Korean dragon pseudoscorpions revisited: a taxonomic review of Allochthonius (Pseudoscorpiones: Pseudotyrannochthoniidae) Chamberlin, 1929 with three new species

Kyung-Hoon Jeong; Danilo Harms; Sora Kim

doi:10.7717/peerj.21332

. 2026 Jun 2;14:e21332. doi: 10.7717/peerj.21332

Korean dragon pseudoscorpions revisited: a taxonomic review of Allochthonius (Pseudoscorpiones: Pseudotyrannochthoniidae) Chamberlin, 1929 with three new species

Kyung-Hoon Jeong ^1,², Danilo Harms ^2,^3,⁴, Sora Kim ^5,^6,^✉

Editor: Viktor Brygadyrenko

PMCID: PMC13239490 PMID: 42254670

Abstract

Allochthonius (Pseudoscorpiones: Pseudotyrannochthoniidae) is a genus widely distributed throughout East Asia. In Korea, only three species in this genus have been recorded to date: Allochthonius buanensis Lee, 1982; Allochthonius coreanus Morikawa, 1970; and Allochthonius opticus Ellingsen, 1907. Here, we review the Korean fauna of Allochthonius and describe three new species for the country: Allochthonius jungsuni sp. nov., Allochthonius maximus sp. nov., and Allochthonius rufimanus sp. nov. We also exclude Allochthonius opticus –a species originally described from Japan—from the country record and redescribe two Korean recorded species, Allochthonius buanensis and Allochthonius coreanus. Following up on our previous taxonomic work that elevated several subspecies of Japanese pseudotyrannochthoniids originally described by Kuniyasu Morikawa to species level, we elevate eight former subspecies to full species rank: A. ishikawai deciclavatus Morikawa, 1956 = A. deciclavatus Morikawa, 1956, stat. nov., A. ishikawai ishikawai Morikawa, 1954 = A. ishikawai Morikawa, 1954, A. ishikawai kyushuensis Morikawa, 1960 = A. kyushuensis Morikawa, 1960, stat. nov., A. ishikawai shiragatakiensis Morikawa, 1954 = A. shiragatakiensis Morikawa, 1954, stat. nov., A. ishikawai uenoi Morikawa, 1956 = A. uenoi Morikawa, 1956, stat. nov., and A. ishikawai uyamadensis Morikawa, 1954 = A. uyamadensis Morikawa, 1954, stat. nov.; A. opticus opticus Ellingsen, 1907 = A. opticus Ellingsen, 1907, and A. opticus troglophilus Morikawa, 1956 = A. troglophilus Morikawa, 1956, stat. nov.. This elevates the total number of Allochthonius species from 40 to 43, of which five species are presently known from the Korean Peninsula.

Keywords: DNA barcoding, Republic of Korea, Pseudoscorpiones, Subspecies, Systematics, Taxonomy

Introduction

The pseudoscorpion family Pseudotyrannochthoniidae Beier, 1932 represents one of the most basal lineages among the 26 recognized families of Pseudoscorpiones (Benavides et al., 2019; World Pseudoscorpiones Catalog, 2022). Members of this family are commonly referred to as “dragon pseudoscorpions” due to their markedly enlarged chelicerae (Harms et al., 2024). Pseudotyrannochthoniidae is diagnosed by the presence of trichobothria ib and isb positioned at the base of the fixed chelal finger, in combination with coxal spines restricted to coxa I (Harms & Harvey, 2013; Hou & Zhang, 2024). Pseudotyrannochthoniidae currently comprises seven genera and 108 species: Afrochthonius Beier, 1930; Allochthonius Chamberlin, 1929; Centrochthonius Beier, 1931; Karrichthonius Harms et al., 2025; Pseudotyrannochthonius Beier, 1930; Selachochthonius Chamberlin, 1929; and Spelaeochthonius Morikawa, 1954; World Pseudoscorpiones Catalog, 2022; Lin et al., 2025). Three of these genera—Allochthonius (China, Japan, Russia, the Republic of Korea, Taiwan), Centrochthonius (China, Kyrgyzstan, Nepal), and Spelaeochthonius (China, Japan, the Republic of Korea)—are distributed across Asia. Species within these genera typically exhibit small distribution ranges (Harms et al., 2024; Hou & Zhang, 2024) and are most frequently encountered in the leaf litter of mesic forest ecosystems, although numerous species are troglobitic and occur exclusively in cave habitats (e.g., You et al., 2022; Jeong et al., 2025).

Dated molecular phylogenetic data indicates that the genus Allochthonius (Chamberlin, 1929) originated in Asia during the Early Cretaceous (Harms et al., 2024). There is one fossil species dating back to the Eocene of Europe (33.7–33.9 Ma) (Schwarze et al., 2021), but all 40 extant species are distributed in eastern Asia: 15 species in China, 14 in Japan, seven in Taiwan, three in the Republic of Korea, and one in Russia (World Pseudoscorpiones Catalog, 2022; Lin et al., 2025). Species of Allochthonius can be diagnosed based on variable numbers of carapacal setae (18–28; Sakayori, 2000; Viana & Ferreira, 2021; You et al., 2022) and the presence of “fan-shaped” or “spray-shaped” coxal spines (Chamberlin, 1929; Morikawa, 1960; Morikawa, 1962; Harvey & Harms, 2022; Hou & Zhang, 2024). To date, three species of Allochthonius have been formally recorded in the Republic of Korea: the “widespread” morphospecies Allochthonius buanensis Lee, 1982 (Type locality: Buan, Jeollabuk-do), Allochthonius coreanus (Type locality: Sinryeong-gul Cave in Gangwon-do), and Allochthonius opticus; a species originally described from Okayama, Japan but also recorded from Korea by Lee & Seo, 1995 (Morikawa, 1970; Lee, 1982; Lee & Seo, 1995). However, a recent barcoding study has indicated that the diversity of Allochthonius in Korea is clearly much higher and some of the most common species (e.g., Allochthonius buanensis Lee, 1982) clearly represent species complexes in molecular phylogenies or DNA barcoding studies (Ohira et al., 2018).

Despite being the most commonly collected pseudoscorpion genus in the Republic of Korea (Lee & Seo, 1995; Hong, 1996), the diversity of Allochthonius in this region has not been critically reassessed since the 1990s. All previous Korean records were based on limited morphological examinations, and the type materials used in these studies have since been lost (Y. Hong, 2023, pers. comm.), rendering direct comparisons with newly collected material impossible. Recent molecular and taxonomic studies on pseudotyrannochthoniids across East Asia have consistently demonstrated that species in this family exhibit narrow-range endemism and low dispersal capacity, and that broad morphospecies concepts often mask considerable cryptic diversity (Ohira et al., 2018; Harms et al., 2024; Harms et al., 2025; Lin et al., 2025). We will test the hypothesis that the species richness of Allochthonius on the Korean Peninsula has been substantially underestimated due to cryptic speciation and narrow-range endemism. To address this, we employ an integrative taxonomic framework combining detailed morphological examination using stereomicroscopy and scanning electron microscopy (SEM) with COI DNA barcoding data, thereby providing two independent lines of evidence for species delimitation.

Herein, we review the Korean fauna of Allochthonius and describe three new epigean species from leaf litter habitats. We also correct a previous misidentification and remove Allochthonius opticus from the Korean record and re-describe both A. buanensis and A. coreanus. Following up on previous work that elevated several subspecies of Japanese pseudotyrannochthoniids to full species rank (You et al., 2022), we complete this work and elevate eight previously recognized subspecies of Allochthonius to full species rank, this updating species concepts in light of recent taxonomic and molecular work on this family.

Materials and methods

Morphological identification

The specimens used for this study are deposited in the following institutions: Museum of Nature Hamburg, Hamburg, Germany (ZMH), National Institute for Biological Resources, Incheon, Republic of Korea (NIBR), and Jeonbuk National University, Jeonju, Republic of Korea (JBNU). All specimens are stored in 100% ethanol.

All specimens in this study were examined using a Leica Z16 APO stereomicroscope. Habitus images were captured using a Leica Z16 APO stereomicroscope and Dhyana 400 DC (4M) sCMOS camera (TUCSEN, Fuzhou, China) and using Mosaic Analysis Software 2.4. Images of appendages were captured using a Leica M205A stereomicroscope and a Leica DMC4500 digital camera, using Leica Application Suite X (LASX) ver. 3.0.1. Appendages were drawn using Adobe Illustrator 2026 (Adobe Inc.). Scanning electron micrographs (SEM) were pictured using a Hitachi TM4000Plus scanning electron micrograph system.

