﻿Five new epigean Lagynochthonius species (Pseudoscorpiones, Chthoniidae) from southern China

﻿Abstract Five new Lagynochthonius species of the pseudoscorpion family Chthoniidae are described, based on morphological characters: Lagynochthoniusduosp. nov., Lagynochthoniusgibbussp. nov., Lagynochthoniushepingensissp. nov., Lagynochthoniushouisp. nov., and Lagynochthoniussanhuaensissp. nov. All specimens were collected from epigean habitats in southern China.


Introduction
The genus Lagynochthonius Beier, 1951, belonging to the family Chthoniidae Daday, 1889, subfamily Chthoniinae Daday, 1889, tribe Tyrannochthoniini Chamberlin, 1962, was erected by Beier (1951) as a subgenus of Tyrannochthonius Chamberlin, 1929, subsequently elevated to generic status by Chamberlin (1962).It can be recognized by the trichobothria ib and isb situated close together in a median or sub-basal position on the dorsum of the chelal hand; the trichobothrium sb situated midway between st and b; the coxal spines commonly long and present only on coxae II; the chelal hand distally constricted (or flask-shaped), base of movable finger with strongly sclerotized apodeme and the modified tooth (td) of the fixed chelal finger displaced onto the prolateral-retrolateral face (Chamberlin 1962;Harvey 1989;Muchmore 1991;Judson 2007;Edward and Harvey 2008).The movable finger of Tyrannochthonius is only slightly sclerotized, and the fixed chelal finger does not have modified tooth (td), which are the most important differences between these two genera (Chamberlin 1962;Harvey 1989;Muchmore 1991).ZooKeys 1198: 101-134 (2024), DOI: 10.3897/zookeys.1198.115609 Jianzhou Sun et al.: Five new epigean Lagynochthonius species from southern China Lagynochthonius pseudoscorpions usually live in litter layer or soil, under rocks and stones, in caves.At present, this chthoniid genus contains 79 species, of which 32 are distributed in China (Hou et al. 2023a;WPC 2024).Because the biodiversity of cave environments has received a high attention in recent years, most of the reported Lagynochthonius species from China are cave-dwelling (Li et al. 2019;Hou et al. 2022aHou et al. , b, 2023a, b), b), and only seven species, Lagynochthonius brachydigitatus Zhang & Zhang, 2014, L. harveyi Zhang & Zhang, 2014, L. leptopalpus Hu & Zhang, 2012, L. medog Zhang & Zhang, 2014, L. niger Hu & Zhang, 2012, L. sinensis Beier, 1967and L. tonkinensis Beier, 1951, are reported in epigean environments.In this study, five new species of Lagynochthonius are described, all of them collected from epigean habitats in southern China.

Specimen preparation and examination
The specimens examined for this study are preserved in 75% ethyl alcohol in a refrigerator at -20 °C and deposited in the Museum of Hebei University (MHBU) (Baoding, China).Photographs and measurements were taken using a Leica M205A stereomicroscope equipped with a Leica DFC550 camera.Drawings was made using the Inkscape software (v.1.0.2.0).Detailed examination was conducted with an Olympus BX53 general optical microscope.All images were edited and formatted using Adobe Photoshop 2017.

