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

Allegue, Maite, Peralta-Seen, Nicolás & Ferretti, Nelson, 2025, Integrative systematics of the tarantulas Euathlus Ausserer, 1875 from Argentina: cladistics, molecular phylogeny and new species (Araneae: Theraphosidae), Arthropod Systematics & Phylogeny 83, pp. 713-736 : 713-736

publication ID	https://doi.org/10.3897/asp.83.e171040
publication LSID	lsid:zoobank.org:pub:90DE5EC9-FEFB-4E43-B496-FDD96A39B50C
DOI	https://doi.org/10.5281/zenodo.17866504
persistent identifier	https://treatment.plazi.org/id/76F07C38-F617-5A42-82C3-0D602CED2CE9
treatment provided by	Arthropod Systematics & Phylogeny by Pensoft
scientific name	Euathlus susanae
status	sp. nov.

Treatment

3.3. 4. Euathlus susanae sp. nov. Peralta-Seen, Allegue and Ferretti

Figures 12 View Figure 12 , 13 View Figure 13 , 14 View Figure 14 , 15 View Figure 15 , 18 View Figure 18 , Tables 5 View Table 5 , 6 View Table 6

Type material.

Holotype: ARGENTINA • 1 ♂; La Pampa, Chical Co Department, Reserva Provincial Cerro Negro ; 36.0569°S 68.2816°W; 1141 m a. s. l.; 21 Oct. 2022; G. San Blas, F. Diez and N. Peralta-Seen leg.; UNS M 1078 GoogleMaps . Paratype: ARGENTINA • 1 ♀; La Pampa, Chical Co Department, Reserva Provincial Cerro Negro ; 36.0566°S 68.2830°W; 1166 m a. s. l.; 20 Oct. 2022; N. Peralta-Seen leg.; UNS M 1396 GoogleMaps .

Other material.

ARGENTINA • 1 ♂; La Pampa, Chical Co Department, Reserva Provincial Cerro Negro ; 36.0574°S 68.2831°W; 1165 m a. s. l.; 21 Oct. 2022; G. San Blas, F. Diez and N. Peralta-Seen leg.; UNS M 1068 GoogleMaps . • 2 ♀♀; Mendoza, Malargüe Department, Agua Escondida ; 36.1538°S 68.2974°W; 20–22 Oct. 2022; N. Peralta-Seen leg.; UNS M 1493 , M 1509 View Materials GoogleMaps .

Diagnosis.

Euathlus susanae sp. nov. can be distinguished from all known congeners by the following combination of characters: tibial apophysis with two robust branches, the PB shorter than the RB and both bearing strong internal spines, males with a palpal organ similar in general morphology to that of E. condorito , but it can be distinguished by a more developed prolateral inferior keel ( PI) with stronger and distally serrated teeth (Figs 12 D View Figure 12 , 13 View Figure 13 ). Females are diagnosed from congeners by their spermathecae, which consist of two wide seminal receptacles projecting straight upward, each with pronounced inner lobes and two large semi-spheroid lateral chambers pointing upwards (Fig. 14 D, E View Figure 14 ).

Description male.