Measurements and terminology follow the following studies (Chamberlin, 1931; Harvey, 1991; Judson, 2007; Kolesnikov, Przhiboro & Turbanov, 2023). Abbreviations for chelal trichobothria: b–basal, sb–subbasal, st–subterminal, t–terminal, ib–internal basal, isb–internal subbasal, eb–external basal, esb–external subbasal, it–internal terminal, ist –internal subterminal, et–external terminal, est–external subterminal, xs–duplex trichobothria. Abbreviations for carapacal setae: A1–1st anterior seta, A2–2nd anterior seta, A3–3rd anterior seta, A4–4th anterior seta, A5–5th anterior seta, Ol–lateral ocular seta, Om1–1st medial ocular seta, Om2–2nd medial ocular seta, Ml–medialateral seta, Mm1–1st medial seta, Mm2–2nd medial seta, Il–intermedialateral seta, Pl–posterolateral seta, Pm–posteromedial seta.

Molecular analyses

To generate an integrated taxonomic hypothesis, all five Korean species of Allochthonius are recognized below were also barcoded using a 597bp fragment of cytochrome c oxidase subunit I (COI). The species are: Allochthonius buanensis (Lee, 1982 GenBank No. OR290020), Allochthonius coreanus (Morikawa, 1970 OR290038), Allochthonius jungsuni sp. nov. (PX533168), Allochthonius maximus sp. nov. (PX921017), and Allochthonius rufimanus sp. nov. (PX533173). A. buanensis and A. coreanus used in this study were sequenced by Harms et al. (2024), which are sampled in their type localities. DNA was extracted by grinding two or three legs detached from each specimen, using Dneasy Blood & Tissue Kit (QIAGEN, Valencia, CA) and LaboPss^Tm DNA purification Kit (Cosmo Genetech Co. Ltd., Seoul, Republic of Korea) following the manufacturer’s protocol. PCR amplification was conducted using the primer set LCO1490 (5′-GGTCAACAAATCATCATAAAGATATTGG-3′) (Folmer et al., 1994) and HCOoutout (5′-GTAAATATATGRT GDGCTC-3′) (Prendini, Weygoldt & Wheeler, 2005) and under the following conditions: initial denaturation at 94 °C for 2min, followed by 40 cycles of denaturation at 95 °C for 30 s, annealing at 40–45 °C for 30 s, extension at 72 °C for 1min, and a final extension at 72 °C for 5min. DNA amplification utilized AccuPower PCR Premix (Bioneer, Daejeon, Republic of Korea) and sequencing was done by Macrogen, Inc. (Geumcheon-Gu, Seoul, Republic of Korea). Interspecific genetic distance was calculated using MEGA 11.0 and the Kimura 2-parameter model (Tamura, Stecher & Kumar, 2021). Sequences generated in this study are deposited in GenBank (Table 1).

Table 1. Interspecific genetic divergences within all Korean Allochthonius species.

	A. buanensis OR290020	A. coreanus OR290038	A. jungsuni sp. nov. PX533168	A. maximus sp. nov. PX921017
A. buanensis OR290020
A. coreanus OR290038	16.2%
A. jungsuni sp. nov. PX533168	13.2%	16.0%
A. maximus sp. nov. PX921017	20.3%	16.2%	19.0%
A. rufimanus sp. nov. PX533173	17.9%	17.9%	17%	24.3%

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Nomenclatural acts

The electronic version of this article in Portable Document Format (PDF) will represent a published work according to the International Commission on Zoological Nomenclature (ICZN), and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix http://zoobank.org/. The LSID for this publication is: urn:lsid:zoobank.org:pub:A53E1EB1-DE99-45D8-B92B-E538649EEB13. The online version of this work is archived and available from the following digital repositories: PeerJ, PubMed Central SCIE and CLOCKSS.

Result

Taxonomy

Family Pseudotyrannochthoniidae Beier, 1932

Genus Allochthonius Chamberlin, 1929

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Type species. Chthonius opticus Ellingsen, 1907, by original designation.

Allochthonius buanensis Lee, 1982

Allochthonius buanensis. Lee, 1982: 76-79, figs. 1a-c, 2a-k, table 1; Bang, 1984: 11-15, table 4–5, plate 1-2, 3-2, 3-4, 5-2, 5-4, 7-2, 9-2, 11-2; Hong, 1996: 19-23.

Allochthonius (Allochthonius) buanensis. Lee & Seo, 1995: 456-459, figs. 1a-d, 2a, 3a, table 1; Hong, Kim & Lee, 1996: 174-175; Ohira et al., 2018: 400, 402, 404-405, fig. 3.

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Material examined. KOREA 2♀, 3♂: Jeollabukdo-Province, Buan-gun, Byeonsan-myeon, Junggye-ri: 35°38′6.22″N, 126°34′28.29″E; 31 May 2024; KH Jeong leg; JBNU-KH129JB (JBNU).

Diagnosis. This species is most similar to Allochthonius exornatus Gao and Zhang, 2013 from China by the number of marginal teeth on the fixed chelal finger (16–18 in A. buanensis, 18 in A. exornatus), six coxal spines, and six setae on the cheliceral palm. Both species can be distinguished by the number of setae on the carapace (10-4: 24 in A. buanensis vs 10-4: 26 in A. exornatus), and the number of marginal teeth on the movable chelal finger (13–17 in A. buanensis vs 5–7 in A. exornatus).

Description.

Female, adult (n = 2) (Figs. 1A–1B)

(A) Female adult, dorsal view; (B) female adult, ventral view; (C) male adult, dorsal view; (D) male adult, ventral view.

Colour. Body light-brown; pedipalps weakly sclerotized; tip of appendages red.

Cephalothorax (Figs. 2A–2C, 3A). Carapace 0.84–0.85 times longer than broad; subquadrate; four distinct eyes; epistome absent; 24 setae on the carapace; 10 setae on the anterior margin (A1, A2, A3, A4, A5), a pair of setae on the lateral margin (Ol), four setae pairs on the medial margin (Om2, Ml, Mm2, Il), two pairs of setae on the posterior margin (Pl, Pm). Two acuminate setae on the manducatory process, maxilla with three setae; coxal chaetotaxy 3–4: 5: 5–6: 6; coxal spines with seven long blades; bisetose intercoxal tubercle present between coxa III and IV.

(A) Carapace, dorsal view; (B) coxal spines; (C) coxa; (D) right chelicera, dorsal view; (E) Left pedipalp, dorsal view; (F) left chela, lateral view.

(A) Coxal spines; (B) right chelicera, dorsal view; (C) serrula exterior; (D) rallum; (E) right pedipalp, dorsal view; (F) left chela, lateral view.

Chelicera (Figs. 2D, 3B–3D). Palm smooth; five setae on the dorsal of palm, one seta on the ventral of palm, one seta on the movable finger; 5–6 small marginal teeth on the fixed finger, 10–11 marginal teeth on the movable finger; rallum with ten blades; serrula exterior with 16–17 blades.

Pedipalp (Figs. 2E–2F, 3E–3F). Trochanter 1.35–1.37 times, femur 3.74–3.86 times, patella 1.92–1.95 times, chela 3.8–3.89 times, hand 1.46–1.52 times longer than broad, movable finger 1.56–1.6 times longer than hand. Fixed finger with eight trichobothria, movable finger with four trichobothria; ib and isb positioned basally on the dorsum of the fixed finger; eb, ist, and esb grouped together, ist distinctly closer to esb than eb, ist located on the middle of the eb and esb; it and est located on the middle of the fixed finger, slightly closer to tip; et located next to xs, xs terminally positioned on the fixed finger; sb, b, and t separately located from st; st basally positioned on the movable finger. Fixed finger with 17–18, movable finger with 15–16 marginal teeth.

Legs. Leg I: trochanter 1.44 times, femur 3.52–3.68 times, patella 2.97–3.06 times, tibia 2.7–2.71 times, tarsus 7.56–7.61 times longer than broad. Leg IV: trochanter 1.26–1.31 times, femur+patella 3.01–3.03 times, tibia 4.11–4.26 times, metatarsus 2.4–2.7 times, tarsus 6.61–7.16 times longer than broad; arolium undivided; pseudotactile setae basally present on leg IV metatarsus and tarsus.

Abdomen. Pleural membrane granulate; tergites undivided; tergal chaetotaaxy 4: 4: 6: 6–8: 6–7: 6–8: 8–10: 8–10:8–9: 6–7: 4: 0: 0; sternites III–IV divided, sternite V partly divided; sternal chaetotaxy 5–8: 16–18: 13–14: 10–14: 12–14: 10–14: 12–14: 10–14: 8–9: 4: 2.

