Actinopus chilikuti, Ríos-Tamayo & Goloboff, 2025

Actinopus chilikuti sp. nov.

( Figs 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Actinopus septemtrionalis Ríos-Tamayo & Goloboff, 2018: 26 View in CoL View Cited Treatment (only female from Formosa province). Misidentification.

Holotype. ARGENTINA: Santiago del Estero Prov: 1 ♂ ( FML-ARAN 02273 ) from Parque Nacional “Copo” , seccional La Portada (25°58’21.15”S 61°57’30.68”W), 23 November 2023, Ríos-Tamayo. D & P. Goloboff leg. GoogleMaps Paratypes. Same data as holotype, 1 ♀ ( FML-ARAN 02274 ), 24 November 2023, Ríos-Tamayo. D & J.C Stazonelli leg. GoogleMaps ; 3 ♂♂ ( FML-ARAN 02275 ), 23 November 2023, Ríos-Tamayo. D, J.C Stazonelli & P. Goloboff leg. GoogleMaps

Other material examined. ARGENTINA: Formosa Prov: 1 ♀ ( MACN-Ar 27307 ), tissue sample ( MACN-Ar 27307-t1 ) from Reserva Natural Formosa : Seccional Rio Teuco, (24°18’0.25”S 61°48’5.41”W), 27 June–5 July 2010, Izquierdo. M, Kopuchian. C and Calderón. L. leg. GoogleMaps

Etymology. The specific epithet works as a noun in apposition referring to the small size of the specimens of this species. In Quechua Aymara (very commonly spoken in Santiago del Estero), ch’ilikuti means “little, small”.

Diagnosis. Members of Actinopus chilikuti sp. nov. are small spiders. Males can be distinguished from all other species with Type I morphology in Argentina by having a copulatory bulb with a more curved embolus ( Figs 2C–F View FIGURE 2 , 4C View FIGURE 4 ), with keels well developed (similar to A. reycali ) and PA developed (smaller in A. reycali , and A. clavero but bigger in A. septemtrionalis , Fig 4 View FIGURE 4 ). Females can be differentiated from A. reycali and A. septemtrionalis by the shorter and more slender spermathecae ( Fig 3D View FIGURE 3 , similar to A. clavero ). It is distinguished from A. clavero by a larger number of retrolateral thorns on tibia II (30 vs 20, Fig 3G View FIGURE 3 ) and fewer on tibia I (0 vs 5).

Description. Male holotype (FML-ARAN 02273). Total length: 6.61. Carapace ( Fig 1A View FIGURE 1 ): length 3.30, width 2.93; cephalic region: length 1.89, width 2.01; clypeus small, 7 bristles between PME, 4 behind each PME–PLE. Fovea: length 0.44, width 0.80. Eyes, diameters and interdistances ( Fig 1C View FIGURE 1 ): AME 0.19 (large), ALE 0.27, PME 0.14, PLE 0.16, ocular group length 0.54, anterior width 1.32, 1.23 posterior width; AME–ALE 0.20, PME–PLE 0.06, AME–PME 0.19, ALE–PLE 0.19, AME–AME 0.09, PME-PME 0,74. Chelicerae: apex with 7 recumbent and elongated bristles over fang base. Rastellum with 4 marginal blunt spines and 2 small dorsal ones. Cheliceral furrow with 4 large promarginal and 5 retromarginal teeth and 4 denticles, near promarginal teeth. Labium ( Fig 1B View FIGURE 1 ): length 0.52, width 0.55. Maxillae ( Fig 1B View FIGURE 1 ): anterior length 0.78, posterior length 1.18, width 0.78. Sternum ( Fig 1B View FIGURE 1 ): Center flat, length 2.15, maximum width 1.66, minimum width 0.87. Postlabial sigilla square, posterior sigilla small and well defined. Abdomen ( Fig 1E, F View FIGURE 1 ): length 2.99, covered by small bristles. PMS: length 0.32; PLS: length of basal:medial:apical segments 0.38:0.17:0.13. Lengths of legs and palp: I: 3.92, 1.46, 2.52, 2.83, 1.60, 12.33. II: 3.70, 1.40, 2.40, 2.76, 1.54, 11.80. III: 2.92, 1.42, 1.77, 2.74, 1,59, 10.44. IV: 3.67, 1.51, 2.87, 3.04, 1.85, 12.94. Palp: 4.15, 1.98, 3.50,–, 0.81, 10.44. Chaetotaxy: Trochanter: III, p 1; I-II-IV, 0. Femora: I-II, 0; III, d 1-1-2; IV, 0. Patellae: I- II 0; III, d 1-1-1-1, p 16, 14 on the margin (crown of thorns); IV, p 21.Tibiae: I, r 1-1-2, v 1-2-1-2-1-3; II, r 13, v 1-1-2-3; III, v 2-2-2, r 2-2, d 1, with apical crown of 14 thorns; IV, v 1-1-1-1-1-3 (spiniform). Metatarsi: I, r 1-1-1-1-1-1-2, v 2-2-2, p 1-1-2-1-1; II, r 1-1-1-2-2, v 2-1-1-1-4 (apical), p 1-1; III, p 1-1-2-1-1-2, v 1-1-1-1, r 1-1-2-1-2-3; IV, v 2-2, p 1-2-3-2-1-3, r 1-0-2-1-2. Tarsi: I, r 2-1-2-2-1-4, v 2-2-1-1-1, p 1-1-1-1; II, r 18, v 1-1-1-1- 1-1-1, p 1-1-1-1-1; III, r 1-2-1-1, p 1-1-1; IV, r 1, p 1-2-2-2-1. Total number of retrolateral spines on tibiae I, II ( Fig 1D View FIGURE 1 ): 4 and 13, respectively. Palp: tibia long, thin ( Fig 2A, B View FIGURE 2 ). Bulb ( Fig 2C–F View FIGURE 2 ) slim and slender. TA developed, PA developed. Embolus without denticles and with PS, PI, and Pac well developed. Pseudoscopula: Tarsi: I–II, sparse; III-IV, dense, uniform. Metatarsi: I-II absent, III apical and sparse, IV 1:3 apical. Trichobothria: Tibiae: I 3-3; II-II 4-3; IV 5-5. Metatarsi: I-II 8; III 6; IV 7. Tarsi: I -II 5; III 4; IV 5. Colour in alcohol: cephalic region and chelicerae reddish brown, carapace lighter. Abdomen brown; book lungs with light markings. Sternum reddish brown with a lighter center mark. Legs like cephalic region, legs III-IV with lighter tarsi–metatarsi; palp with tibia lighter. Spinnerets yellowish.

