Chthonius (Chthonius) heterodactylus Tomosvary 1882

Chthonius (C.) heterodactylus Tömösváry, 1882

(Figs 12–33, 90)

Chthonius Rayi (not L. Koch, 1873): Tömösváry 1882: 240, figs 13–4 plate 5 (misidentification).

Chthonius heterodactylus Tömösváry 1882: 241, figs 1–2 plate 5.

Chthonius tetrachelatus (not Preyssler, 1790): Daday 1889a: 134; Daday 1889b: 190 (misidentification, in part: Sinnaikő).

Chthonius diophthalmus Daday 1889a: 134, figs 21, 27 plate 4 (n. syn.).

Chthonius cavernarum Ellingsen 1909: 214 (in part).

Chthonius (Chthonius) orthodactylus gracilis Beier 1935: 31, fig. 1 (n. syn.).

Chthonius (Chthonius) ksenemani Hadži 1939: 184, figs 1a–e, 2, 3a–d (n. syn.).

Chthonius (Chthonius) diophthalmus (not Daday, 1889a): Beier 1939a: 2, fig. 1 (misidentification, in part: see C. hungaricus); Mahnert 1978: 287, figs 35a–b; Krumpál & Kiefer 1981: 127, figs 1–5; Schawaller 1989: 6, figs 15–16; Christophoryová et al. 2011b: 39, figs 1C–1D, 2B; Novák 2012: 60, figs 2A, 2H.

Chthonius (Chthonius) heterodactylus: Beier 1939a: 4, fig. 2; Kárpáthegyi 2006: 116, fig. 2; Ducháč et al. 2007: 31, figs 2–6; Christophoryová et al. 2011b: 40, figs 2C–2E; Novák 2012: 60.

Chthonius (Chthonius) leruthi Beier 1939a: 5, fig. 3 (n. syn.).

Type localities: Slovakia, Prešovský kraj, Bardejov (49°17′ N 21°16′ E) and Sninský kameň (48°55′40″ N 22°11′ 22″E); Romania, Judeţul Sǎlaj, Zalǎu (47°12′ N 23°03′ E).

Distribution. Czech Republic, Hungary, Germany, Poland, Romania, Slovakia, Ukraine.

Diagnosis (♂♀). An eyed, epigean Chthonius (Chthonius) from Western Sudetes to Southern Carpathians that differs from other species of the heterodactylus group in the following combination of characters: carapace usually with epistome, standard chaetotaxy mm 4mm:6:4:2:m 2m (24); chaetotaxy tergites I–IV: 4:4:4:4; genital opening of males flanked by scattered setae on each side; fixed chelal finger with 24–30 (♂) or 18–32 (♀) teeth with dental canals, usually without intercalary microdenticles, and a simple, not enlarged, distal paraxial seta; movable chelal finger with 18–30 low, reclined, visible teeth increasingly reduced towards the finger base, reaching back almost to sb; coupled sensilla pc of movable chelal finger usually between trichobothria st and sb; chela length 0.73–1.02 (♂) or 0.76–1.27 (♀), movable finger length 0.48–0.66 (♂) or 0.50–0.76 (♀).

Type material of Chthonius diophthalmus examined. ROMANIA— Caraş–Severin: 2 ♂ (syntypes),“613/ 1883. Mehádia, 1881. / Chthonius diophthalmus Daday / Det. Dr. Daday Jenö” “Pseudoscorp. 00240” (HNHM).

Type material of Chthonius leruthi examined. ROMANIA— Cluj: 1 ♀ (holotype) [left pedipalp missing], “ Chthonius leruthi n. sp. / type! ♀ Beier.” “Roumanie: Turda—Jara / 7.VI.1938 R. Leruth / 553 / Steinen im Buschwerk / 600 m / M. Beier det., 1939: / C. (Chthonius) Leruthi n. sp / type—1 ♀ / cf. Bull. Mus. Hist. Nat. Belg. / XV, 1939, n° 39, p. 5–7, fig. 3” “Index 35, Arachn. Mod. II. / Nom: Chthonius (Chthonius) / leruthi Beier (type) ♀ / Loc.: Roumanie: Sàcel—alt. 600 m N° 553 / (pierres enfoncées) / Date: 7.VI.1938 / Rec.: R. Leruth / Dét.: M. Beier 1939 ” (IRSNB); 2 ♀ (paratypes) [one lacking right chela, other lacking both pedipalps and chelicerae], “ Roumanie: Turda—Jara / 7.VI.1938 —R. Leruth (553 bis) / Humus, Laub, Buschwerk / 600 m / M. Beier det. 1939 / C. (Chthonius) Leruthi n. sp / 2 ♀ / Paratypes / cf. Bull. Mus. Hist. Nat. Belg. / XV, 1939, n° 39, p. 5–7, fig. 3” “Index 35, Arachn. Mod. II. / Nom: Chthonius (Chthonius) / leruthi Beier (Paratypes) 2 ♀ / Loc.: Roumanie: Sàcel—alt. 600 m N° 553bis / (feuilles mortes, humus) / Date: 7.VI.1938 / Rec.: R. Leruth / Dét.: M. Beier 1939 ” (IRSNB).