Terminology
Terminology and measurements follow Chamberlin (1931) with some small modifications to the terminology of trichobothria (Harvey 1992;Judson 2007) and chelicera (Judson 2007).The chela and legs are measured in lateral view and others are taken in dorsal view.All measurements are given in mm unless noted otherwise.Proportions and measurements of chelicerae, carapace and pedipalps correspond to length/breadth, and those of legs to length/depth.
2.43-2.84× as long as patella; movable chelal finger 1.11-1.27× as long as hand and 0.55 × as long as chela.Setae generally long and acuminate.Chelal palm gradually constricted towards fingers, apodeme complex of movable chelal finger strongly sclerotized.Fixed chelal finger and hand with eight trichobothria, movable chelal finger with four trichobothria, ib and isb situated close together, submedially on dorsum of chelal hand; eb, esb and ist at base of fixed chelal finger; esb and eb at almost the same level and ist slightly distal to esb; it slightly distal to est, situated subdistally; et slightly near to tip of fixed chelal finger, close to chelal teeth; dx situated distal to et; sb slightly closer to st than to b; b and t situated subdistally, t situated at the same level as it and distal to b; est situated distal to b and close to it (Figs 2A, 4A).Fixed chelal finger with sensilla af 1-2 close together, near tip; movable chelal finger with four sensilla: am 1-2 near tip, p 2 slightly distad of p 1 , p 1 slightly distad of sb and very close to chelal teeth (Fig. 4A).Microsetae (chemosensory setae) present on dorsum of chelal hand (Figs 2B, 4B).Both chelal fingers with a row of teeth, spaced regularly along the margin, teeth smaller distally and proximally: fixed finger with 17 or 18 well-spaced, pointed teeth, plus three or four intercalary microdenticles, and a modified accessory tooth on prolateral-retrolateral face (td, slightly distal to dx); movable finger with six or seven well-spaced, pointed teeth, plus nine or ten vestigial, rounded, contiguous basal teeth.
Remarks.Lagynochthonius duo sp.nov.differs from all other epigean species of the genus Lagynochthonius from China except L. medog by the tergal chaetotaxy I-IV: 2: 2: 4: 4. It differs from L. medog in the presence of an epistome, which is absent in L. medog, and in the presence of only fixed chelal fingers with intercalary teeth in L. duo sp.nov., whereas both chelal fingers have intercalary teeth in L. medog (Beier 1951(Beier , 1967;;Hu and Zhang 2012a, b;Zhang and Zhang 2014).
Distribution.China (Guangxi).Etymology.The specific name is derived from the Latin word gibbus, meaning hump-shaped, which refers to the shape of epistome.A noun in apposition.
Cephalothorax (Figs 7D, 8A): carapace nearly subquadrate, 0.97-1.03× as long as broad, weakly constricted basally; posterior region with squamous sculpturing laterally, other area smooth, without furrows; anterior margin smooth, without serrate; epistome small and hump-shaped; four eyes, anterior pair of eyes well-developed, posterior pair with flat lenses; with 18 setae arranged s4s: 4: 4: 2: 2, most setae heavy, long and gently curved, anterolateral setae much shorter than others; with two pairs of lyrifissures, first pair situated middle to the setae of ocular row, second pair situated lateral to the sole pair of setae of posterior row.Manducatory process with two acuminate distal setae, anterior seta less than 1/2 length of medial seta; apex of coxa I with a rounded anteromedial process; coxae II with 9-12 terminally indented coxal spines on each side, set as an oblique and arc row, central spines slightly longer than the others (Fig. 8D); intercoxal tubercle absent; Chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5.
Chelicera (Figs 7C,8B): almost as long as carapace, 1.71-2.00× as long as broad; five setae and two lyrifissures (exterior condylar lyrifissure and exterior lyrifissure) present on hand, all setae acuminate, ventrobasal setae shorter than others; movable finger with one medial seta.Cheliceral palm has moderate wrinkle on both ventral and dorsal sides.Both fingers well provided with teeth, fixed finger with 12-15 teeth, distal one largest; movable finger with 16-18 retrorse contiguous small teeth; galea completely vestigial (Fig. 8B).Serrula exterior with 17-20 and serrula interior with 14-20 blades.Rallum with eight blades, the distal one longest and recumbent basally, with fine barbules and slightly set apart from the other blades, latter tightly grouped and with long pinnae, some of which are subdivided (Fig. 8C).
Remarks.Lagynochthonius gibbus sp.nov.most closely resembles L. duo sp.nov.due to the presence of intercalary teeth only on the fixed chelal finger, the presence of eight blades on rallum, and similar size (chela length of males 0.73-0.80mm, females 0.79-0.91mm).However, the new species differs from L. duo sp.nov. in the shape of the epistome which is hump-shaped in L. gibbus sp.nov., but triangular in L. duo sp.nov., and in the number of setae on tergites I and II, with four setae on each in L. gibbus sp.nov.compared to two setae on each in L. duo sp.nov.
Cephalothorax (Figs 11D, 12A): carapace nearly subquadrate, 0.97-1.03× as long as broad, strongly constricted basally; posterior region with squamous sculpturing laterally, other area smooth, without furrows; anterior margin smooth, without serrate; epistome small and hump-shaped; four well-developed eyes; with 18 setae arranged s4s: 4: 4: 2: 2, most setae heavy, long and gently curved, anterolateral setae much shorter than others; with two pairs of lyrifissures, first pair situated middle to the setae of ocular row, second pair situated lateral to the sole pair of setae of posterior row.Manducatory process with two acuminate distal setae, anterior seta less than 1/2 length of medial seta; apex of coxa I with a rounded anteromedial process; coxae II with 8-10 terminally indented coxal spines on each side, set as an oblique and arc row, central spines slightly longer than the others (Fig. 12D); intercoxal tubercle absent; Chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5.

