Euathlus basalticus, Allegue & Peralta-Seen & Ferretti, 2025

3.3. 2. Euathlus basalticus sp. nov. Allegue and Ferretti

Figures 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 18 View Figure 18 , Tables 1 View Table 1 , 2 View Table 2

Type material.

Holotype: ARGENTINA • 1 ♂; Neuquén, Ñorquín Department, Caviahue ; 37.9297°S 71.0449°W; 13 Nov. 2023; Allegue, Bambozzi, Nicoletta, Panchuk and Schwerdt leg.; UNS M 1122 GoogleMaps . Paratype: ARGENTINA • 1 ♀; Neuquén, Ñorquín Department, Caviahue, near Salto del Agrio waterfall ; 37.8193°S, 70.8992°W; 12 Nov. 2023; Allegue, Bambozzi, Nicoletta, Panchuk and Schwerdt leg.; UNS M 1492 GoogleMaps .

Other material.

ARGENTINA • 1 ♀; Neuquén, Ñorquín Department, Copahue ; 37.7964°S 71.1167°W; 25 Mar. 2009; R. Sage leg.; MACN -Ar 32688 GoogleMaps . • 1 ♀; Neuquén, Caviahue ; Feb. 1968; E. Maury leg.; MACN -Ar 38155 . • 1 ♀; Neuquén, Ñorquín Department, near Copahue ; 37.8189°S 71.0987°W; 3 Feb. 2001; G. Cheli leg.; CNP-CE 1508 GoogleMaps . • 1 ♂; Neuquén, Ñorquín Department, near Caviahue ; 37.8500°S 71.0116°W; 1658 m a. s. l.; 6 Jan. 2017; D. Ferraro leg.; MACN -Ar 37941 GoogleMaps .

Diagnosis.

Euathlus basalticus sp. nov. can be distinguished from all known congeners by a unique combination of characters in males: a dark tibial apophysis with two robust branches, the PB shorter than the RB and bearing a strong internal basal spine, while the RB has a prominent internal subapical spine (Fig. 4 C – E View Figure 4 ), palpal organ piriform (Fig. 5 View Figure 5 ) embolus arises gradually from the tegulum, without a distinct junction, presence of 1–2 small teeth at the tip of the prolateral inferior keel. Females can be distinguished from congeners (except from E. condorito ) by having two wide seminal receptacles, rounded at the upper margin. Each receptacle bears a large semi-spheroid lateral chamber connected by a constricted duct and projecting from the lower outer margin. In addition, females differ from those of E. condorito in the orientation of the lateral chamber, which has its longest axis parallel to the lateral margin of the seminal receptacle (Fig. 6 D – F View Figure 6 ).

Remarks.

The female MACN -Ar 32688 listed above in other material of Euathlus basalticus sp. nov. had previously been designated as the paratype of Euathlus tenebrarum by Ferretti (2015). However, based on morphological examination, we found that this female is not conspecific with the male of E. tenebrarum . Our assignment to E. basalticus sp. nov. is based on diagnostic morphological differences observed in female specimens from the MACN collection, collected in localities near the type locality of E. tenebrarum . Moreover, the type locality of E. tenebrarum , Lago Curruhué Chico, is about 237 km distant from Copahue, where specimen MACN -Ar 32688 was collected.

Description male.

