Magnacrus taynguyenensis, Hoang & Yu & Wendt & West & Wirth, 2025

Magnacrus taynguyenensis gen. nov. sp. nov.

( Figs 5–8 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 , 13A, C View FIGURE 13 , 15 View FIGURE 15 , 17 View FIGURE 17 )

Type materials. Holotype ♂ ( SMNS Aran-003985), VIETNAM: Lâm Đ Ồng Province , August 2005, leg. Joe Nielsen; paratypes: 1 ♀ ( SMNS Aran-003986), 1 ♂ (VNMN-ARA-THE-00011), 1 ♀ (VNMN-ARA-THE-00012), same data as holotype; 2 ♀♀, South Vietnam, leg. Hombach, in SMF.

Etymology. The specific epithet is derived from the Tay Nguyen region, the local name for the Central Highlands of Vietnam, where the species was found.

Diagnosis. Females can be distinguished from M. tongmianensis by the following: (1) metatarsus IV of M. taynguyenensis has only a weakly developed scopula which is almost restricted in the ventral apical part and undivided ( Fig. 13A View FIGURE 13 ), whereas in M. tongmianensis , scopula on met. IV is relatively well developed, covers about distal half of the ventral surface of met. IV and divided (fig. 2H in Zhu et al. 2002 and fig. 2F in Zhu & Zhang 2008); (2) stridulatory spines on the prolateral palp coxa ( Fig. 7E View FIGURE 7 ) in M. taynguyenensis are reduced in number (10 spines), compared to M. tongmianensis (17 spines; Fig. 1E View FIGURE 1 ); (3) the long soft setae on retrolateral surface of tibia IV ( Fig. 7C View FIGURE 7 ) in the M. taynguyenensis is relatively sparse, whereas those setae are rather dense, forming a brush-like structure in the M. tongmianensis ( Fig. 1C View FIGURE 1 ); (4) the notch in the middle of the undivided spermatheca ( Fig. 7D View FIGURE 7 ) in the M. taynguyenensis is relatively deeper than those in the M. tongmianensis ( Fig. 1D View FIGURE 1 ). In males, M. taynguyenensis can be distinguished from M. tongmianensis by the following: (1) M. taynguyenensis has five main keels (PS, PA, PI, SA, A) on the palpal bulb, without distinct VTM ( Fig. 6A–F View FIGURE 6 ), whereas in M. tongmianensis with 7 keels (PS, PA, PSA, PI, RB, A, SA) and a distinct VTM are presented ( Fig. 3A–F View FIGURE 3 ); (2) M. taynguyenensis is spineless on the ventral apical part of tibia I ( Fig. 5D View FIGURE 5 ), different to M. tongmianensis , which has two spines there ( Fig. 2D View FIGURE 2 ); (3) ERF in M. taynguyenensis is clearly above 40 ( Fig. 6F View FIGURE 6 ), significantly higher than the ERF in M. tongmianensis (ERF is ca. 33) ( Fig. 3F View FIGURE 3 ).

Description of Male holotype, SMNS Aran-003985, with body length: 34.46 (including chelicerae).

Color (in life) ( Fig. 8B View FIGURE 8 ): Femora of the legs and palps black, the rest of the legs and palps are gray on the upper side. Joint ring between tibia and metatarsus distinct and whitish, carapace, opisthosoma and cheliceral bases bronze-colored.

Carapace ( Fig. 5A View FIGURE 5 ): length 14.16, width 11.45. Fovea: 1.58 wide, 1.66 curved length, procurved.

Chelicerae ( Fig. 5F View FIGURE 5 ): length 7.5, width 5.0. Retrolaterally with a large field of plumose setae, baso-dorsally with a smaller field of long strong plumose setae, baso-ventrally with 5 long, sword-shaped plumose setae.

Clypeus: width 0.39, smaller than width of OT.

Eyes: OT length 1.81, width 2.46. Diameter (longitudinal) ALE: 0.64; AME: 0.59; PLE: 0.48, PME: 0.38; inter-distances: ALE–AME: 0.24; AME–AME: 0.26; PLE–PME: 0.07.

Maxillae ( Fig. 5E View FIGURE 5 ): length (incl. trochanter) 7.5. Prolaterally plano-convex, anterior prolateral lobe well pronounced. Retrolateral face mostly glabrous. Prolateral face with 10 short thorn-like black spines and 3 short thorn-like black setae pointing forward and increasing in length and size from posterior to anterior, in two rows, fine plumose setae above suture, dorso-anterior edge with a row of 6 elongated black spiniform setae.