Chelicera (Figs 11C, 12B
): almost as long as carapace, 1.63-1.81× as long as broad; five setae and two lyrifissures (exterior condylar lyrifissure and exterior lyrifissure) present on hand, all setae acuminate, ventrobasal setae shorter than others; movable finger with one medial seta.Cheliceral palm has moderate wrinkle on both ventral and dorsal sides.Both fingers well provided with teeth, fixed finger with 9-12 teeth, distal one largest; movable finger with 12-15 retrorse contiguous small teeth; galea completely vestigial (Fig. 12B).Serrula exterior with 16-23 and serrula interior with 14-20 blades.Rallum with eight blades, the distal one longest and recumbent basally, with fine barbules and slightly set apart from the other blades, latter tightly grouped and with long pinnae, some of which are subdivided (Fig. 12C).
Remarks.Lagynochthonius hepingensis sp.nov.most closely resembles L. tonkinensis in the presence of intercalary teeth on both chelal fingers and the presence of four setae on both tergal chaetotaxy I-II.However, it differs by the presence of a hump-shaped epistome and four well-developed eyes, whereas L. tonkinensis has a flat, rounded epistome and spot-like posterior pair of eyes (Beier 1951).
Distribution.China (Guizhou Province).GZ2022080904), all with the same data as the holotype.