Male holotype ( UNS M 1122 ). — Coloration ( in alcohol): Carapace brown, abdomen dark brown, lighter lines on dorsal femur, patellae and tibiae of palps and legs I – IV, maxillae and labium yellow, dark yellow sternum (Fig. 4 A, B View Figure 4 ). — Coloration ( in life): Legs I – IV and palps with light longitudinal lines on the dorsal surface of femora, patellae, and tibiae. Legs covered with long yellowish hairs (Fig. 7 D View Figure 7 ). Whitish setae present on the margins of the cephalothorax and the proximal area of the chelicerae. Abdomen with reddish hairs anteriorly and yellowish hairs posteriorly. Spinnerets covered with orange hairs. Total length 18.07. — Prosoma: Carapace length 9.08, width 8.95. Anterior eye row procurved, posterior one recurved. Eye sizes and interdistances: AME 0.15, ALE 0.39, PME 0.24, PLE 0.25, AME - AME 0.30, AME - ALE 0.11, PME - PME 0.52, PME - PLE 0.07, ALE - PLE 0.22, OQ length 0.88, width 1.26. Clypeus 0.12. Fovea transverse, short, deep, slightly procurved, width 0.89. Labium length 1.12, width 1.56, with 65 cuspules. Maxillae (right / left) with 118 / 120 cuspules. Sternum length 4.44, width 3.58 (Fig. 4 B View Figure 4 ). Chelicerae with 7 large teeth on promargin of furrow and 10 small teeth on the proximal area of retromargin. — Appendages: Tarsi I – IV densely scopulate with scopula entire, undivided. Metatarsi I 2 / 3 scopulated, II 1 / 2 scopulated, III 1 / 3 scopulated, IV 1 / 4 apically scopulated. Leg and palpal segments lengths in Table 1 View Table 1 . Spination: Patellae of legs II – IV, femur of legs I and IV, tarsi of palps and legs I – IV, 0. Femora: palp 0-0 - 0 - 1 P; II 0-0 - 1 - 2 P; III 0-0 - 0 - 1 P, 0-1 - 1 - 1 R. Patellae: palp 0-0 - 1 - 0 P; I 0-0 - 0 - 1 V. Tibiae: palp 2-2 - 0 - 0 V, 0-1 - 0 - 0 P; I 2-0 - 2 - 0 V, 0-1 - 0 - 1 P, 1-0 - 0 - 0 R; II 2-2 - 0 - 4 (ap) V, 0-1 - 0 - 1 P, 1-1 - 0 - 0 R; III 1-1 - 0 - 4 (ap) V, 1-2 - 1 - 0 P, 1-2 - 1 - 0 R; IV 2-3 - 1 - 4 (ap) V, 0-1 - 0 - 1 P, 0-2 - 1 - 0 R. Metatarsi: I 1-0 - 0 - 1 V; II 1-1 - 0 - 1 (ap) V; III 2-1 - 1 - 3 (ap) V, 1-0 - 1 - 1 P, 1-1 - 0 - 1 R; IV 2-0 - 2 - 3 (ap) V, 1-0 - 1 - 1 P, 0-2 - 1 - 1 R. Metatarsus I straight. Tibial apophysis of leg I dark with two short branches, RB slightly longer than prolateral, both well-developed and originating from a common base, PB with a basal internal short strong spine, RB with a subapical internal short strong spine (Fig. 4 C – E View Figure 4 ). Metatarsus I rests retrolaterally on the tibial apophysis when flexed. — Opisthosoma: Abdominal urticating setae patch large, reniform and central, with only type III urticating setae. Four spinnerets, PMS 0.7 long and PLS three segmented, basal segment 0.9 long, medial segment 0.8 long, and apical segment 1.2 long. — Genital organs: Palpal organ piriform, with a relatively broad embolus that tapers distally. The embolus is long and curved retrolaterally. Prolateral keels are unequally developed, with PI more developed than PS. The PI bears one or two well-developed teeth, located distally on the embolus but not entirely at the apex. An apical keel is also present (Fig. 5 View Figure 5 ).

Description female.