Labium: length 1.82, width 2.36. 106 cuspules in anterior area of labium.

Sternum ( Fig. 5B View FIGURE 5 ): length 6.95, width 3.67. Narrow, wider posteriorly than anteriorly, with a thin intermix of short setae and sparse longer setae, more so along edges. No spines on edges, but thicker setae along opposing edges of coxa IV. Sternal sigilla: three pairs (not including labio-sternal sigilla), glabrous, PSS largest, ovoid, length 0.51, 0.25 from sternum edge, 2.08 between PSS and clearly visible. Middle and anterior pair obscured by setae, middle pair smaller than PSS and anterior pair smaller than middle pair. Labiosternal groove: glabrous, slightly narrower medially, groove with low oblong cuticular mound on either side of medial narrowing.

Leg setation: all legs uniformly covered with short pile setae with scattered longer guard setae, unlike male M. tongmianensis .

Legs: formula IV, I, II, III. LRF~ 97. Leg lengths (fem., pat., tib., met., tar., total): I 12.0, 6.5, 11.0, 9.0, 7.0, 45.5; II 10.0, 6.0, 8.0, 7.5.0, 6.0, 37.5; III 9.5, 5.0, 6.0, 7.0, 5.0, 32.5; IV 13.0, 5.0, 12.0, 11.0, 6.0, 47. Tar. IV uniform without transverse pallid medial suture. Tibia apophysis on leg I ventral with a single prolateral apophysis with numerous spines at its tip ( Fig. 5C–D View FIGURE 5 ).

Scopula: met. and tar. I–IV, undivided. Met. I: 73%; II: 66%; III: 51%; IV: 25%, all divided by strong setae.

Coxae: coxae I–IV. Ventral measurements for coxa + trochanter: length: I–10; II–9; III–7; IV–7.

Spines: Leg: I Met. 1 v, a, m; 1 v, a, rl; II Tib. 1 v, a, rl; Met. 1 v, a, rl; 1 v, a, m; 1 v, a, pl; III Tib. 1 d, a, pl; 1 d, a, rl; Met. 1 d, a, rl, 1 v, a, pl; 1 v, a, m; 1 v, a, rl; IV Tib. 1 v, a, pl; 1 v, a, rl; Met. 1 d, a, rl; 1 v, a, pl; 1 v, a, m; 1 v, a, rl.

Claws: all unarmed, no third claw on leg IV.

Abdomen: length 12.8, wide: 9.21.

Palpal bulb ( Fig. 6A–F View FIGURE 6 ): Embolus with four keels, PS, PA, PI, SA and A keel, tegulum ventrally basal without a bulge-like process (VTM), ERF~ 42.

Spinnerets: deformed, not measurable.

Description of Female paratype (SMNS Aran-003986), with body length: 52 (including chelicerae).

Color (in life) ( Fig. 8A View FIGURE 8 ): Femora of the legs and palps black, the rest of the forelegs, cheliceral bases and palps light brown, the rear legs dark brown, carapace dark gray to black, opisthosoma dark gray. The rear legs have long dense brown setae, especially on retrolateral side from patella to tarsus. Femur I has a retroventral fringe of short dense red setae.

Carapace ( Fig. 7A View FIGURE 7 ): length 21, width 17. Fovea: 4.96 wide, 5.17 curved length, recurved (Note: This may be a variation that is only present in this specimen, as the fovea is usually procurve, as is the case in the male M. taynguyenensis ).

Chelicerae ( Fig. 7F View FIGURE 7 ): length 12, width 5. Retrolaterally with a large field of plumose setae, baso-dorsally with a smaller field of strong plumose setae, baso-ventrally with 5 long, sword-shaped plumose setae.

Clypeus: width 1.79, clearly smaller than width of OT.

Eyes: OT length 4.47, width 5.96. Diameter (longitudinal) ALE: 1.45; AME: 1.41; PLE: 1.11, PME: 1.05; inter-distances: ALE–AME: 0.82; AME–AME: 0.63; PLE–PME: 0.27.

Maxillae ( Fig. 7E View FIGURE 7 ): length (incl. trochanter) 13.21. Prolaterally plano-convex, anterior prolateral lobe well pronounced. Retrolateral face mostly glabrous. Prolateral face with 6 short thorn-like black spines and 4 long thorn-like black setae pointing forward and increasing in length and size from posterior to anterior, in two rows, fine plumose setae above suture, dorso-anterior edge with a row of 9 elongated black spiniform setae.