Lagynochthonius houi
Etymology.This species is named for Yanmeng Hou, who participated in field work and collected some of the specimens.A noun in apposition.
Cephalothorax (Figs 15D,16A): carapace nearly subquadrate, 0.91-0.97× as long as broad, weakly constricted basally; posterior region with squamous sculpturing laterally, other aera smooth, without furrows; anterior margin smooth, without serrate; epistome small and triangular; four eyes, anterior pair of eyes well-developed, posterior pair with flat lenses; with 18 setae arranged s4s: 4: 4: 2: 2, most setae heavy, long and gently curved, anterolateral setae much shorter than others; with two pairs of lyrifissures, first pair situated middle to the setae of ocular row, second pair situated lateral to the sole pair of setae of posterior row.Manducatory process with two acuminate distal setae, anterior seta less than 1/2 length of medial seta; apex of coxa I with a rounded anteromedial process; coxae II with 9-12 terminally indented coxal spines on each side, set as an oblique and arc row, central spines slightly longer than the others (Fig. 16D); intercoxal tubercle absent; Chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5.
Chelicera (Figs 15C,16B): almost as long as carapace, 1.71-1.88× as long as broad; five setae and three lyrifissures (including an exterior condylar lyrifissure, an exterior lyrifissure and extra lyrifissure (near sub basal setae)) present on hand, all setae acuminate, ventrobasal setae shorter than others; movable finger with one medial seta.Cheliceral palm has moderate wrinkle on both ventral and dorsal sides.Both fingers well provided with teeth, fixed finger with 9-12 teeth, distal one largest; movable finger with 11-13 retrorse contiguous small teeth; galea completely vestigial (Fig. 16B).Serrula exterior with 17-22 and serrula interior with 11-14 blades.Rallum with eight blades, the distal one longest and recumbent basally, with fine barbules and slightly set apart from the other blades, latter tightly grouped and with long pinnae, some of which are subdivided (Fig. 16C).
Pedipalp (Figs 15A, B, E, 16E, 17A, B): trochanter 2.00-2.12,femur 5. 90-6.78, patella 2.44-2.67, chela 6.31-6.75, hand 3.23-3.25× as long as broad; femur 2.45-2.68× as long as patella; movable chelal finger 0.95-1.05× as long as hand and 0.49-0.51× as long as chela.Setae generally long and acuminate.Chelal palm gradually constricted towards fingers, apodeme complex of movable chelal finger strongly sclerotized.Fixed chelal finger and hand with eight trichobothria, movable chelal finger with four trichobothria, ib and isb situated close together, submedially on dorsum of chelal hand; eb, esb and ist forming a straight oblique row at base of fixed chelal finger; it slightly distal to est, situated subdistally; et slightly near to tip of fixed chelal finger, very close to chelal teeth; dx situated distal to et; sb slightly closer to st than to b; b and t situated subdistally, t situated at the same level as it and distal to b; est situated distal to b (Figs 15A, 17A).Fixed chelal finger with sensilla af 1-2 close together, near tip; movable chelal finger with four sensilla: am 1-2 near tip, p 2 slightly distad of sb, p 1 distad of p 2 and very close to chelal teeth (Fig. 17A).Microsetae (chemosensory setae) present on dorsum of chelal hand (Figs 15B, 17B).Both chelal fingers with a row of teeth, spaced regularly along the margin, teeth smaller distally and proximally: fixed finger with 15-19 well-spaced, pointed teeth, and a modified accessory tooth on prolateral-retrolateral face (td, slightly distal to dx); movable finger with seven well-spaced, pointed teeth, plus 10-12 vestigial, rounded and contiguous basal teeth.
Remarks.Lagynochthonius houi sp.nov.differs from all other epigean species of the genus Lagynochthonius from China except L. duo sp.nov.by the following combination of characters: the presence of a triangular epistome and the presence of two setae on tergite I and II (Beier 1951(Beier , 1967;;Hu and Zhang 2012a, b;Zhang and Zhang 2014).
Lagynochthonius houi sp.nov.differs from L. duo sp.nov. in the length of the movable chelal finger which is 0.95-1.05× as long as the hand in males and 0.91 × as long as the hand in female, whereas in L. duo sp.nov. it is 1.11-1.27× as long as the hand in males and 1.11 × as long as hand in female.Additionally, L. houi sp.nov.lacks intercalary tooth on the chelal fingers, whereas the fixed chelal finger posesses intercalary teeth in L. duo sp.nov.
Cephalothorax (Figs 19D,20A): carapace nearly subquadrate, 0.92-0.97× as long as broad, weakly constricted basally; posterior region with squamous sculpturing laterally, other area smooth, without furrows; anterior margin smooth, without serrate; epistome small and hump-shaped; four eyes, anterior pair of eyes well-developed, posterior pair with flat lenses; with 18 setae arranged s4s: 4: 4: 2: 2, most setae heavy, long and gently curved, anterolateral setae much shorter than others; with two pairs of lyrifissures, first pair situated middle to the setae of ocular row, second pair situated lateral to the sole pair of setae of posterior row.Manducatory process with two acuminate distal setae, anterior seta less than 1/2 length of medial seta; apex of coxa I with a rounded anteromedial process; coxae II with 9-11 terminally indented coxal spines on each side, set as an oblique and arc row, central spines slightly longer than the others (Fig. 20D); intercoxal tubercle absent; Chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5.
Chelicera (Figs 19C,20B): almost as long as carapace, 1.81-1.93× as long as broad; five setae and three lyrifissures (including an exterior condylar lyrifissure, an exterior lyrifissure and extra lyrifissure (near sub basal setae)) present on hand, all setae acuminate, ventrobasal setae shorter than others; movable finger with one medial seta.Cheliceral palm has moderate wrinkle on both ventral and dorsal sides.Both fingers well provided with teeth, fixed finger with 14-18 teeth, distal one largest; movable finger with 16-18 retrorse contiguous small teeth; galea completely vestigial (Fig. 20B).Serrula exterior with 19-20 and serrula interior with 10-12 blades.Rallum with seven blades, the distal one longest and recumbent basally, with fine barbules and slightly set apart from the other blades, latter tightly grouped and with long pinnae, some of which are subdivided (Fig. 20C).
Pedipalp (Figs 19A,B,E,20E,21A,B): trochanter 1. 88-2.14, femur 6.50-6.75, patella 2.22-2.50, chela 6.80-7.89, hand 3.20-3.67× as long as broad; femur 2.57-2.65 × as long as patella; movable chelal finger 1.15-1.19× as long as hand and 0.53-0.56× as long as chela.Setae generally long and acuminate.Chelal palm gradually constricted towards fingers, apodeme complex of movable chelal finger strongly sclerotized.Fixed chelal finger and hand with eight trichobothria, movable chelal finger with four trichobothria, ib and isb situated close together, submedially on dorsum of chelal hand; eb, esb and ist at base of fixed chelal finger; esb and eb at almost the same level and ist slightly distal to esb; it slightly distal to est, situated subdistally; et slightly near to tip of fixed chelal finger, very close to chelal teeth; dx situated distal to et; sb slightly closer to st than to b; b and t situated subdistally, t situated at the same level as it and distal to b; est situated distal to b and close to it (Figs 19A,21A).Fixed chelal finger with sensilla af 1-2 close together, near tip; movable chelal finger with four sensilla: am 1-2 near tip, p 2 slightly distad of sb, p 1 proximad of sb and very close to chelal teeth (Fig. 21A).Microsetae (chemosensory setae) present on dorsum of chelal hand (Figs 19B,21B).Both chelal fingers with a row of teeth, spaced regularly along the margin, teeth smaller distally and proximally: fixed finger with 18 or 19 well-spaced, pointed teeth, and a modified accessory tooth on prolateral-retrolateral face (td, slightly distal to dx); movable finger with six wellspaced, pointed teeth, plus 8-10 vestigial, rounded and contiguous basal teeth.
Remarks.Lagynochthonius sanhuaensis sp.nov.most closely resembles L. niger in the absence of intercalary teeth and the presence of four setae on tergites I and II, but differs from it in several characters.First, the new species has a shorter (0.68-0.73 mm compared to 0.75-0.93mm in L. niger) and thinner chela (6.80-7.89× as long as broad compared to 5.17-6.25 × as long as broad in L. niger) in males.Second, the shape of the epistome is hump-shaped in L. sanhuaensis sp.nov., whereas it is triangular in L. niger.Third, the rallum has seven blades in L. sanhuaensis sp.nov., whereas it has eight blades in L. niger (Hu and Zhang 2012a).

Figure 5 .
Figure 5. Type locality of Lagynochthonius duo sp.nov.A stone step road B selected deciduous layers C beside the stream D areas where L. duo sp.nov.specimens were collected.