Female paratype ( UNS M 1492 ). — Coloration ( in alcohol): carapace brown, margins of carapace yellow, yellowish lines on dorsal femur, patellae and tibiae of palps and legs I – IV, abdomen dark brown (Fig. 6 A View Figure 6 ). — Coloration ( in life): hole body reddish. Legs I – IV and palps exhibit distinct light longitudinal lines on the dorsal surfaces of the femora, patellae, and tibiae. Legs and abdomen are densely covered with long yellowish hairs. Margins of carapace, the base of the legs, and the proximal area of the chelicerae are light brown. Patch of urticating setae yellow (Fig. 7 C View Figure 7 ). Total length 15.60. — Prosoma: Carapace length 6.52, width 6.18. Anterior eye row procurved, posterior one recurved. Eye sizes and interdistances: AME 0.12, ALE 0.34, PME 0.19, PLE 0.25, AME - AME 0.28, AME - ALE 0.11, PME - PME 0.47, PME - PLE 0.07, ALE - PLE 0.12, OQ length 0.96, width 1.14. Clypeus 0.12. Fovea transverse, short, deep, slightly procurved, width 0.41. Labium length 0.91, width 1.31 with 52 cuspules. Maxillae (right / left) with 107 / 103 cuspules. Sternum length 3.37, width 3.24 (Fig. 6 B View Figure 6 ). Chelicerae with 9 well-developed teeth on promargin of furrow and 3 small teeth on the proximal area of retromargin. — Appendages: Tarsi I – IV densely scopulate, undivided. Metatarsi I 3 / 4 scopulated, II 1 / 2 scopulated, III 1 / 3 scopulated, IV 1 / 4 apically scopulated. Legs and palpal segments length in Table 2 View Table 2 . Spination: Femora of legs I – IV, patellae and tarsi of palp and legs I – IV, 0. Femora: palp 0-0 - 0 - 1 P. Tibiae: palp 1-1 - 1 - 3 (ap) V; I 0-1 - 0 - 0 V, 0-0 - 0 - 1 (ap) P; II 0-0 - 0 - 3 (ap) V; III 0-2 - 0 - 3 (ap) V, 0-1 - 1 - 0 P, 0-0 - 1 - 0 R; IV 0-1 - 0 - 2 (ap) V, 0-1 - 1 - 1 P, 0-2 - 0 - 1 R. Metatarsi: I 0-1 - 0 - 1 (ap) V; II 0-1 - 0 - 1 (ap) V; III 2-2 - 0 - 3 (ap) V, 1-1 - 0 - 1 P, 0-1 - 0 - 0 R; IV 1-2 - 1 - 4 (ap) V, 0-1 - 0 - 1 P, 1-2 - 1 - 1 R. — Opisthosoma: Abdominal urticating setae patch large, reniform and central, with types III and IV present. Four spinnerets, PMS 0.74 long and PLS three segmented, basal segment 1.07 long, medial segment 0.62 long, and apical segment 0.82 long. — Genital organs: Spermatheca with two wide seminal receptacles with rounded shape facing upwards, each with a semi spheroid chamber pointing laterally, connected with a constricted duct, projecting from the lower outer margin of each receptacle (Fig. 6 D View Figure 6 ).

Etymology.

The specific name “ basalticus ” is a Latin adjective in the nominative singular. It refers to the strong association of this species with basaltic substrates, as specimens were exclusively found in areas dominated by basaltic rock formations. The name is derived from the Latin “ basaltes ” with the suffix “ - icus, ” meaning “ belonging or pertaining to. ”

Distribution and natural history.

These spiders are found in rocky formations (Fig. 7 View Figure 7 ). These spiders inhabit rocky outcrops composed of andesitic and basaltic-andesitic lavas typical of the Caviahue – Copahue volcanic complex. They occur at elevations exceeding 1 600 m a. s. l., reaching near the summit of Copahue volcano at nearly 3 000 m a. s. l. ( Varekamp et al. 2016). The lower montane zone shows the highest plant diversity due to abundant precipitation and moderate thermal conditions, with climax vegetation corresponding to Nothofagus forests and thickets mixed with the conifer Araucaria araucana (Mol.) Koch. , which has its northernmost distributional limit in Argentina within this park. Key bioindicator species of the shrub-grass steppe ecotone include Festuca scabriuscula Philippi , Berberis empetrifolia Lamarck , and Ephedra frustillata Miers , creating the complex Andean-Patagonian ecosystem ( Gandullo et al. 2004). Andesite and basaltic andesite are the predominant rock types of this basin ( Cabrera et al. 2020) (Fig. 18 View Figure 18 ).