Other material examined. CZECH REPUBLIC— Olomouc: 1 ♂, Hranice, NPR Hůrka u Hranic, subteránni pasti, 10.IX/ 24.X.2005, J. Mikula & I. H. Tuf leg. (CUZP); 1 ♂ (without chelae), id., 19.VIII/ 3.X.2006, J. Mikula & I. H. Tuf leg. (CUZP); 2 ♀, id., 3.X/ 21.XI.2006, J. Mikula & I. H. Tuf leg. (CUZP).

HUNGARY— Észak Magyaroszág: 2 ♀ (C. heterodactylus, J. Novák det.), Bükk Mountains, Miskolc, Forrásvölgy, 9.IV.1964, I. Loksa leg., kaszálórét (HNHM); 1 ♀ (C. heterodactylus, J. Novák det.), Bükk Mountains, Nagyvisnyó, Lyány V., 1.XI.1989, Z. Korsós leg. (HNHM); 1 ♀ (C. diophthalmus, J. Novák det.), Bükk Mountains, Nagyvisnyó, Lyány V., 1.XI.1989, Z. Korsós leg. (HNHM).

POLAND— 2 ♂, 2 ♀ (C. heterodactylus, M. Beier det.) “Ost-Karpathen, Polen ” (NHMW); 2 ♂, 4 ♀ (C. heterodactylus, J. Rafalski det.) “ Polen, Piening [?] 950 m a.s.l. [under leaf litter and stones], IX.1932, Rafalski leg. (NHMW).