Labium: length 2.46, width 4.12. 77 cuspules in anterior area of labium.

Sternum ( Fig. 7B View FIGURE 7 ): length 10.38, width 6.94. Wider posteriorly than anteriorly, with a thin intermix of short setae and sparse longer setae, more so along edges. No spines on edges, but thicker setae along opposing edges of coxa IV. Sternal sigilla: three pairs (not including labio-sternal sigilla), glabrous, PSS largest, ovoid, length 0.86, 0.74 from sternum edge, 3.27 between PSS and clearly visible. Middle and anterior pair obscured by setae, middle pair smaller than PSS and anterior pair smaller than middle pair. Labiosternal groove: glabrous, slightly narrower medially, groove with low oblong cuticular mound on either side of medial narrowing.

Leg setation: all legs covered with short pile setae with scattered longer guard setae ( Figs 7C View FIGURE 7 , 8A View FIGURE 8 ). Leg III & IV patella, tibia and metatarsus with abundant dorso- and retrolateral guard setae not as dense as found on female M. tongmianensis .

Legs: formula IV, I, II, III. LRF~ 86. Leg lengths (fem., pat., tib., met., tar., total): palp 8.0, 7.0, 7.2, –, 7.0, 29.2; I 14.0, 9.0, 11.0, 7.5, 7.0, 48; II 12.5, 8.0, 8.5, 7.0, 6.0, 42; III 11.5, 7.5, 7.5, 8.0, 5.0, 39.5; IV 15.0, 8.5, 13.0, 13.0, 7.0, 56. Tar. IV uniform without transverse pallid medial suture.

Scopula: met. and tar. I–IV, undivided. Met. I: 82%; II: 75%; III: 56%; IV: <5%.

Coxae: coxae I–IV. Ventral measurements for coxa + trochanter: length I–14; II–11; III–11; IV–12.5.

Spines: Palp Met.: 1 v, a, rl; 1 v, a, pl; Leg: I Met.: 1 v, a, rl; 1 v, a, m; II Tib.: 1 v, a, rl; Met.: 1 v, a, rl; 1 v, a, m; 1 v, a, pl; III Tib.: 1 v, a, rl; 1 v, a, pl; Met.: 1 v, a, pl; 1 v, a, m; 1 v, a, rl; IV Tib.: 1 v, a, rl; Met.: 1 d, a, rl; 1 v, sm, rl; 1 v, a, rl; 1 v, a, m; 1 v, a, pl.

Claws: all unarmed, no third claw on leg IV.

Abdomen: length 20, wide: 20.

Genitalia ( Fig. 7D View FIGURE 7 ): Spermatheca undivided consisting of two lobes connected by a deep dent in the middle. Width 5.29, height at the highest point of the left lobe 1.06, of the right lobe 1.16, at the lowest point in the middle 0.36. The angle between the two lobes is 98.35°.

Spinnerets: PMS: deformed, not measurable; PLS: length 7.74.

Distribution. Vietnam (Lâm Đồng) ( Fig. 17 View FIGURE 17 ).

Natural history. Type specimens of M. taynguyenensis gen. nov. sp. nov. were collected from relatively high elevations (above 1000 m elev.). The general habitat consists of pine forests with an understory of vegetation consisting of grasses and low bushes ( Fig. 15A View FIGURE 15 ). The self-excavated fossorial retreats of M. taynguyenensis were found on gently sloped ground amongst shaded vegetation in clay-like soil on roadside embankments at an elevation of 1400–1600 meters ( Fig. 15A View FIGURE 15 ). Retreats of adult females averaged 5 cm in diameter and 30–40 cm in length and ran downward under the ground surface, unbranched, in an ‘L’ shape, ending in a blind chamber. The interior length of the burrow was lightly lined with silk. Like M. tongmianensis burrows, M. taynguyenensis incorporates surrounding organic debris, such as grasses and pine needles, with silk to form a trumpet-shaped entrance for the burrow ( Fig. 15B View FIGURE 15 ). Occupied burrows are usually silken over by day, possibly to prevent predacious ants and wasps from entering. When extracted from the retreat, M. taynguyenensis will become very defensive and readily bite if further provoked. Nothing is known about the life cycle of M. taynguyenensis . Males have been reported wandering in November and it is suspected this is the breeding season for this species in the Central Highlands of Vietnam (Nielsen, pers. obs.).