthonius).Three new species are recognized, which are described and illustrated in this paper.In addition, we assess the taxonomic position of Centrochthonius sichuanensis Schawaller, 1995 which has many characteristics of Allochthonius.

MATERIALS AND METHODS
The patterns of description and the terminology follow Chamberlin (1931) and Harvey (1992).This setal formula of the palpal femur mainly follows Vachon (1941), but the difference from his method is that we divided the "ventral" to "posteroventral" and "anteroventral" (rows in sequence anterioranterodorsal-dorsal-posterodorsal-posterior-posteroventral-anteroventral).
The term "rallum" (for flagellum) is adopted following Judson (2007).All specimens are preserved in 75% alcohol and were examined and illustrated under a Leica M165c stereomicroscope with a drawing tube, which was also used for the measurements.Detailed examination was carried out with a Nikon YS100 general optical microscope.Temporary slide mounts were made in glycerol.All measurements are given in mm.The specimens referred here are deposited in the Museum of Hebei University (MHBU), Baoding City, China.

Allochthonius (Allochthonius)
Rallum composed of a biseriate row of about eight to eleven pinnate setae.Chelal finger with well-spaced and prominent marginal teeth, and movable finger with a tubercle between two teeth (Figs. 6,13,21,26).Coxal spines present on coxae I only, consisting of a tubercle expanded terminally into a spray of about four to ten clavate, fan-shaped or gladiate spines.With a well developed bisetose intercoxal tubercle.Palps, chelicerae and legs relatively short and robust.
Distribution: China, Japan, South Korea.Remarks: Allochthonius (Allochthonius) is similar to the subgenus Allochthonius (Urochthonius) in that: the chelal fingers have well-spaced and prominent marginal teeth; coxal spines are only present on coxae I, consisting of a tubercle expanded terminally into a spray of about eight processes, which extend anteriorly and more or less shield the apical process of coxae I (Morikawa 1960).The two subgenera A. (Allochthonius) and A. (Urochthonius) can be distinguished by the presence of four eyes, or blind or rarely with two eyes, respectively, which is consistent with Morikawa's (1960) viewpoint, but the differences from his system is by the dental morphology and tooth number on the cheliceral fixed finger and the number of setae on the cheliceral palm.For instance, Allochthonius (A.) montanus and Allochthonius (A.) shintoisticus both have four eyes, but the cheliceral fixed finger has one large and a few small teeth and five setae on the cheliceral palm in the former, and the cheliceral palm with five setae in the latter.
In addition, while examining the specimens collected from China, we found a significant characteristic in all species: the palpal movable finger has a tubercle between two teeth.This tubercle is present in Allochthonius (A.) tamurai (cf.Sakayori, 2003: 25, fig. 5a;27, fig. 21a), but Sakayori (2003) did not refer to this tubercle in the description.We infer that this characteristic might only exist in the subgenus Allochthonius (Allochthonius), so further study to all species of Allochthonius, with especial attention to the movable chelal fingers, is required.

Remarks:
Centrochthonius sichuanensis Schawaller, 1995 was described from material collected in Wolong Nature Reserve, Sichuan Province, China.The description indicates that the epistome is absent, the coxal spines are on a tubercle, and the carapace has a high number of setae.All of these characters conform to the diagnosis of Allochthonius, not Centrochthonius (M.S. Harvey, pers. comm.).The presence of eyes suggests that it can be treated in the subgenus Allochthonius.We therefore transfer this species to Allochthonius (Allochthonius), and form a new combination, Allochthonius (A.) sichuanensis (Schawaller, 1995).Diagnosis: Chelal palm obviously dark in color; carapacal chaetotaxy (Fig. 1) 8-4-4-2-4 (22); coxal spines present on coxae I and consisting of 10 tridentate blades, each blade with a central spine terminally distinctly expanded as fan-shaped, all situated on a common tubercle (Fig. 4).This new species is closely related to Allochthonius (A.) tamurai from Japan, but can be distinguished from the latter by the number of coxal spines (six blades spines in latter) and by the shape of the coxal spines (gladiate in latter).