Dimensions (in mm). Body length 1.45–1.51. Pedipalp: trochanter 0.17–0.18/0.13, femur 0.53–55/0.14–15, patella 0.26–0.27/0.14, chela (with pedicel) 1.01–1.05/0.27, movable finger 0.62–0.64, hand 0.41–0.49/0.27. Chelicera: total 0.41–0.42/0.21, movable finger 0.18–0.2, hand 0.22–0.23/0.21. Carapace 0.41–0.42/0.48–0.49; anterior eye 0.03–0.04; posterior eye 0.03–0.05. Leg I: trochanter 0.20/0.14, femur 0.39–0.40/0.11, patella 0.25/0.08–0.09, tibia 0.19–0.2/0.07, tarsus 0.42–0.43/0.06. Leg IV: trochanter 0.18–0.19/0.14–0.15, femur+patella 0.52–0.53/0.17–0.18, tibia 0.37–0.38/0.09, metatarsus 0.14–0.17/0.06, tarsus 0.27/0.04.

Male, adult (n = 3) (Figs. 1C–1D)

Cephalothorax. Carapace 0.81–0.93 times longer than broad; with 24 setae; 10 setae on the anterior margin, and four setae on the posterior margin. Coxal chaetotaxy 3–4: 5–6: 5–6: 6–7; coxal spines with seven blades.

Pedipalp. Trochanter 1.38–1.51 times, femur 4.47–5.05 times, patella 1.89–2.19 times, chela 4.66–4.82 times, hand 1.77–1.8 times longer than broad, movable finger 1.6–1.72 times longer than the hand. Fixed finger with 16–18, movable finger with 15–17 marginal teeth.

Legs. Leg I: trochanter 1.12–1.27 times, femur 3.45–4.97 times, patella 2.59–3.03 times, tibia 3.1–3.76 times, tarsus 7.45–8.22 times longer than broad. Leg IV: trochanter 1.19 times, femur+patella 2.54–3.79 times, tibia 4.57–5.6 times, metatarsus 2.6–2.7 times, tarsus 8.73–9.5 times longer than broad.

Abdomen. Tergal chaetotaxy 4: 4: 6: 7: 8: 9: 9: 9: 6: 4: 0: 0; sternal chaetotaxy 7: 28: 12: 15: 15: 16: 14: 10: 2–4: 2.

Dimensions (in mm). Body length 1.58–1.61. Pedipalp: trochanter 0.16–0.17/0.11–0.12, femur 0.51–0.53/0.11, patella 0.20–0.21/0.10, chela (with pedicel) 0.81–0.85/0.17–0.18, movable finger 0.52, hand 0.29–0.33/0.17–0.18. Chelicera: total 0.33–0.37/0.17–0.18, movable finger 0.19, hand 0.14–0.18/0.17–0.18. Carapace 0.34–0.42/0.42–0.45; anterior eye 0.04–0.05; posterior eye 0.05. Leg I: trochanter 0.11–0.12/0.09, femur 0.25–0.30/0.06–0.07, patella 0.14–0.19/0.05–0.06, tibia 0.15–0.17/0.04–0.05, tarsus 0.27–0.32/0.04. Leg IV: trochanter 0.13/0.11, femur+patella 0.44–0.48/0.13–0.17, tibia 0.34–0.46/0.07–0.08, metatarsus 0.14–0.15/0.05–0.06, tarsus 0.34–0.36/0.04.

Sequence data. GenBank Accession No. OR290020. A. buanensis differs from other Korean species by 13.2% (A. jungsuni sp. nov.) to 20.3% (A. maximus sp. nov.) pairwise divergences in the CO1 data respectively.

Allochthonius coreanus Morikawa, 1970

Allochthonius (Allochthonius) opticus coreanus. Morikawa, 1970: 141-143, , figs. 1, 2a; Lee & Seo, 1995: 460-464, figs. 2b, 3c, 5a-d, 6; Hong, Kim & Lee, 1996: 175.

Allochthonius coreanus. Bang, 1984: 6-8, table 2-3, plate 1-1, 3-1, 3-3, 5-1, 5-3, 7-1, 9-1, 11-1; Hong & Kim, 1993: 2; Hong, 1996: 23-24.

Allochthonius (Allochthonius) coreanus. Ohira et al., 2018: 400.

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Materials examined. KOREA 1♀, 2♂: Gangwondo-Province, Jeongseon-gun, Bukpyeong-myeon, Najeon-ri, 256-1; 37°26′21.4″N 128°37′30.7″E; 23 April 2020; YJ Choi and UJ Byeon leg; JBNU-KH1086GW (JBNU). KOREA 1♀, 3♂: Gyeonggido-Province, Yangpyeong-gun, Yangdong-myeon, Hwanggeo-gil, 262-10; 37°27′39.60″N, 127°43′5.68″E; 14 May 2022; KH Jeong leg; ZMH-A@@ (ZMH; 1♀, 1♂), JBNU-KH028GG (JBNU, 2♂).

Diagnosis. This species is most similar to Allochthonius fanjingshan Gao, Zhang and Zhang, 2016 in the following characteristics: number of carapacal setae (10-4: 28 in both species) and six setae on the cheliceral palm. It can be distinguished from A. fanjingshan by the following characteristics: number of coxal spines (seven in A. coreanus vs nine in A. fanjingshan), the number of marginal teeth on the chelal fingers (24–30 in fixed finger, 27–31 in movable finger of A. coreanus vs 15–16 in fixed finger, 20–21 in movable finger of A. fanjingshan).

Description.

Female, adult (n = 2) (Figs. 4A–4B)

Colour. Body dark-brown; pedipalps strongly sclerotized; chela black.

Cephalothorax (Figs. 5A–5C, 6A). Carapace 0.88–0.96 times longer than broad; rectangular; four distinct eyes; epistome absent; 28 setae on the carapace; five setae pairs on the anterior margin (A1, A2, A3, A4, A5), a pair of setae on the lateral margin (Ol), six setae pairs on the medial margin (Om1, Om2, Ml, Mm1, Mm2, Il), and two pairs of setae on the posterior margin (Pl, Pm). Two acuminate setae on the manducatory process, maxilla with three setae; coxal chaetotaxy 3–4: 3–5: 6–7: 5–7; coxal spines with seven long blades; bisetose intercoxal tubercle present between coxa III and IV.

(A) Coxal spines; (B) left chelicera, dorsal view; (C) serrula exterior; (D) rallum; (E) left pedipalp, dorsal view; (F) right chela, lateral view.

Chelicera (Figs. 5D, 6B–6D). Palm smooth; palm with six setae, one seta on the movable finger; 3–5 large marginal teeth on the fixed finger, 11–14 small marginal teeth on the movable finger; rallum with eight blades; serrula exterior with 18–19 blades.

Pedipalp (Figs. 5E–5F, 6E–6F). Trochanter 1.32–1.44 times, femur 4.5–4.93 times, patella 1.69–2.2 times, chela 4.14–4.65 times, hand 1.83–1.88 times longer than broad, movable finger 1.27–1.47 times longer than the hand. Fixed finger with 28–30, movable finger with 27–30 small and dentate marginal teeth. Fixed finger with eight trichobothria, movable finger with four trichobothria; ib and isb positioned basally on the dorsum of the fixed finger; eb, ist, and esb grouped together, ist located distinctly closer to esb than eb; it and est located on the middle of the fixed finger, closer to tip; et located next to xs, xs positioned terminally on the fixed finger; sb, b, and t separately located from st; st basally positioned on the movable finger.

Legs. Leg I: trochanter 1.32–1.47 times, femur 3.82–5.78 times, patella 2.76–3.78 times, tibia 2.87–3.63 times, tarsus 7.17–8 times longer than broad. Leg IV: trochanter 1.33–1.78 times, femur+patella 2.66–2.9 times, tibia 3.31–4.92 times, metatarsus 2.85–3.3 times, tarsus 6.44–9.5 times longer than broad; arolium undivided; pseudotactile setae basally present on leg IV metatarsus and tarsus.

Abdomen. Pleural membrane granulate; tergites undivided; tergal chaetotaxy 4: 6–7: 7–8: 8–9: 8–9: 10–11: 10–12: 11: 11: 10: 0: 0; sternites III–IV divided, sternite V partly divided; sternal chaetotaxy 10–12: 18–22: 16–18: 14: 14: 10–14: 10–11: 9–12: 8–11: 2: 2.

Dimensions (in mm). Body length 2.01–2.43. Pedipalp: trochanter 0.24–0.29/0.17–0.22, femur 0.83–0.9/0.17–0.2, patella 0.32–0.44/0.14–0.2, chela (with pedicel) 1.22–1.45/0.26–0.35, movable finger 0.73–0.81, hand 0.49–0.64/0.26–0.35. Chelicera: total 0.51–0.6/0.24–0.3, movable finger 0.26–0.32, hand 0.25–0.28/0.24–0.3. Carapace 0.51–0.58/0.53–0.66; anterior eye 0.06; posterior eye 0.05–0.07. Leg I: trochanter 0.19–0.25/0.14–0.17, femur 0.42–0.45/0.08–0.11, patella 0.25–0.34/0.09, tibia 0.22–0.29/0.08, tarsus 0.42–0.56/0.06–0.07. Leg IV: trochanter 0.30–0.32/0.18–0.2, femur+patella 0.60–0.87/0.23–0.3, tibia 0.48–0.64/0.13–0.15, metatarsus 0.23–0.33/0.08–0.1, tarsus 0.34–0.57/0.05–0.06.