ROMANIA— Alba: 1 ♂, “ Roumanie: Alba –Sebes / 2.VII.1938 —R. Leruth (566) Steinen im Fichtenwald / 1000 m. M. Beier det., 1939 / C. (Chthonius) diophthalmus Daday ” “ Roumanie: Sugag. alt. 950 m. N° 566 / (pierres enfoncées) / 2.VII.1938 / R. Leruth” (IRSNB); 1 ♀, “ Roumanie: Alba –Abrud / 25.VII.1938 —R. Leruth. (581) Steinen im Fichtenwald / 650 m. M. Beier det., 1939 / C. (Chthonius) diophthalmus Daday / 1 ♀, 1 juv. ” “ Roumanie: Sohodol. alt. 650 m. / (pierres enfoncées) N° 581 / 25.VII.1938 / R. Leruth” (IRSNB); 3 ♀, 1T, Alba Iulia, Intregalde, 26.VIII.1987, G. Gardini & R. Rizzerio leg. Bihor: 1 ♀, “ Roumanie: Bihor–Beius / 5.VIII.1938 —R. Leruth (583) Steinen im Fichtenwald / 1150 m. M. Beier det., 1939 / C. (Chthonius) heterodactylus / 1 ♀ Tömösváry” “ Roumanie: Budureasa. alt. 1150 m / N° 583 (pierres enfoncées) / 5.VIII.1938 / R. Leruth” (IRSNB); 2 ♀, “ Roumanie: Bihor / 24.VIII.1938 —R. Leruth (R.99) Pesterea de la Searducel / 350 m. M. Beier det., 1939 / C. (Chtonius) [sic!] diophthalmus Daday / 1 ♂, 2♀” “ Roumanie: Vârciorog. alt. 350 m. R99 / (sur du bois) / 24.VIII.1938 / R. Leruth” (together with 1 ♂, 1 ♀ of C. hungaricus) (IRSNB). Cluj: 2 ♂, “ Roumanie: Câmpeni / Turda, 17.VII.1938 —R. Leruth 61A.—Pesterea de la / Pojarul çhetarului— 1000 m M. Beier det., 1939: / C. (Chthonius) diophthalmus Daday / 2 juv. ” “ Romanie: Scárisoara—alt. 1000 m. / (tamisage de mousses) / R.61A / 17.VII.1938 / R. Leruth” (IRSNB); 2 T, “ Roumanie: Turda–Jara / 18.VI.1938 —R. Leruth (559) Steinen im Fichtenwald / 1400 m M. Beier det. 1939 / C. (Chthonius) diophthalmus Daday 2 juv. ” “ Roumanie: Muntele—Báisoará / alt. 1400 m. N° 559 / (pierres enfoncées) / 18.VI.1938 / R. Leruth” (IRSNB); 1 ♂, “ Roumanie: Turda—Câmpeni / 22.VII.1938 —R. Leruth (579) Steinen in einer Doline / 900 m. M. Beier det., 1939: / C. (Chthonius) diophthalmus Daday. / 1 ♂ ” “ Roumanie: Scàrisoara. alt. 900 m. N° 579 / 22.VII.1938 / R. Leruth” (IRSNB); 3 ♂, “ Roumanie: Turda—Câmpeni / 24.VII.1938 —R. Leruth (580) Steinen im Fichtenwald / 800 m. M. Beier det., 1939: / C. (Chthonius) heterodactylus Tömösváry / 3 ♂ ” “ Roumanie: Albac. alt. 800 m. / N° 580 (pierres enfoncées) / 24.VII.1938 / R. Leruth” (IRSNB); 1 ♂, 2 ♀, “ Roumanie: Cluj / 3.VI.1938: R. Leruth (551) Steinen im Buchenwald / 500 m M. Beier det., 1939: / C. (Chthonius) diophthalmus Daday / 3 ♂ ” “Cluj—alt. 500 m. N° 551 / (pierres enfoncées) / 3.VI.1938 / R. Leruth” (IRSNB); 1 ♂, “ Roumanie: Turda—Jara / 7.VI.1938 —R. Leruth (553) Steinen im Buschwerk / 600 m. M. Beier det., 1939: C. (Chthonius) diophthalmus Daday / 1 ♂, 1,♀” “ Roumanie: Sàcel—alt. 600 m. N° 553 / (pierres enfoncées) / 7.VI.1938 / R. Leruth” (IRSNB); 1,♂, 1 ♀, “ Roumanie: Turda—Jara / 7.VI.1938 —R. Leruth (553bis) Laub im Bushwerk 600 m / M. Beier det., 1939 / C. (Chthonius) heterodactylus Tömösváry / 1 ♂, 1 ♀” “ Roumanie: Sàchel—alt. 600 m. N° 553bis / (feuilles mortes, humus) / 7.VI.1938 / R. Leruth” (IRSNB); 4 ♂, 2 D, “ Roumanie: Turda—Jara / 7.VI.1938 —R. Leruth (552) Steinen im Buchenwald / 650 m M. Beier det., 1939: / C. (Chthonius) diophthalmus Daday / 3 ♂, 1 ♀” “ Roumanie: Sàcel, alt. 650 m. N° 552 / (pierres enfoncées) / 7.VI.1938 / R. Leruth” (together with 1 ♀ of C. hungaricus) (IRSNB); 1 ♂, 1 ♀, Girda de Sus, entrance of the cave Coiba Mare, 1100 m a.s.l., 19.VIII.1987, G. Gardini & R. Rizzerio leg.; 5 ♂, 8 ♀, 2 T, Girda de Sus, Casa de Piatra, 20.VIII.1987, G. Gardini, R. Rizzerio & S. Zoia leg.; 1 ♂, Valea Albacului, Mătişeşti, loc. Peretele Dîrninii, 22.VIII.1987, G. Gardini & R. Rizzerio leg. Prahova: 1 ♀, “Carpathes / Sinaia Valachie / A. L. Montandon” “III. Chthonius cavernarum Ell. ” (E. Ellingsen det.) (paralectotype of C. cavernarum, see Remarks in C. cavernarum) (MSNG); 1 ♀, “Carpathes / Sinaia Valachie.” “139. Chthonius cavernarum Ell. ” (E. Ellingsen det.) (paralectotype of C. cavernarum, see Remarks under C. cavernarum) (MSNG).