Male holotype ( UNS M 1078 ). — Coloration ( in alcohol): carapace dark brown with small grey and black setae and long golden setae more abundant on the margins and on dorsal chelicerae (Fig. 12 A View Figure 12 ); legs brownish; abdomen with black setae and long orange setae and a large patch of orange setae on the anterior-dorsal face; sternum, coxa, and trochanter reddish (Fig. 12 B, C View Figure 12 ). — Coloration ( in life): Orange hairs on legs, margins of carapace, chelicerae, and proximal abdomen. Ventral body with dark brown / black coloration (Fig. 15 D, E View Figure 15 ). Total length 28.97. — Prosoma: Carapace length 12.32, width 11.32. Anterior eye row slightly procurved, posterior one recurved. Eye sizes and interdistances: AME 0.31, ALE, 0.59, PME 0.34, PLE 0.56, AME - AME 0.31, AME - ALE 0.19, PME - PME 0.75, PME - PLE 0.13, ALE - PLE 0.19, OQ length 1.41, width 1.75, clypeus 0.31. Fovea transverse, straight, width 1.33. Labium length 1.56, width 2.06, with 76 cuspules. Maxillae (right / left) 144 / 151 cuspules. Sternum length 6.11, width 5.55 (Fig. 12 B View Figure 12 ). Right chelicerae with 7 well-developed teeth on promargin of furrow and 9 small teeth on the proximal area of furrow, left chelicerae with 7 well-developed teeth and 1 small located distally on the promargin of furrow and 9 small teeth on the proximal area of furrow. — Appendages: Tarsi I – IV densely scopulated, undivided. Metatarsi I fully scopulated, II 1 / 2 scopulated, III 1 / 3, IV 1 / 4 apically scopulated. Leg and palpal segments lengths in Table 5 View Table 5 . Spination: Femora and patellae of palps and legs I – IV, tarsi of palp and legs I – IV, 0. Femora: II 1-3 - 1 P, III 1-1 - 1 - 1 P. Tibiae: palp 2-2 V, 1-2 P; I 2-1 - 1 V, 1-1 P; II 3-2 - 3 V, 1-1 P; III 2-2 - 3 V, 1-1 P, 1-1 R; IV 2-2 - 2 V, 1-1 P, 1 R. Metatarsi: I 1-1 V; II 1 V; III 1-1 - 2 V, 1-1 - 1 P, 1-1 - 1 R; IV 1-1 - 1 V, 1-1 - 1 - 1 P, 1-1 R. Metatarsus I slightly curved. Tibial apophysis of legs I with two short well-developed branches, retrolateral branch slightly longer than prolateral; PB and RB with an internal subapical strong and short spine (Fig. 12 D View Figure 12 ). Metatarsi I flexes to the retrolateral branch of the tibial apophysis. — Opisthosoma: Abdomen with oval central urticating setae patch with types III and IV. Four spinnerets, PMS 1.1 long and PLS three segmented, basal segment 2.1 long, medial segment 1.2 long and apical segment 1.5 long. — Genital organs: Palpal organ piriform without constriction between tegulum and embolus. Embolus curving retrolaterally, prolateral keels unequal; PS flat and less developed, PI well developed with 6–9 small teeth along the retrolateral face of the curvature of embolus (Fig. 13 View Figure 13 ).

Description female.

Female paratype ( UNS M 1396 ). — Coloration ( in alcohol): Carapace dark brown covered with black and grey short hairs and golden long hairs which are more abundant on the margins and on dorsal chelicerae (Fig. 14 A View Figure 14 ), legs brownish with evident patellar lines, abdomen dark brown with short black hairs and long golden hairs on the dorsum; sternum, coxa and trochanter light brown (Fig. 14 B, C View Figure 14 ). — Coloration ( in life): Iridescent orange to pink hairs at the base of the legs, chelicerae, and carapace. Longer pink hairs on the legs, margins of the carapace, and distal abdomen. The proximal abdomen is covered with long orange hairs. The ventral face of body is very dark, almost black (Fig. 15 C, E View Figure 15 ). Total length 36.63. — Prosoma: Carapace length 13.88, width 12.65. Anterior eye row procurved, posterior one recurved. Eye sizes and interdistances: AME 0.31, ALE 0.63, PME 0.41, PLE 0.50, AME - AME 0.47, AME - ALE 0.13, PME - PME 0.88, PME - PLE 0.13, ALE - PLE 0.19, OQ length 1.47, width 2.09, clypeus 0.34. Fovea transverse, straight, width 1.35. Labium length 1.67, width 2.78 with 125 cuspules. Maxillae (right / left) with 137 / 139 cuspules. Sternum length 8.33, width 6.66 (Fig. 14 B View Figure 14 ). Right chelicerae with 8 large teeth on promargin of furrow and 6 small teeth on the proximal area of furrow, left chelicerae with 7 large teeth on the promargin of furrow and 6 small teeth on the proximal area of furrow. — Appendages: Tarsi I – IV densely scopulated, undivided. Metatarsi I 3 / 4 scopulated, II 2 / 3 scopulated, III 1 / 3 scopulated, IV 1 / 4 apically scopulated. Legs and palpal segments lengths in Table 6 View Table 6 . Spination: Femora and patellae of legs I – IV, patellae of palps, 0. Femora of palp: 1 P. Tibiae: palp 2-2 - 3 V, 1 R; I 2 V; II 1-2 V; III 2-1 - 2 V, 1 P; IV 2-2 V, 1- 1 P. Metatarsi: I 1 V; II 1-1 V; III 2-1 - 2 V, 1-1 - 1 P, 1-1 - 1 R; IV 1-1 - 2 - 3 V, 1-1 - 1 - 1 P, 1-1 R. — Opisthosoma: Abdomen with large “ apple ” shaped urticating setae patch with types III and IV. Four spinnerets, PMS 1.2 long and PLS three segmented, basal segment 2 long, medial segment 1.6 long, and apical segment 1.3 long. — Genital organs: Spermatheca with wide seminal receptacles, upper margin smooth, with pronounced oval margins towards the inner part, and with two semi-spheroid lateral chambers pointing upwards (Fig. 14 D, E View Figure 14 ).