Male, adult (n = 5) (Figs. 4C–4D)

Cephalothorax. Carapace 0.92–0.99 times longer than broad and with 28 setae; 10 setae on the anterior margin, and four setae on the posterior margin. Coxal chaetotaxy 4: 4–5: 6–8: 5–8. Coxal spines with eight blades.

Pedipalp. Trochanter 1.35–1.44 times, femur 4.7–4.94 times, patella 1.69–2.05 times, chela 4.5–4.65 times, hand 1.88–1.97 times longer than broad, movable finger 1.29–1.47 times longer than the hand. Fixed finger with 24–27, movable finger with 28–31 marginal teeth.

Legs. Leg I: trochanter 1.28–1.32 times, femur 3.64–5.78 times, patella 2.76–3.27 times, tibia 2.87–3.38 times, tarsus 7.17–8.5 times longer than broad. Leg IV: trochanter 1.33–1.71 times, femur+patella 2.66–3.12 times, tibia 3.31–3.69 times, metatarsus 2.85–3.11 times, tarsus 6.44–8.33 times longer than broad.

Abdomen. Tergal chaetotaxy 4: 6–8: 8–9: 8–9: 8–9: 10–12: 10–12: 9–11: 10–11: 10: 0: 0; sternal chaetotaxy 10–12: 36–40: 16–20: 14–18: 15–16: 10–12: 10–11: 9–10: 8–10: 2–4: 2.

Dimensions (in mm). Body length 1.83–2.41. Pedipalp: trochanter 0.24–0.27/0.17–0.2, femur 0.83–0.94/0.17–0.2, patella 0.32–0.43/0.19–0.21, chela (with pedicel) 1.22–1.44/0.26–0.32, movable finger 0.73–0.81, hand 0.5–0.63/0.26–0.32. Chelicera: total 0.51–0.56/0.24–0.26, movable finger 0.26–0.29, hand 0.25–0.27/0.24–0.26. Carapace 0.50–0.56/0.50–0.61; anterior eye 0.05–0.06; posterior eye 0.04–0.06. Leg I: trochanter 0.19–0.23/0.14–0.18, femur 0.4–0.45/0.08–0.11, patella 0.25–0.36/0.09–0.11, tibia 0.22–0.27/0.08, tarsus 0.42–0.51/0.06. Leg IV: trochanter 0.20–0.29/0.15–0.17, femur+patella 0.61–0.81/0.23–0.26, tibia 0.48/0.13–0.15, metatarsus 0.23–0.28/0.08–0.09, tarsus 0.34–0.5/0.05–0.06.

Sequence data. GenBank Accession No. OR290038. A. coreanus differs from the other Korean species by 16% (A. jungsuni sp. nov.) to 17.9% (A. rufimanus sp. nov.) pairwise divergence in the CO1 data respectively.

Allochthonius jungsuni Jeong and Harms sp. nov.

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LSID: urn:lsid:zoobank.org:act:EA291957-FD99-4772-8DD1-C7E566C242D8

Type material. Holotype: KOREA ♀: Gyeongsangnamdo-Province, Geoje-si, Dongbu-myeon, Gojejungang-ro, 325; 34°46′59.54″N, 128°37′33.06″E; 18 April 2024; KH Jeong and Y Cha leg; NIBRIV0000932089 (NIBR). Paratypes 3♂; the same data as the holotype; NIBRIV0000932089 (NIBR; 1♂), JBNU-KH107GN-A (JBNU, 2♂).

Etymology. The specific epithet is dedicated to Dr. Jung-Sun Yoo in recognition of his sincere support, which substantially contributed to the first author’s research in arachnology.

Diagnosis. This species differs from other congeners by the number of coxal spines. Whereas species of Allochthonius typically possess fewer than ten coxal spines, this species has 12–13 spines on coxa I. This species is most similar to Allochthonius borealis Sato, 1984 and shares the same number of carapacal setae (10-4: 26 in both species) and marginal teeth on the fixed chelal finger (18–20 in A. borealis, 19 in A. jungsuni sp. nov.). Both species can easily be distinguished by the number of marginal teeth on the movable chelal finger (8–9 in A. borealis vs 28 in A. jungsuni sp. nov.) and the number of setae on the cheliceral palm (5 in A. borealis vs 7 in A. jungsuni sp. nov.).

Description.

Holotype, female, adult (Figs. 7A–7B)

Colour. Body brownish-grey; pedipalp strongly sclerotized; chelal palm and pedipalpal patella black; chelal finger red.

Cephalothorax (Figs. 8A–8C, 9A). Carapace 0.97 times longer than broad; rectangular; four distinct eyes; epistome absent; 26 setae on the carapace; five setae pairs on the anterior margin (A1, A2, A3, A4, A5), a pair of setae on the lateral margin (Ol), five pairs of setae on the medial margin (Om2, Ml, Mm1, Mm2, Il), two setae pairs on the posterior margin (Pl, Pm). Two acuminate setae on the manducatory process, maxilla with three setae; coxal chaetotaxy 4: 5: 7: 8; coxal spines with 13 long blades; bisetose intercoxal tubercle present between coxa III and IV.

(A) Carapace, dorsal view; (B) coxal spines; (C) coxa; (D) right chelicera, dorsal view; (E) right pedipalp, dorsal view; (F) right chela, lateral view.

(A) Coxal spines; (B) left chelicera, dorsal view; (C) serrula exterior; (D) rallum; (E) left pedipalp, dorsal view; (F) left chela, lateral view.

Chelicera (Figs. 8D, 9B–9D). Palm smooth and with seven setae, one seta on the movable finger; five marginal teeth on the fixed finger, two large teeth positioned basally on the fixed finger; eight small marginal teeth on the movable finger; rallum with eight blades; serrula exterior with 20 blades.

Pedipalp (Figs. 8E–8F, 9E–9F). Trochanter 1.44 times, femur 5.57 times, patella 2 times, chela 4.5 times, hand 2.36 times longer than broad, movable finger 0.91 times longer than hand. Fingers strongly curved. Fixed finger with eight trichobothria, movable finger with four trichobothria; isb and ib basally positioned on the dorsum of the fixed finger; eb, ist, and esb grouped together, ist positioned distinctly closer to esb than eb; est and it positioned on the middle of the fixed finger, located closer to tip than the basal of the fixed finger; et positioned next to xs; xs located terminally on the fixed finger; sb, b, and t positioned apart from st; st position basally on the movable finger. Fixed finger with 19, movable finger with 28 marginal teeth; strong and large marginal teeth on the fixed finger, small and undeveloped teeth on the fixed finger.

Legs. Leg I: trochanter 1.29 times, femur 5.44 times, patella 3.88 times, tibia 4.04 times, tarsus 7.81 times longer than broad. Leg IV: trochanter 1.73 times, femur+patella 4.06 times, tibia 5.14 times, metatarsus 3.5 times, tarsus 10.33 times longer than broad.

Abdomen. Tergites undivided; tergal chaetotaxy 4: 6: 7: 9: 10: 10: 10: 11: 8: 6: 0: 0; sternite III partly divided, sternite IV divided; sternal chaetotaxy 10: 28: 18: 15: 14: 14: 16: 12: 10: 2: 2.

Dimensions (in mm). Body length 2.82. Pedipalp: trochanter 0.26/0.18, femur 1.05/0.19, patella 0.45/0.22, chela (with pedicel) 1.68/0.37, movable finger 0.8, hand 0.88/0.37. Chelicera: total 0.59/0.28, movable finger 0.34, hand 0.25/0.28. Carapace 0.69/0.71; anterior eye 0.07; posterior eye 0.06. Leg I: trochanter 0.23/0.18, femur 0.56/0.1, patella 0.39/0.1, tibia 0.3/0.07, tarsus 0.52/0.07. Leg IV: trochanter 0.35/0.2, femur+patella 0.95/0.23, tibia 0.63/0.12, metatarsus 0.29/0.08, tarsus 0.56/0.05.

Paratypes, male, adult (n = 3) (Figs. 7C–7D)

Cephalothorax. Carapace 1.03–1.14 times longer than broad and with 26 setae; 10 setae on the anterior margin, four setae on the posterior margin. Coxal chaetotaxy 3–4: 4–6: 5–7: 7–8; coxa I with 12–13 short blades.

Pedipalp. Trochanter 1.4–1.44 times, femur 4.92–5.79 times, patella 2.08–2.23 times, chela 5.49–5.56 times, hand 2.4–2.64 times longer than broad, movable finger 1.08–1.31 times longer than the hand. Movable finger with 16–19, fixed finger 27–30 with marginal teeth.