SLOVAKIA— Prešovský kraj: 1 ♂, 3 ♀, 2 T, Vihorlat Mountains, close to Vihorlat hill, 6.VIII.1995, 48°55′N 22°10′E, F. Šťáhlavský leg., Fagus sylvatica leaf litter (NHMW, no. 27.583); 3 ♂, 5 D, id., close to Morske oko, 6.VIII.1995, 48°55′N 22°12′E, F. Šťáhlavský leg., Fagus sylvatica leaf litter (NHMW, no. 27.584); 1 ♂, Bukovske vrchy Mountains, Kremenec, 8.VIII.1995, 49°05′16″N 22°33′56″E, F. Šťáhlavský leg., Fagus sylvatica leaf litter (NHMW, no. 27.585); 1 ♂, 2T, id., 5.VII.2000, 49°05′16″N 22°33′56″E, F. Šťáhlavský leg., Fagus sylvatica leaf litter (NHMW, no. 27.586); 2 ♂, 5 ♀, 1 T, id., 25.VIII.2001, 49°05′16″N 22°33′56″E, F. Šťáhlavský leg., Fagus sylvatica leaf litter (NHMW, no. 27.587); 3 ♂, 7 ♀, Bukovske vrchy Mountains, Čierťaž, 26.VIII.2001, 49°05′29″N 22°30′49″E, F. Šťáhlavský leg., Fagus sylvatica leaf litter (NHMW, no. 27.588); 2 ♂, 2 ♀, Bukovske vrchy Mountains, Jarabá Skala, 26.VIII.2001, 49°05′55″N 22°25′23″E, F. Šťáhlavský leg., Fagus sylvatica leaf litter (NHMW, no. 27.589).

Description of adults (♂♀). Carapace, tergites, chelicerae and pedipalps pale brown; hispid granulation on lateral surfaces of carapace, on cheliceral palm and on base of cheliceral movable finger and, in males, on dorsal surface of pedipalpal hand and on base of chelal movable finger. Carapace 0.9–1.0 times longer than broad, subquadrate, slightly constricted posteriorly; anterior margin (Figs 12–13, 20) usually with small epistome in both sexes, rarely with close-set denticles slightly prominent; ocular area as in Figs 14, 21, anterior eyes with convex lens (diameter 0.040–0.055 mm), posterior ones with weak lens, all eyes with tapetum; distance from anterior eyes to anterior margin of carapace 0.030–0.050 mm; chaetotaxy mm 4mm:6:4:2:m 2m (24), macrosetae usually fine, rarely anterior row m 4m or m 4mm and posterior row m 2mm or mm 2mm, posterior lateral microsetae very short; length of anteromedian and anterolateral macrosetae respectively 0.10–0.15 and 0.06–0.11 mm, length of median macrosetae of the ocular row 0.11–0.18 mm, length of posterior macrosetae 0.10–0.14 mm. Chaetotaxy of tergites I–X 4:4:4:4:6:6:6:6:6:4. Chaetotaxy of sternites II–X 10:(3)8–10(3):(2)7–9(2):8–9:6:6:6:6:7; genital opening of males flanked by 10–13 (rarely 9 or 14) scattered setae on each side (Fig. 17). Chelicera (Figs 15–16, 22) 2.1–2.3 (♂) or 2.0–2.2 (♀) times as long as broad, palm with 6 setae and 2 (rarely 3) microsetae laterally; fixed finger with 9–14 teeth and 3–4 proximal microtubercles, the first two distal teeth larger; movable finger with a large isolated subapical tooth (di) and 7–10 teeth proximally reduced in size; gl ratio 0.51–0.60; spinneret usually prominent, rarely weakly prominent or absent, in males (Figs 32–33), prominent and apically rounded in females; rallum with 11 blades; serrulae interior and exterior respectively with 12 and 15–17 blades. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 4 + 3 marginal microsetae, II 4, III 5, IV 6; coxa II with 4–14 (usually 7–8) coxal spines, coxa III with 2–7 (usually 3–5) coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 4.9–6.2 (♂) or 4.75–6.0 (♀) times as long as broad; chela (Figs 18–19, 23–31) 5.0–5.8 (♂) or 4.3–5.2 (♀) times as long as deep; hand of chela 1.65–1.9 (♂) or 1.5–1.9 (♀) times as long as deep, faintly depressed proximad of ib/isb; fixed finger of males usually with slight sigmoid curvature in lateral view, this being more marked in females; fixed finger with 24–30 (usually 26–28) (♂) or 18–32 (usually 18–21) (♀) teeth with dental canals, usually without intercalary microdenticles; first distal tooth reduced, at level of trichobothria dx, rarely distad of dx; 20–27 (♂) or 15–19 (rarely 26) (♀) sharp, reclined teeth increasing in size as far as halfway along the finger, then reduced in size towards the finger base, followed by 3–7 low proximal teeth with rounded tips; base of fixed finger with 2–5 microtubercles; fixed finger at level of it/est with 4 (rarely 3 or 5) teeth occupying 0.1 mm (distance between successive apices 0.026–0.033 mm, rarely 0.023 or 0.037) in males, with 3 (rarely 4) teeth occupying 0.1 mm (distance between successive apices 0.036–0.050 mm, rarely 0.026) in females; tip of fixed finger with apical sensilla af1 ‾ 2, distal paraxial seta gradually sharp, curved and thin; movable finger with 18–30 low, reclined, visible teeth increasingly reduced towards the finger base, reaching back almost to sb; proximal 2–7 teeth between sb and b completely obsolete, only detectable by presence of dental canals; coupled sensilla pc usually closer to sb than to st, but sometimes reaching halfway between sb and b or closer to st than to sb; tip of movable finger with apical sensilla am1 ‾ 2; trichobothria as in Figs 18–19, 23–31, ist usually distad of the line eb/esb; ratio of movable finger/ hand of chela usually 1.8–1.9, rarely 1.7 or 2.0 (♂), usually 1.6–1.7, rarely 1.8 to 2.0 (♀); ratio of pedipalpal femur/ movable finger 1.0–1.1 (♂♀); ratio of pedipalpal femur/carapace 1.3–1.4 (♂♀).