Female paratype (FML-ARAN 02274). Total length: 9.57. Carapace ( Fig 3A View FIGURE 3 ): length 4.58, width 4.44; cephalic region: length 3.20, width 4.40; clypeus small with 12 bristles; 10 bristles between PME, 4 behind each PME – PLE, 5 bristles and one larger on both sides of ocular group. Fovea: length 0.47, width 1.08. Eyes, diameters and interdistances ( Fig 3F View FIGURE 3 ): AME 0.11, ALE 0.27, PME 0.21, PLE 0.17, ocular group 0.80, anterior width 2.39, 2.09 posterior width; AME – ALE 0.73, PME – PLE 0.11, AME – PME 0.47, ALE – PLE 0.53, AME – AME 0.54, PME – PME 1.32 . Chelicerae: cheliceral apex with 9 recumbent and elongated bristles covering base of fang. Rastellum with 10 marginal, blunt spines and 5 small dorsal. Cheliceral furrow with 6 promarginal and 5 retromarginal teeth and 8 denticles in furrow, near promargin. Labium ( Fig 3B View FIGURE 3 ): length 1.13, width 0.97, with 12 anterior cuspules. Maxillae ( Fig 3B View FIGURE 3 ): anterior length 1.24, posterior length 1.67, width 1.35, with ~95/100 cuspules 1:3 ventral anterior, expanding to anterior face. Sternum ( Fig 3B View FIGURE 3 ): Center flat, length: 3.38, maximum wide 2.67, minimum width 1.63. Postlabial sigilla square, posterior ones shallow, well defined. Abdomen ( Fig 3C, E View FIGURE 3 ): length 5.02, covered by brown bristles. PMS: length 0.56; PLS with basal: medial: apical articles 0.62:0.23:0.20. Lengths of legs and palp: I: 2.76, 1.83, 1.46, 1.64, 0.91, 8.60. II: 2.79, 1.86, 1.44, 1.71, 0.85, 8.65. III: 2.67, 2.09, 1.11, 1.73, 0.78, 8.38. IV: 3.33, 1.95, 2.05, 2.04, 0.79, 10.16. Palp: 2.46, 1.66, 1.65, –, 1.81, 7.58.

Chaetotaxy: All femora: 0. Patellae: I–II, 0; III, p 4 + 9 on margin, r 7 on margin; IV, p-d 38; palp, p 1-1. Tibiae: I, v 1-1-1; II, r 30, v 1-1 spiniform setae; III, d 1, with apical crown of 15 thorns, r 12; IV, 0; palp, p 1-1-1-1-1-1, r 1-1-2-1-1. Metatarsi: I, r 7, v 1-1-2, p 14; II, r 1-2-1-1-1-1, p 1-1-1-1-2, v 1-1-2 near to the r ones; III, r 17 on row, v 2, p 10 on row; IV, p 2-1-2, d 1 anterior. Tarsi: I, r 10, v2, p 6; II, p 11, v 2, r 8; III, r 11, v-p 16; IV, v-p 24; palp, r 16, p 10, v 2 apical. Total number of retrolateral spines on tibiae I and II ( Fig 3G View FIGURE 3 ): 0 and 30, respectively. Trichobothria: Tibiae: I 3-3; II-III 3-4; IV 5-6. Metatarsi: I-II 9; III-IV 7. Tarsi: I 6; II 5; III-IV 4. Colour: cephalic region and chelicerae greenish brown, carapace lighter. Abdomen brown; book lungs with light markings. Sternum greenish brown with a lighter center mark ( Fig 3B View FIGURE 3 ), labium and maxillae darker. Legs like cephalic region. Spinnerets yellowish.

Distribution. Provinces of Santiago del Estero and Formosa ( Fig 5 View FIGURE 5 ).