Legs. Leg I: trochanter 1.26–1.39 times, femur 4.01–5.22 times, patella 3.71–3.84 times, tibia 4–4.93 times, tarsus 8.73–9.61 times longer than broad. Leg IV: trochanter 1.61–1.72 times, femur+patella 3.71–3.8 times, tibia 5.68–5.03 times, metatarsus 3.85–3.87 times, tarsus 7.44–10.29 times longer than broad.

Abdomen. Tergal chaetotaxy 4: 5–6: 7–8: 7–10: 9–10: 9–10: 11–12: 10–11: 8: 6: 0: 0; sternal chaetotaxy 10: 36–40: 16–18: 15–16: 13–16: 13–14: 14:12: 8: 2: 2.

Dimensions (in mm). Body length 2.58–2.79. Pedipalp: trochanter 0.27–0.28/0.19–0.20, femur 0.88–1.04/0.17–0.19, patella 0.35–0.42/0.19–0.2, chela (with pedicel) 1.56–1.6/0.27–0.29, movable finger 0.75–0.89, hand 0.68–0.85/0.27–0.28. Chelicera: total 0.5–0.52/0.24–0.25, movable finger 0.25–0.3, hand 0.2–0.27/0.24–0.25. Carapace 0.6–0.68/0.59–0.61; anterior eye 0.07–0.08; posterior eye 0.07–0.08. Leg I: trochanter 0.2–0.22/0.15–0.18, femur 0.43–0.57/0.11, patella 0.34–0.38/0.09–0.1, tibia 0.29–0.33/0.07–0.08, tarsus 0.56–0.64/0.06–0.07. Leg IV: trochanter 0.3–0.35/0.17–0.22, femur+patella 0.86–0.93/0.25, tibia 0.62–0.68/0.12–0.13, metatarsus 0.28–0.35/0.09–0.1, tarsus 0.5–0.67/0.6–0.07.

Sequence data. GenBank Accession No. PX533168. It differs from other Korean species by 13.2% (A. buanensis) to 19% (A. maximus sp. nov.) pairwise divergences in the CO1 data respectively.

Allochthonius maximus Jeong and Harms sp. nov.

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LSID: urn:lsid:zoobank.org:act:3C5116C3-D9BB-4B2B-90F1-777F0DC48554

Type material. Holotype: Korea ♂; Gyeongsangbukdo-Province, Yeongcheon-si, Hwabuk-myeon, Janggak-ri, 1121; 36°07′45.29″N, 128°16′18.31″E; 22 May. 2023; JH Oh leg; NIBRIV0000932087 (NIBR). Paratypes 2♀; the same data as the holotype; NIBRIV0000932087 (NIBR; 1♀), JBNU-JH25B (JBNU, 1♀).

Etymology. The specific epithet maximus refers to its status as the largest epigean species within Allochthonius, reaching a body length of approximately three mm.

Diagnosis. This species closely resembles Allochthonius coreanus (Morikawa, 1970) in its relatively large body size (2.01–2.43 mm in A. coreanus, 2.59–3.03 mm in A. maximus sp. nov.) and the number of marginal teeth on the fixed chelal teeth (24–30 in A. coreanus, 25–26 in A. maximus sp. nov.), and the presence of six setae on the cheliceral palm. Both species differ in the number of marginal teeth on the movable finger (27–31 in A. coreanus vs 22–23 in A. maximus sp. nov.), the number of carapacal setae (10-4: 28 in A. coreanus vs 10-4: 26 in A. maximus sp. nov.), and the shape of female’s chelal finger (normal in A. coreanus vs strongly curved in A. maximus sp. nov.).

Description.

Holotype, male, adult (Figs. 10A–10B)

(A) Male adult, dorsal view; (B) male adult, ventral view; (C) female adult, dorsal view; (D) female adult, ventral view.

Colour. Male body dark brown; pedipalps strongly sclerotized.

Cephalothorax (Figs. 11A–11C, 12A). Carapace 0.93 times longer than broad; rectangular; four distinct eyes; epistome absent; carapace with 26 setae, five pairs on the anterior margin (A1, A2, A3, A4, A5), a pair of seate on the lateral margin (Ol), five pairs on the medial margin (Om1, Om2, Ml, Mm, Il), two setae pairs on the posterior margin (Pl, Pm). Two acuminate setae on the manducatory process, maxilla with three setae; coxal chaetotaxy 3: 4: 5: 7; coxal spines with ten short blades on a common mound; bisetose intercoxal tubercle present between coxa III and IV.

(A) Coxal spines; (B) left chelicera, dorsal view; (C) serrula exterior; (D) rallum; (E) right pedipalp, dorsal view; (F) right chela, lateral view.

Chelicera (Figs. 11D, 12B–12D). Palm smooth and with six setae, one seta on the movable finger; four marginal teeth on the fixed finger, large tooth basally positioned on the fixed finger; 11 marginal teeth on the movable finger; rallum with 10 blades; serrula exterior with 21 blades.

Pedipalp (Figs. 12B–12F, 13E–13F). Trochanter 1.42 times, femur 4.16 times, patella 1.85 times, chela 4.92 times, hand 2.01 times longer than broad, movable finger 2.91 times longer than the hand. Fixed finger with eight trichobothria, movable finger with four trichobothria; isb and ib basally positioned on the dorsum of the fixed finger; eb, ist, and esb grouped together, ist positioned closer to esb than eb; est and it located on the middle of the fixed finger, closer to tip; et positioned next to xs; xs terminally positioned on the fixed finger; sb, b, and t separately located from st; st basally positioned on the movable finger. Fixed finger with 25–24, movable finger 20 marginal teeth.

Legs. Leg I: trochanter 1.73 times, femur 3.75 times, patella 2.95 times, tibia 3.62 times, tarsus 9.38 times longer than broad. Leg IV: trochanter 1.69 times, femur+patella 2.75 times, tibia 4.46 times, metatarsus 3.11 times, tarsus 6.68 times longer than broad; arolium undivided.

Abdomen. Pleural membrane granulate; tergites undivided; tergal chaetotaxy 4: 6: 6: 9: 10: 10: 12: 10: 8: 6: 0: 0; sternites III–V divided; sternal chaetotaxy 8: 28: 16: 18: 16: 12: 10: 8: 6: 2: 2.

Dimensions (in mm). Body length 2.15. Pedipalp: trochanter 0.27/0.19, femur 0.79/0.19, patella 0.36/0.19, chela (with pedicel) 1.27/0.26, movable finger 0.75, hand 0.52/0.26. Chelicera: total 0.52/0.24, movable finger 0.28, hand 0.24/0.24. Carapace 0.52/0.56; anterior eye 0.06; posterior eye 0.05. Leg I: trochanter 0.23/0.13, femur 0.44/0.12, patella 0.32/0.11, tibia 0.29/0.08, tarsus 0.6/0.06. Leg IV: trochanter 0.28/0.17, femur+patella 0.73/0.27, tibia 0.55/0.12, metatarsus 0.26/0.09, tarsus 0.41/0.06.

Paratypes, female, adult (n = 2) (Figs. 10C–10D)

Colour. Female body pale brown; pedipalps strongly sclerotized.

Cephalothorax. Carapace 0.98 times longer than broad; with 26 setae; 10 setae on the anterior margin, and four setae on the posterior margin. Coxal chaetotaxy 3: 4–5: 4–5: 7–8; coxal spines with 10–11 blades.

Pedipalp. Trochanter 1.46–1.48 times, femur 5.45–6.2 times, patella 2.12–2.23 times, chela 4.37–6.12 times, hand 1.73–1.92 times longer than broad, movable finger 1.52–2.18 times longer than the hand. Fixed finger with 25–26, movable finger 22–23 marginal teeth. Both fingers strongly curved.

Legs. Leg I: trochanter 1.1 times, femur 6.28 times, patella 4.34 times, tibia 4.75 times, tarsus 10.26 times longer than broad. Leg IV: trochanter 1.66 times, femur+patella 4.3 times, tibia 6.01 times, metatarsus 4 times, tarsus 9.9 times longer than broad.

Abdomen. Tergites undivided; tergal chaetotaxy 4: 6: 6: 8–9: 9: 9–10: 12: 10: 8–9: 6: 0: 0; sternites III–IV divided, sternite V partly divided; sternal chaetotaxy 10–11: 28: 16–20: 16: 16: 14: 12: 12: 10: 2: 2.