Measurements (in mm). Body length 1.3–1.7 (♂) or 1.5–2.0 (♀). Carapace 0.40–0.50 × 0.42–0.51 (0.38–0.48 anteriorly) (♂) or 0.40–0.60 × 0.41–0.60 (0.39–0.58 anteriorly) (♀). Chelicera 0.35–0.46 × 0.16–0.21 (♂) or 0.38–0.56 × 0.19–0.26 (♀); movable finger length 0.18–0.24 (♂) or 0.20–0.29 (♀). Pedipalp: femur 0.51–0.69 × 0.09–0.13 (♂) or 0.50–0.84 × 0.105–0.14 (♀); chela 0.73–1.02 × 0.14–0.20 (♂) or 0.76–1.27 × 0.16–0.28 (♀); hand length 0.23–0.36 (♂) or 0.26–0.45 (♀); fixed finger length (from tip to eb) 0.48–0.67 (♂) or 0.50–0.80 (♀); movable finger length 0.48–0.66 (♂) or 0.50–0.76 (♀).

Description of tritonymph. Integument weakly pigmented, hispid granulation less marked than in adults. Carapace 0.95–1.05 times longer than broad, form of anterior margin as in adults; four developed eyes; chaetotaxy m 4m:6:4:2:m 2m (22). Chaetotaxy of tergites as in adults. Chaetotaxy of sternites II–X 5:(2)6–8(2):(1)6(1):7–8:6:6:6:6:7. Chelicera 2.0–2.1 times as long as broad, palm with 5 setae and 2 microsetae laterally; fixed finger with 7–8 teeth, the first two larger, the following proximally reduced in size; movable finger with an isolated subapical tooth (di) and 6–9 teeth; gl ratio 0.54–0.58; spinneret prominent and apically rounded as in females; rallum with 9 blades; serrula exterior with 13–14 blades. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 2 marginal microsetae, II 4, III 5, IV 5; coxa II with 4–8 (usually 5) coxal spines, coxa III with 2–5 (usually 3) coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 4.5–4.8 times as long as broad; chela 4.9–5.2 times as long as deep; hand of chela 1.7–1.8 times as long as deep; fixed finger with 22–31 reclined teeth with dental canals, without intercalary microdenticles; first distal reduced tooth distad of trichobothria dx, 3–6 proximal teeth low, with rounded tips; base of fixed finger with 3–4 microtubercles; base of fixed finger usually with few microtubercles; fixed finger at level of it/est with 4–6 teeth occupying 0.1 mm (distance between successive apices 0.017–0.024 mm); distal paraxial seta gradually curved and thin; movable finger with 18–25 low, reclined, teeth increasingly reduced towards the finger base, reaching back almost to b, followed by 2–3 completely obsolete proximal teeth, revealed only by the presence of dental canals; coupled sensilla pc halfway between st and b; ratio of movable finger/hand of chela 1.7–1.9; ratio of pedipalpal femur/movable finger 1.0–1.1; ratio of pedipalpal femur/carapace 1.0–1.1.