Allochthonius (Allochthonius
Etymology: The specific name is derived from the Latin word "fuscus" means dark colored, referring to the color of the chelal palm. Description: Relatively large species.Body (Image 1) yellow, chelal palm strong yellow and other segments of chela pale yellow.Carapace subquadrate and slightly shorter than broad (0.9 times), carapace indistinctly constricted posteriorly; anterior eyes with well developed tapeta and situated on tubercles, posterior eyes less developed tapeta than anterior ones and without eye-tubercles; epistome absent, space between median setae straight or slightly recurved; chaetotaxy 8-4-4-2-4 (22).
Tergal Cheliceral palm with six setae, of which a minute one is located laterally; palm with moderate hispid granulation interiorly and laterally.Fixed finger of holotype (Fig. 2) with six teeth, of which nearly equal length (paratype (Fig. 3) with one large basal and one subapical teeth, between them with two small teeth); movable finger with 14 relatively small teeth of equal length; spinneret absent.Serrula exterior with 17 lamellae, serrula interior with 13 lamellae.Rallum composed of 11 blades with fine barbules, of which the posterior blade is shorter than others.
Palp smooth, femur 2.0 times longer than carapace, setal formula 7-9-4-3-5-5-2; chelal palm distinctly expanded towards internal side, chelal finger straight in dorsal view; fixed finger with 17 teeth, first three and last four teeth smaller than others; movable finger with  18 teeth, all of which nearly equal length and smaller than fixed finger teeth, and with a tubercle between the ninth and tenth teeth from distal end (Fig. 6).
Etymology: The specific name is named after Prof. Min Wu, who collected the specimens.
Cheliceral palm with six setae, of which a minute one is located laterally; palm nearly smooth, but near the base of fixed finger and interior side with distinctly acute granules (Fig. 10); right fixed finger with one large basal and subapical tooth and between them with three small teeth, but the left finger with two large basal teeth and one large subapical tooth, between them two small teeth; movable finger with 13 small teeth of equal length; spinneret absent, serrula exterior with 19 lamellae, serrula interior with 16 lamellae.Rallum composed of 11 dentate blades, of which the posterior one is smaller than others.
Measurements (ratios in parentheses; for the palp, the larger measurements and lower ratios only referring to male).Body length 2.50.Carapace 0.52×0.58(0.9).Chelicera 0.55×0.25 (2.2), movable finger length Diagnosis: Anterior margin of carapace with 27 triangular protuberances of which eight are situated near the anterior eyes (Fig. 17); coxal spines present on coxae I and consisting of seven tridentate blades, each blade with a central branch terminally distinctly expanded as fan-shaped, six spines on a common tubercle and a single spine slightly separate (Fig. 19).This present species resembles Allochthonius (A.) borealis, but is distinguishable from the latter by the number of blades in the rallum (11 blades, in A. trigonus, and eight blades in A. borealis) and the epistome (present in latter).
Etymology: The specific name is derived from the Greek word "trigonon", means triangle, referring to the shape of triangular protuberances on the carapace anterior margin.
Description: Moderately large species.Body bright yellow.Carapace subquadrate and slightly constricted posteriorly, shorter than broad (0.8 times), carapace anterior margin with 27 triangular protuberances of which eight near the anterior eyes; anterior eyes with developed tapeta and situated on eye-tubercles, posterior eyes with less developed tapeta than anterior ones and without eye-tubercles; epistome absent, space between median setae straight or slightly recurved; chaetotaxy 10-4-6-2-4 (26).
Chelicera palm with six setae, of which a minute one located laterally; palm nearly smooth, but near the base of fixed finger with distinct granules (Fig. 18), fixed finger with one large basal and one subapical teeth, between them with two small teeth inserted; movable finger with 18 small teeth of equal length; spinneret absent.Serrula exterior with 17 lamellae, serrula interior with 14 lamellae.Rallum composed of 11 dentate blades, of which the posterior one smaller  than others.Palp smooth, apart from a patch of minute denticles on anterior surface of trochanter (Fig. 20).Femur 1.7 times longer than carapace, setal formula 8-11-4-4-5-2-1; chelal palm distinctly expanded towards internal side; chelal finger straight in dorsal view; chelal fixed finger with 18 teeth, of which the basal two smaller than others; movable finger with 16 teeth, with a tubercle between the sixth and seventh teeth from terminal (Fig. 21).