Dimensions (in mm). Body length 2.59–3.03. Pedipalp: trochanter 0.31–0.33/0.21–0.23, femur 1.34–1.35/0.22–0.25, patella 0.50–0.54/0.24–0.25, chela (with pedicel) 1.72–2.02/0.33–0.39, movable finger 1.04–1.39, hand 0.63–0.68/0.33–0.39. Chelicera: total 0.60–0.61/0.26–0.29, movable finger 0.29–0.31, hand 0.3/0.29–0.31. Carapace 0.67–0.69/0.68–0.7; anterior eye 0.06–0.07; posterior eye 0.07. Leg I: trochanter 0.22–0.26/0.19–0.2, femur 0.64–0.7/0.11–0.13, patella 0.43–0.48/0.1–0.11, tibia 0.37–0.38/0.08–0.09, tarsus 0.73–0.74/0.07–0.08. Leg IV: trochanter 0.33–0.35/0.21, femur+patella 1.10–1.15/0.27–0.28, tibia 0.71–0.81/0.13–0.14, metatarsus 0.37/0.09, tarsus 0.7–0.75/0.07.

Sequence data. GenBank Accession No. PX921017. It differs from other Korean species by 16.2% (A. coreanus) to 24.3% (A. rufimanus sp. nov.) pairwise divergences in the CO1 data respectively.

Allochthonius opticus (Ellingsen, 1907)

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Remarks. The Korean record of this species by Lee & Seo (1995) is considered a misidentification and does not represent A. opticus s. str. The original type locality of A. opticus is Okayama in Japan (Ellingsen, 1907) but all recent taxonomic studies on Allochthonius have pointed to very small distribution ranges, short-range endemism, and poor dispersal capacities in this genus (Lin et al., 2025) and other pseudotyrannochthoniids (You et al., 2023; (Jeong et al., 2025; Harms et al., 2025). Considering the molecular taxonomic and ecological data now available for the genus, it is likely that the range of A. opticus is restricted to the Okayama Prefecture on Honshu Island, Japan. For details, see discussion (5. 1. Taxonomy of Allochthonius in South Korea).

Allochthonius rufimanus Jeong and Harms sp. nov.

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LSID: urn:lsid:zoobank.org:act:9C6953B6-1649-4129-A09F-D5501270B933

Type material. Holotype: KOREA ♂; Gyeongsangnamdo-Province, Sacheon-si, Sanam-myeon, Gacheon-ri, 333-1; 35°0′2.76″N, 128°7′33.17″E; 31 Mar 2024; KH Jeong and J Park leg; NIBRIV0000932088 (NIBR). Paratypes 9♀, 12♂; the same data as the holotype; NIBRIV0000932088 (NIBR; 1♀), ZMH-A@@ (ZMH; 3♀, 3♂), JBNU-KH100GN-A (JBNU, 5♀, 8♂).

Etymology. The specific epithet rufimanus is derived from the Latin rufus (reddish, red) and manus (hand), referring to the distinctly reddish pedipalpal hand (chela).

Diagnosis. This species most closely resembles Allochthonius liaoningensis Hu and Zhang, 2012 in the following characteristics: carapace with 24 setae, number of marginal teeth on the chelal finger (20 in A. liaoningensis, 17–20 in fixed finger, 15–18 in movable finger of A. rufimanus sp. nov.). Both species differ by the following characteristics: number of setae on the cheliceral palm (five in A. rufimanus sp. nov. vs six in A. liaoningensis), L/W ratio of leg I tarsus (7.77–8.94x in A. rufimanus sp. nov. vs 9.17–10x in A. liaoningensis), and L/W ratio of leg IV tarsus (7.26–8.51x in A. rufimanus sp. nov. vs 9.17–10.4x in A. liaoningensis).

Description.

Holotype, male, adult (Figs. 13A–13B)

Colour. Body light brown; pedipalps weakly sclerotized; tip of pedipalp red.

Cephalothorax (Figs. 14A–14C, 15A). Carapace 0.98 times longer than broad; rectangular; four distinct eyes; epistome absent; 24 setae on the carapace; five pairs of setae on the anterior margin (A1, A2, A3, A4, A5), a pair of setae on the lateral margin (Ol), four setae pairs on the medial margin (Om2, Ml, Mm2, Il), two pairs of setae on the posterior margin (Pl, Pm). Two acuminate setae on the manducatory process, maxilla with three setae; coxal chaetotaxy 3: 5: 6: 6; coxal spines with seven blades; bisetose intercoxal tubercle present between coxa III and IV.

Chelicera (Figs. 14D, 15B–15D). Palm smooth; five setae on the palm, one seta on the movable finger; six large marginal teeth on the fixed finger, 16 small marginal teeth on the movable finger; rallum with eight blades; serrula exterior with 15 blades.

Pedipalp (Figs. 14B–14F, 15E–15F). Trochanter 1.38 times, femur 4.91 times, patella 1.92 times, chela 4.71 times, hand 0.18 times longer than broad, movable finger 0.9 times longer than hand. Fixed finger with eight trichobothria, movable finger with four trichobothria; isb and ib basally positioned on the dorsum of the fixed finger; eb positioned on the lateral of the fixed finger; ist and esb grouped together, about one areolar apart; it and est positioned at the middle of the fixed finger; et positioned next to xs; xs terminally located on the fixed finger; sb, b, and t separately positioned from st; st basally positioned on the movable finger. Fixed finger with 21, movable finger with 17 marginal teeth.

Legs. Leg I: trochanter 1.63 times, femur 3.86 times, patella 3 times, tibia 3 times, tarsus 8 times longer than broad. Leg IV: trochanter 1.45 times, femur+patella 2.53 times, tibia 3.67 times, metatarsus 3 times, tarsus 10 times longer than broad; arolium undivided; pseudotactile setae present basally on leg IV metatarsus and tarsus.

Abdomen. Pleural membrane granulate; tergites undivided; tergal chaetotaxy 4: 4: 6: 6: 6: 8: 8: 10: 8: 6: 2: 0; sternite III–V divided; sternal chaetotaxy 8: 20: 20: 16: 14: 14: 14: 12: 6: 2: 2.

Dimensions (in mm). Body length 1.47. Pedipalp 0.18/0.13, femur 0.54/0.11, patella 0.23/0.12, chela (with pedicel) 0.80/0.17, movable finger 0.48, hand 0.3/0.17. Chelicera: total 0.36/0.18, movable finger 0.18, hand 0.2. Carapace 0.41/0.42; anterior eye 0.04, posterior eye 0.03. Leg I: trochanter 0.13/0.08, femur 0.27/0.07, patella 0.18/0.06, tibia 0.15/0.05, tarsus 0.32/0.04. Leg IV: trochanter 0.16/0.11, femur+patella 0.43/0.17, tibia 0.33/0.09, metatarsus 0.15/0.05, tarsus 0.3/0.03.

Paratype, male, adult (n = 12)

Cephalothorax. Carapace 0.92–1 time longer than broad; with 24 setae; 10 setae on the anterior margin, and four setae on the posterior margin. Coxal chaetotaxy 3–5: 5–7: 4–6: 6–7; coxa I with eight blades.

Pedipalp. Trochanter 1.4–1.41 times, femur 4.62–4.86 times, patella 1.79 times, chela 4.57–4.62 times, hand 1.74–1.78 times longer than broad, movable finger 1.56–1.66 times longer than the hand. Fixed finger with 18–19, movable finger with 16–19 marginal teeth.

Legs. Leg I: trochanter 1.31–1.47 times, femur 4.12–4.28 times, patella 2.67–3.12 times, tibia 3.04–3.27 times, tarsus 7.9–8.94 times longer than broad. Leg IV: trochanter 1.4 times, femur+patella 2.49–2.74 times, tibia 3.85–3.89 times, metatarsus 2.61–2.8 times, tarsus 7.58–7.78 times longer than broad.

Abdomen. Tergal chaetotaxy 4: 4: 6: 6: 6: 7–8: 8–10: 10: 6–7: 6: 0–2: 0; sternal chaetotaxy 8–9: 27–32: 16–20: 16–18: 14–15: 14: 12–15: 10–11: 6–7: 2–4: 2.

Dimensions (in mm). Body length 1.43–1.47. Pedipalp: trochanter 0.17–0.18/0.12–0.13, femur 0.53–0.54/0.11, patella 0.21–0.22/0.11–0.12, chela (with pedicel) 0.79–0.81/0.17–0.18, movable finger 0.49–0.5, hand 0.3–0.31/0.17–0.18. Chelicera: total 0.35–0.37/0.18–0.19, movable finger 0.19–0.2, hand 0.16–0.17/0.18–0.19. Carapace 0.38–0.40/0.40–0.42; anterior eye 0.04; posterior eye 0.04. Leg I: trochanter 0.12–0.14/0.08–0.1, femur 0.24–0.28/0.06–0.07, patella 0.16–0.19/0.06, tibia 0.14–0.16/0.05, tarsus 0.31–0.32/0.04. Leg IV: trochanter 0.17/0.12, femur+patella 0.41–0.46/0.16–0.17, tibia 0.31–0.34/0.08–0.09, metatarsus 0.14–0.15/0.05–0.06, tarsus 0.3/0.04.