Measurements (in mm). Body length 1.0–1.4. Carapace 0.38–0.42 × 0.39–0.42. Chelicera 0.31–0.37 × 0.15–0.17, movable finger length 0.16–0.18. Pedipalp: femur 0.41–0.48 × 0.08–0.10; chela 0.61–0.72 × 0.12–0.14; hand length 0.21–0.25; fixed finger length (from tip to eb) 0.38–0.45; movable finger length 0.38–0.46.

Remarks. Chthonius heterodactylus was described by Tömösváry (1882) from three specimens, of unstated sex, from as many localities: Bártfa (now Bardejov, Slovakia), Szinnaikő (now Sninský kameň, Slovakia) and Zilah (now Zalǎu, Romania). Harvey (1991) gave the type localities as being “several localities in Hungary ”, but as noted by Ducháč et al. (2007), Bardejov and Sninský kameň are located in modern Slovakia. Harvey (2013) accordingly corrected the listing of the type localities, but again overlooked that of Zalǎu, Romania.

The original description and drawings show an eyed Chthonius (Chthonius), 2.2 mm long, with a reduced epistome, sigmoid fixed chelal finger and a prominent spinneret; Tömösváry’s figs 1 and 2 are probably drawn from a female, judging from the chelal shape. The syntypes are not in HNHM and are very probably lost (L. Dányi in litt., 7.I.2014), as are most of the myriapodological types of Tömösváry’s species (Korsós 2003).

Daday (1889a, b) synonymized C. heterodactylus with C. tetrachelatus, following the examination of a specimen (syntype) from “Sinnaikő” used by Tömösváry (1882) in describing C. heterodactylus. Although this specimen, labelled “St. 613/61” (Daday 1889a, b), is no longer in HNHM (L. Dányi in litt., 7.I.2014), this synonymy cannot be accepted because, as noted by Hadži (1930), the species described and illustrated as C. heterodactylus by Tömösváry (1882) is clearly not C. (Ephippiochthonius) tetrachelatus. Beier (1928) listed C. heterodactylus as a doubtful synonym of C. cavernarum, but this was rejected by Hadži (1930), as well as by Beier (1932) himself, when he treated C. heterodactylus as a species inquirenda of the genus Chthonius. The supposedly straight shape of the fixed chelal finger, as reported by Beier (1932) (“Fester Palpenfinger gerade”), is presumably based on Tömösváry’s drawings, which show the pedipalps in sublateral view, with fixed chelal finger appearing straight. C. heterodactylus was finally redescribed by Beier (1939a, 1963), based on specimens of both sexes from three localities in Romanian Transylvania, but this concise description lacks information about setal disposition around the male genital opening and no comparison with other species was attempted. Subsequent authors (see Harvey 2013) chiefly contributed faunistic data for C. heterodactylus, with sporadic additions of morphometric data (Kárpáthegyi 2006; Ducháč et al. 2007; Christophoryová et al. 2011b).

Chthonius diophthalmus was described by Daday (1889a), based on two specimens—males, as subsequently stated by Mahnert (1978) —from Mehádia (now in Romania), previously attributed to C. rayi by Tömösváry (1882). Beier (1932) listed C. diophthalmus among the species inquirendae (“Unsichere Arten”) of the genus Chthonius, with a diagnosis derived from the descriptions of Tömösváry (1882) and Daday (1889a), though at the same time he suggested that it was probably a synonym of C. ischnocheles (Hermann, 1804). Beier (1935) described C. orthodactylus gracilis from specimens, presumably of both sexes (“einige semiad. ♂♂ und ♀♀”), from Sinaia, Romania, highlighting, among other characters, the presence of scattered setae on each side of the male genital opening. C. orthodactylus gracilis was subsequently synonymized with C. diophthalmus by Beier (1939a). Hadži (1939) described C. ksenemani from specimens of both sexes from Pop Ivan (now in Ukraine), giving details of variability in chaetotaxy and sexually dimorphic characters, emphasizing the presence of scattered setae on each side of the male genital opening. He compared the species to C. orthodactylus gracilis. C. ksenemani was subsequently reported by Beier (1963) and Krumpál & Kiefer (1981), but later synonymized with C. diophthalmus by Schawaller (1989). C. diophthalmus was at last redescribed by Beier (1939a, 1963) from specimens of both sexes from eleven close localities in Romanian Transylvania; three of these localities (Turda Jara, Turda Câmpeni and Bihor Beius) were shared with C. heterodactylus. Beier’s redescription emphasized sexually dimorphic characters (i.e. shape of epistome, of chelal hand and dentition of fixed chelal finger) and the presence of scattered setae on each side of the male genital opening; no comparison was made with other species. Examination of the male syntypes of C. diophthalmus allowed Mahnert (1978) to draw the pedipalpal chela, with details of the distal dentition of the fixed and movable fingers. Subsequent authors (see Harvey 2013) chiefly provided faunistic data concerning C. diophthalmus, with sporadic additions of morphological (Schawaller 1989, Christophoryová et al. 2011b) or karyological data (Šťáhlavský & Kral 2004). The current interpretations of C. heterodactylus and C. diophthalmus, mostly follow Beier (1939a) and, for C. diophthalmus, Mahnert (1978) and Schawaller (1989).