Etymology.

This species is a noun in the genitive case, named after Susana Seen, the mother of the collector, whose unconditional support made the discovery of this species possible.

Distribution and natural history.

This species is distributed in northwestern La Pampa province and southeastern Mendoza province. Euathlus susanae sp. nov. was found in the Protected Provincial Area Cerro Negro, La Pampa province (Fig. 15 A View Figure 15 ), and in the locality of Agua Escondida, Mendoza province (Fig. 18 View Figure 18 ). The Cerro Negro reserve contains the “ Cerro Negro ”, which is a basaltic volcano dated from 4.71 Ma that elevates 1167 m a. s. l. and its summit represents the highest geographical point in La Pampa province ( Bertotto et al. 2022). The volcano is surrounded by a middle altitude steppe, located in the center of the Monte biogeographical province (elevation of about 1100 m), which is dominated by Larrea divaricata Cav. 1800 . The specimens of Euathlus susanae sp. nov. were found in burrows and shelters under vesicular volcanic agglomerates. One adult female and two immature males were found in October (spring in the southern hemisphere). The immature males molted three months after capture, in late February (summer in the southern hemisphere). Individuals from Agua Escondida (Fig. 15 B View Figure 15 ), were found in burrows and shelters under rocks of the Agua Escondida Formation, composed by quartz sandstones of Upper Carboniferous age (elevation of about 1095 m) ( González Díaz 1972), also located in the Monte biogeographical province.

Sexual behavior.

We observed two mating events in Euathlus susanae sp. nov. One event was performed by a male and a female from Cerro Negro Reserve, La Pampa province. The courtship was initiated by the male, who performed rhythmic leg tapping with legs I and vibrations with leg III, lasting a total of 11 minutes. The male then approached the female, making contact toward her front legs with his legs I and II. After that, the female oriented to the position of the male while performing high-frequency leg tapping with legs I and palps over the substrate. The male repeated leg tapping with legs I, prompting the female to approach. The male then grasped his first pair of legs around the female’s chelicerae and elevated her to access the genital opening. Once the female was lifted, the male performed palpal boxing (alternating vertical movements of the pedipalps in contact with the female’s sternum). A single palpal insertion event was observed, lasting about 47 seconds. After disengagement, the male performed leg tapping with legs I on the female, but she walked away.

In the second event, a male from Cerro Negro, La Pampa and a female from Agua Escondida, Mendoza successfully mate. The male initiated courtship by vibrating leg III, followed by leg tapping with legs I, or with legs I and II simultaneously. This courtship phase lasted 4.16 minutes, during which the male approached the female slowly while continuing these displays. Upon reaching the female, the male tapped her leg IV (as she was oriented in the opposite direction), causing her to turn towards him. He attempted to grasp the tibial apophysis on her chelicerae, but the female became unstable, preventing clasping. The male initiated the courtship again for an additional 5.21 minutes, performing leg tapping, after which the female approached. At this instance, the male successfully clasped the tibial apophysis into the chelicerae of the female and then elevated her. The copulation event lasted 4.1 minutes. The male began with palpal boxing, followed by insertion of the right palp for approximately 0.6 minutes. He then attempted an insertion of the left palp but was unsuccessful, after trying again, the left palp was successfully inserted for 1 minute. After, he performed a second left palp insertion, which lasted 1.85 minutes. After disengagement, the male performed leg tapping on the female’s front legs; after this movement, the female turned away.