Paratypes, female, adult (n = 9) (Figs. 13C–13D)

Cephalothorax. Carapace 0.79–0.91 times longer than broad; with 24 setae; 10 setae on the anterior margin, and four setae on the posterior margin. Coxal chaetotaxy 3–4: 5–6: 5–6: 5–7; coxal spines with eight blades.

Pedipalp. Trochanter 1.33–1.37 times, femur 4.28–4.48 times, patella 1.7–1.93 times, chela 3.93–4.01 times, hand 1.42–1.61 times longer than broad, movable finger 1.44–1.83 times longer than hand. Fixed finger with 17–20, movable finger with 15–18 marginal teeth.

Legs. Leg I: trochanter 1.13–1.18 times, femur 4.49–4.85 times, patella 2.95–3.39 times, tibia 3.54–3.81 times, tarsus 7.77–8.92 times longer than broad. Leg IV: trochanter 1.37–1.39 times, femur+patella 3.28–3.4 times, tibia 3.79–4.04 times, metatarsus 2.66–2.88 times, tarsus 7.26–8.51 times longer than broad.

Abdomen. Tergites undivided; tergal chaetotaxy 4: 4: 6: 6–7: 7: 8–9: 9: 9–10: 8: 6: 0: 0; sternites III–IV divided; sternal chaetotaxy 8–10: 20–22: 12–20: 14–16: 14: 12–15: 12–16: 12: 6: 2: 2.

Dimensions (in mm). Body length 1.59–1.67. Pedipalp: trochanter 0.19–0.21/0.14–0.16, femur 0.56–0.62/0.13–0.14, patella 0.24–0.25/0.12–0.15, chela (with pedicel) 0.94–0.96/0.24, movable finger 0.56–0.62, hand 0.34–0.38/0.24. Chelicera: total 0.43–0.44/0.22, movable finger 0.23–0.24, hand 0.2/0.22. Carapace 0.38–0.44/0.48; anterior eye 0.04–0.05; posterior eye 0.04–0.05. Leg I: trochanter 0.12–0.13/0.1–0.11, femur 0.32–0.35/0.07, patella 0.18–0.21/0.06, tibia 0.18/0.05, tarsus 0.33–0.34/0.04. Leg IV: trochanter 0.19/0.14, femur+patella 0.50–0.51/0.15–0.16, tibia 0.32–0.36/0.09, metatarsus 0.16/0.06, tarsus 0.28–0.33/0.04.

Sequence data. GenBank Accession No. PX533173. This species differs from other Korean species by 17% (A. jungsuni sp. nov.) to 24.3% (A. maximus sp. nov.) pairwise divergence in the CO1 data respectively.

Interspecific pairwise genetic distances

Recent studies indicate that about 7% of genetic differences in the CO1 gene could delineate pseudotyrannochthoniids (Jeong et al., 2025; Harms et al., 2025). We also adapted this value since those studies were also focused on the same family, Pseudotyrannochthoniidae. Our interspecific pairwise genetic distance supports the species hypothesis derived from morphology and implies the presence of at least five species of Allochthonius in the Republic of Korea (Table 1). Genetic distances range between 13.2% to 24.3%. The pairwise genetic distance between A. buanensis and A. jungsuni sp. nov. is 13.2% and the genetic distance between A. rufimanus sp. nov. and A. maximus sp. nov. is 24.3%.

Discussion

Taxonomy of Allochthonius in South Korea

Pseudoscorpiones has been understudied in Korea, and the taxonomy is still in a state of flux, despite some recent advances (You et al., 2022; Jeong et al., 2025). Although Allochthonius is the most commonly collected pseudoscorpion genus in Korea and also the most diverse genus in the family Pseudotyrannochthoniidae, only three species have been reported from the Korean Peninsula to date. The first study was conducted by Morikawa (1970), who discovered A. coreanus and treated it as a subspecies of A. opticus. Lee (1982) subsequently described A. buanensis, but the diagnosis relied on a few characters such as the number of carapacal setae. Bang (1984) later elevated A. coreanus to full species rank, and Lee & Seo (1995) reported A. opticus, a species originally described from Japan, from Korea. However, as noted above, all Korean records were based on limited examinations and the original type materials are no longer available Therefore, we conducted an integrative taxonomic revision based on newly collected specimens from type localities.

The occurrence of Allochthonius opticus in Korea has long been uncertain. Originally described from Japan by Ellingsen (1907) and later subdivided into several subspecies by Morikawa (1960), A. opticus was reported from Korea only by Lee & Seo (1995). Their specimens were not assigned to either of the Japanese subspecies recognized by Morikawa (1956) –Allochthonius opticus opticus (Elligsen, 1907) and A. opticus troglophilus (Morikawa, 1956), the latter collected from Taniai-mura, Gifu Prefecture –lacked detailed comparison and are no longer available for study. Comparison of their descriptions with A. opticus s. str. reveals differences in setal counts and appendage size (Table 2), suggesting that the Korean material is unlikely to be conspecific. Given the absence of verifiable Korean material, the taxonomic identity of the reported specimens cannot be confirmed. Allochthonius opticus is therefore excluded from the Korean fauna in the present revision.

Table 2. Morphological comparison between Korean Allochthonius opticus and two morphological forms of A. opticus s. str.

	Korean A. opticus	Young adult form of A. opticus s. str.	Old adult form of A. opticus s. str.
Number of carapacal setae	10-4: 28	10-4: 26	10-4: 28
Number of setae on tergite I	Four	Six	Four
Length of chela	<1.3 mm	<1.3 mm	>1.4 mm
Length of pedipalpal femur	<0.9 mm	<0.9 mm	>0.9 mm

Open in a new tab

Taxonomic status of Japanese Allochthonius subspecies

Almost all molecular studies indicate that basal lineages of pseudoscorpions, such as members of the suborder Heterosphyronida, exhibit narrow-range endemism, which can promote speciation and diversification, specifically in isolated terrains such as mountain ranges, forest fragments, and karst systems (Edward & Harvey, 2008; Harms, Roberts & Harvey, 2019; Hlebec et al., 2023; Harms et al., 2025). Recent advances in pseudoscorpion taxonomy further suggest that subtle morphological differences are indicative of species status and replace rather broad historical concepts of morphologically variable species (Hlebec et al., 2023; Hlebec et al., 2024; Muster et al., 2024). Following a recent example (You et al., 2022) in which all subspecies of the Asian genus Spelaeochthonius were elevated to full species rank, we likewise update historical species concepts for Allochthonius and elevate the subspecies described by Morikawa (1954); Morikawa (1956); Morikawa (1960) to full species level.

Although Morikawa’s type specimens are currently inaccessible, the original taxonomic descriptions are fairly complete, and the subspecies can be distinguished by discrete diagnostic morphological characters that clearly justify species-level recognition today (Morikawa, 1960). Originally, Allochthonius ishikawai (Morikawa, 1954) comprised six subspecies: A. i. deciclavatus Morikawa, 1956; A. i. ishikawai Morikawa, 1954; A. i. kyushuensis Morikawa, 1960; A. i. shiragatakiensis Morikawa, 1954; A. i. uenoi Morikawa, 1956; and A. i. uyamadensis (Morikawa, 1954). We elevate all these subspecies to species-level: Allochthonius deciclavatus stat. nov., Allochthonius kyushuensis stat. nov., Allochthonius shiragatakiensis stat. nov., Allochthonius uenoi stat. nov., and Allochthonius uyamadensis stat. nov. Additionally, two subspecies have been recognized under Allochthonius opticus Ellingsen, 1907: A. o. opticus Ellingsen, 1907 and A. o. troglophilus Morikawa, 1956. We elevate A. o. troglophilus to species level as Allochthonius troglophilus stat. nov. An identification key for the taxa formerly regarded as subspecies of A. ishikawai and A. opticus is presented in the ‘Identification Key’. With this step, we have simplified the taxonomy of Pseudotyrannochthoniidae in Asia and are able to provide biologically and taxonomically more meaningful species concepts. In summary, Allochthonius now includes 43 species in Japan (15 species), China (14 species), Taiwan (seven species), Russia (one species), and Korea (five species). It is the most diverse genus of the Pseudotyrannochthoniidae with potentially many more species to be discovered in the future.

Cryptic diversity of Allochthonius in Korea

The present study provides a taxonomic baseline for more work on Allochthonius in Korea and adds three new species to the country record (Morikawa, 1970; Lee, 1982; Lee & Seo, 1995); this study). This is still a low number compared to those in neighboring countries, and we suggest that more species will be described from the Korean Peninsula in the future. Allochthonius is a genus that can be found in both epigean and subterranean habitats (Morikawa, 1960; Viana & Ferreira, 2021; Gao, Hou & Zhang, 2023). In neighboring countries, such as China and Japan, several subterranean species are included (Morikawa, 1954; Morikawa, 1956; Viana & Ferreira, 2021)(Gao Hou & Zhang, 2024; Li, 2023). However, on the Korean Peninsula, no subterranean Allochthonius has yet been discovered. Considering that the Korean Peninsula possesses more than a thousand caves, including both limestone karsts and lava tubes (Woo et al., 2015; Woo & Kim, 2018), it is likely that Allochthonius could be distributed underground in Korea. Moreover, even among epigean species, a barcoding study suggested cryptic species within Allochthonius buanensis a species complex (Ohira et al., 2018). In summary, considering the landscape of the Korean Peninsula and related studies, it is likely that a high diversity of Allochthonius is inherent to this region. Therefore, extensive field surveys and molecular work are necessary to unveil the diversity of this fauna.