Comparison of the male syntypes of C. diophthalmus from Mehádia (Romania) (Figs 20–23) and males from localities of Vihorlat Mountains, very close to Sninský kameň (Slovakia) (Figs 12–19), here attributed to C. heterodactylus, reveals that they are identical in most morphological characters (carapacal chaetotaxy, presence of epistome, shape of pedipalpal chela, dentition of chelal fingers and presence of scattered setae on each side of male genital opening). The only noteworthy difference is the absence of a cheliceral spinneret in the syntypes of C. diophthalmus. However, the spinneret can vary in size, from more or less prominent to absent, even between males of the same population [Turda, Jara, 7.VI.1938, R. Leruth (552); Turda, Câmpeni, 17.VII.1938, R. Leruth leg. (R61A) (IRSNB): Figs 32–33].

Examination of most of the specimens from Romanian Transylvania used by Beier (1939a) in his redescription of C. diophthalmus revealed the unexpected presence of C. hungaricus Mahnert, 1981 at five localities, being syntopic with C. diophthalmus at two of these. The question of whether the female chela represented in Beier (1939a: 3, fig. 1) may belong to C. hungaricus, as suggested by the close dentition of the fixed finger, has not been solved, since the specimen was not found in any of the vials. In any case, the specimens studied by Beier (1939a) show strong sexual dimorphism in their dimensions and the shape of pedipalpal chelae, a high variability in the dentition of the fixed and movable chelal fingers (Figs 27–31) and the scattered arrangement of setae on each side of male genital opening.

Assuming that populations from the Vihorlat Mountains belong to C. heterodactylus, and having determined the conspecificity of males from this and other localities with the syntypes of C. diophthalmus, the following synonymies are proposed: Chthonius diophthalmus Daday, 1889 is a junior subjective synonym of C. heterodactylus Tömösváry, 1882 (n. syn.) and, consequently, C. (C.) orthodactylus gracilis Beier, 1935 and C. (C.) ksenemani Hadži, 1939 are junior subjective synonyms of C. heterodactylus (n. syn.).

Chthonius leruthi was described by Beier (1939a) from four females from Turda, Jara and Cluj, Romania, syntopic with C. heterodactylus. Beier (1939a) compared C. leruthi with C. heterodactylus, from which it differs in being larger and in having a different dentition of the fixed chelal finger: movable finger length 0.75 mm in C. leruthi, 0.64–0.66 mm in C. heterodactylus (♀); fixed finger with 15–16 teeth in C. leruthi, with 24–25 teeth in C. heterodactylus (♀) (Beier 1939a). Examination of the syntype females of C. leruthi shows that they are simply large specimens of C. heterodactylus. Chthonius (Chthonius) leruthi Beier, 1939 is there considered here to be a junior subjective synonym of C. (C.) heterodactylus Tömösváry, 1882 (n. syn.). The above redescription of C. heterodactylus includes meristic and metric data from the type specimens of C. leruthi.

Chthonius heterodactylus is an epigean species known from the Western Sudetes (Germany) to Southern Carpathians (Romania), through the whole Carpathian range (Fig. 90). Among the species of Chthonius of the C. heterodactylus group, C. heterodactylus seems to be related to the epigean C. hungaricus from Hungary, Romania and Slovakia. Differences between C. heterodactylus and C. hungaricus are given in the above key.