Identification key

Identification key differentiating former subspecies of Allochthonius ishikawai:

1. Pedipalpal femur 5.1–5.4 times longer than broad …A. deciclavatus stat. nov. (Matsubarano-ana cave, Yamaguchi Prefecture, Japan)

- Pedipalpal femur 5.8–7.5 times longer than broad …2

2. Five pairs of setae on the anterior margin of carapace (A0–A5) …A. kyushuensis stat. nov. (Goya daiichi-do cave, Fukuoka Prefecture, Japan)

- Four pairs of setae on the anterior margin of carapace (A0–A4) …3

3. 18 setae on the carapace …A. uyamadensis stat. nov. (Uyama-do cave, Okayama Prefecture, Japan)

- More than 19 setae on the carapace …4

4. 24 setae on the carapace; carapace more than 0.6 mm …A. uenoi stat. nov. (Komakado-kaza-ana cave, Shizuoka Prefecture, Japan)

- 20 setae on the carapace; carapace less than 0.6 mm …5

5. 13–16 marginal teeth on both chelal finger; fingers not curved …A. ishikawai (Ryuga-do cave, Kochi Prefecture, Japan)

- 9–11 marginal teeth on both chelal finger; fingers strongly curved …A. shiragatakiensis stat. nov. (Shiragataki-do cave, Ehime Prefecture, Japan)

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Identification key differentiating former subspecies of Allochthonius opticus

1. Pedipalpal femur 4.4–5.5 times longer than broad …A. opticus (Okayama, Okayama Prefecture, Japan)

- Pedipalpal femur 5.5–6.1 times longer than broad …A. troglophilus stat. nov. (Kugo cave, Gifu Prefecture, Japan)

Open in a new tab

Conclusions

The genus Allochthonius is widely distributed in East Asia; however, its diversity in the Republic of Korea has remained poorly studied since the 1990s. In this study, we revise Korean Allochthonius using an integrative taxonomic framework and describe three new species, A. jungsuni sp. nov., A. maximus sp. nov., and A. rufimanus sp. nov., each supported by diagnostic morphological characters. Interspecific pairwise genetic distances further corroborate the presence of at least five distinct Allochthonius species in Korea.

Our comparative morphological analyses and review of previous taxonomic literature support the elevation of several subspecies to species rank, including A. deciclavatus stat. nov., A. kyushuensis stat. nov., A. shiragatakiensis stat. nov., A. uenoi stat. nov., A. uyamadensis stat. nov., and A. troglophilus stat. nov. Conversely, A. opticus is excluded from the Korean fauna based on clear morphological discrepancies with A. opticus sensu stricto.

Although relatively few species of Allochthonius are currently recognized from Korea, the peninsula’s complex geography and molecular evidence suggest the presence of additional, potentially cryptic diversity. Continued integrative taxonomic studies incorporating extensive sampling, detailed morphology, and molecular data will be essential for a comprehensive understanding of Korean pseudoscorpion diversity.

Supplemental Information

Supplemental Information 1. Sequences dataset.

peerj-14-21332-s001.fas^{(3.1KB, fas)}

DOI: 10.7717/peerj.21332/supp-1

Acknowledgments

We thank Jonghwa Oh (Seoul National University, Republic of Korea) and Jinsung Park (Jeonbuk National University, Republic of Korea) and Youngbin Cha (Korea National Arboretum, Republic of Korea) for their assistance with field sampling. We are also grateful to Nadine Dupérré (Leibniz Institute for the Analysis of Biodiversity Change, Germany) and Kwang-Soo Kim (National Institute of Biological Resources, Republic of Korea) for their help with specimen deposition in institutional collections.

Funding Statement

This work was supported by a grant from the National Institute of Biological Resources (NIBR), funded by the Ministry of Environment (MOE) of the Republic of Korea (NIBR202502102). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Additional Information and Declarations

Competing Interests

The authors declare there are no competing interests.

Author Contributions

Kyung-Hoon Jeong conceived and designed the experiments, performed the experiments, analyzed the data, prepared figures and/or tables, authored or reviewed drafts of the article, funding acquisition, and approved the final draft.

Danilo Harms conceived and designed the experiments, analyzed the data, authored or reviewed drafts of the article, and approved the final draft.

Sora Kim conceived and designed the experiments, authored or reviewed drafts of the article, funding acquisition, and approved the final draft.

Data Availability

The following information was supplied regarding data availability:

The sequences used in this study are available at GenBank: PX533168, PX921017, and PX533173.

New Species Registration

The following information was supplied regarding the registration of a newly described species:

Publication LSID: urn:lsid:zoobank.org:pub:A53E1EB1-DE99-45D8-B92B-E538649EEB13

Allochthonius jungsuni: urn:lsid:zoobank.org:act:EA291957-FD99-4772-8DD1-C7E566C242D8

Allochthonius maximus: urn:lsid:zoobank.org:act:3C5116C3-D9BB-4B2B-90F1-777F0DC48554

Allochthonius rufimanus: urn:lsid:zoobank.org:act:9C6953B6-1649-4129-A09F-D5501270B933.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplemental Information 1. Sequences dataset.

peerj-14-21332-s001.fas^{(3.1KB, fas)}

DOI: 10.7717/peerj.21332/supp-1

Data Availability Statement

The following information was supplied regarding data availability:

The sequences used in this study are available at GenBank: PX533168, PX921017, and PX533173.

[ref-1] Bang (1984).Bang SK. M. Sc. in Bology. 1984. A study of systematics of order Pseudoscorpiones in Korea. [Google Scholar]

[ref-2] Benavides et al. (2019).Benavides LR, Cosgrove JG, Harvey MS, Giribet G. Phylogenomic interrogation resolves the backbone of the Pseudoscorpiones tree of life. Molecular Phylogenetics and Evolution. 2019;139:106509. doi: 10.1016/j.ympev.2019.05.023. [DOI] [PubMed] [Google Scholar]

[ref-3] Chamberlin (1929).Chamberlin JC. On some false scorpions of the suborder Heterosphyronida (Arachnida–Chelonethida) Canadian Entomologist. 1929;61:152–155. doi: 10.4039/Ent61152-7. [DOI] [Google Scholar]

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PERMALINK

Korean dragon pseudoscorpions revisited: a taxonomic review of Allochthonius (Pseudoscorpiones: Pseudotyrannochthoniidae) Chamberlin, 1929 with three new species

Kyung-Hoon Jeong

Danilo Harms

Sora Kim

Abstract

Introduction

Materials and methods

Morphological identification

Molecular analyses

Table 1. Interspecific genetic divergences within all Korean Allochthonius species.

Nomenclatural acts

Result

Taxonomy

Figure 1. Habitus of Allochthonius buanensisLee, 1982.

Figure 2. Drawings of Allochthonius buanensisLee, 1982.

Figure 3. Scanning electron images of Allochthonius buanensisLee, 1982.

Figure 4. Habitus of Allochthonius coreanusMorikawa, 1970.

Figure 5. Drawings of Allochthonius coreanusMorikawa, 1970.

Figure 6. Scanning electron images of Allochthonius coreanusMorikawa, 1970.

Figure 7. Habitus of Allochthonius jungsuni sp. nov.

Figure 8. Drawings of Allochthonius jungsuni sp. nov.

Figure 9. Scanning electron images of Allochthonius jungsuni sp. nov.

Figure 10. Habitus of Allochthonius maximus sp. nov.

Figure 11. Drawings of Allochthonius maximus sp. nov.

Figure 12. Scanning electron images of Allochthonius maximus sp. nov.

Figure 13. Habitus of Allochthonius rufimanus sp. nov.

Figure 14. Drawings of Allochthonius rufimanus sp. nov.

Figure 15. Scanning electron images of Allochthonius rufimanus sp. nov.

Interspecific pairwise genetic distances

Discussion

Taxonomy of Allochthonius in South Korea

Table 2. Morphological comparison between Korean Allochthonius opticus and two morphological forms of A. opticus s. str.

Taxonomic status of Japanese Allochthonius subspecies

Cryptic diversity of Allochthonius in Korea

Identification key

Conclusions

Supplemental Information

Acknowledgments

Funding Statement

Additional Information and Declarations

Competing Interests

Author Contributions

Data Availability

New Species Registration

References

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

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