Odontolabis taynguyensis Xin, Zhong & Qi, 2025

Xin, Fei-Yi, Zhong, Xiao-Tian, Li, Chai, Li, Xin-Quan, Qi, Zhi-Hao & Wu, Hui, 2025, Integrative COI and morphological analyses: Revision of the Odontolabis platynota (Hope, 1845) species complex (Coleoptera: Lucanidae) with description of a new species from Vietnam, Zootaxa 5673 (1), pp. 79-94 : 81-86

Odontolabis taynguyensis Xin, Zhong & Qi , sp. nov.

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( Figs. 1 ; 2 ; 4A–E ; 5A–B, E–F ; 6A–B, E–F ; 7A–D ; 8A–C ; 9A ; 10A–F).

Type locality. Vietnam, Dak Nong, Dak Song.

Type material. Holotype: telodont male ( NACRC: IOZ (E) 224772): VIETNAM, Dak Nong, Dak Song , alt. 800 m, VI.2024, local collector leg . Paratypes ( 16 males, 7 females): 1 mesodont male ( CCZB): VIETNAM, Lam Dong, Da Lat, alt. 1000–1200 m, VI.2019, Van Ngoc Dang leg. ; 1 telodont male ( CFYX), 1 telodont male ( CXTZ): same data as holotype .; 2 females ( CCZB), 1 female ( CCZB; IMS: X2 ), 1 female ( CZHQ): VIETNAM, Lam Dong, Bao Loc , alt. 1000–1200 m, V.2019, Van Ngoc Dang leg. ; 1 female ( CCZB): VIETNAM, Lam Dong, Bao Loc , VI.2023, alt. 1000–1200 m, Van Ngoc Dang leg. ; 1 telodont male, 1 female ( CCZB): VIETNAM, Lam Dong, Bao Lam , VIII.2018, alt. 1000–1200 m, Van Ngoc Dang leg. ; 1 female ( CCZB): VIETNAM, Lam Dong, Bao Lam, Dambri , alt. 1000–1200 m, VIII.2018, Van Ngoc Dang leg. ; 1 telodont male, 1 mesodont male, 1 amphiodont male ( CCZB): VIETNAM, Lam Dong, Bao Lam, Dambri , alt. 1000–1200 m, VIII.2018, Van Ngoc Dang leg. ; 1 priodont male ( CCZB): VIETNAM, Lam Dong, Bao Lam, Dambri , alt. 1000–1200 m, IV.2023, Van Ngoc Dang leg. ; 2 mesodont males ( CCZB): VIETNAM, Kon Tum, Dak Long , alt. 1000–1200 m, VI.2023, Van Ngoc Dang leg. ; 1 telodont male ( CFYX): VIETNAM, Dak Lak, alt. 1000–1200 m, V.2018, local collector leg .; 1 mesodont male ( CCZB): VIETNAM, Dak Lak, alt. 1000–1200 m, IV.2018, local collector leg .; 1 amphiodont male ( CZHQ): VIETNAM, Lam Dong, Bao Lam, Dambri , alt. 1000–1200 m, VIII.2019, Van Ngoc Dang leg ; 2 telodont males, 1 mesodont male ( CXTZ): VIETNAM, Kon Tum, alt. 800–1200 m, VI.2025, local collector leg .

Differential diagnosis. The new species is closely to Odontolabis platynota ( Hope, 1845) morphologically, but the following characters will help to recognize. Male: (1) the new species exhibits a larger body size within the same male mandibular morphotypes ( Figs. 1–3 ); (2) a shallower and wider emargination of the apical margin of the head ( Fig. 4 ); (3) mandible more slender, with the tiny or absent basal mandibular protrusion in telodont males of new species ( Fig. 4 ); (4) the new species mainly exhibits acutely angled cephalic lateral projections, though a minor subset of individuals demonstrates a blunter morphology ( Fig. 4 ). Female: (1) the larger body size is also being within female ( Fig. 5 ); (2) the protibia exhibits a straighter outer margin, with fewer and sparsely distributed spines ( Figs. 6A–D ); (3) the head exhibits more numerous and coarser punctures ( Figs. 6E–H ).

Description of the holotype, telodont male ( Fig. 1A, D ). Body length 42.6 mm. Length of particular body parts: head ( 6.7 mm), mandible ( 12.5 mm), pronotum ( 6.9 mm), elytra ( 18.1 mm); width: head (13.0 mm), pronotum ( 14.9 mm), elytra ( 14.4 mm).

Habitus ( Fig. 1A, D ). Body black, faintly glossy; body without pubescence except for apical and basal margin of pronotum and legs, apex of protibia mesotibia and metatibia with yellow setae.

Head ( Fig. 4A ) transverse with dense punctures on both anterolateral sides. Apical margin widely concave on the middle. Both postocular lateral margins noticeably protruding outward. Canthus long and wide, completely surround the eye. Clypeolabrum tiny and subtriangle, visible in dorsal view, produced anteriorly. Mandible about 1.9 times longer than head, inner margin smooth from base to teeth; in lateral view, almost horizontal; in dorsal view, obviously curved, width nearly uniform, with 3 continuous subtriangle inner teeth apically.Antennal club with 3 antennomeres; antennomeres 8–9 subquadrilateral; antennomere 10 semi-elliptic.

Pronotum transverse, 2.2 times wider than long, wider than head, widest between two lateral angles. Anterior margin bisinuate, posterior margin slightly bisinuate. Anterior angles rounded and directed forwards, lateral angles sharp and posterior angles blunt.

Scutellum subtriangular, nearly smooth with sparse punctures, width almost as long as length.

Legs. Protibia with 3–5 conspicuous sharp protuberances (excluding apical fork) along outer margin, apex bifurcate with branches moderately sharp at tip. Mesotibia and metatibia straight and smooth at outer margin with a terminal spine.

Elytra elongate, 1.3 times longer than wide, anterior margin significantly narrower than pronotum.

Abdomen and aedeagus. Abdominal ventrite VIII ( Fig. 7A ) with 2 slightly protruding tips on basal margin near middle. Abdominal tergite VIII ( Fig. 7B ) nearly semilune, lateral angles absent. Ventral plate of abdominal segment IX ( Fig. 7D ) elongate without membranous stripe, basal part extremely narrow, then suddenly became wider, widens gradually to apex and constricted near apex. Aedeagus ( Fig. 8A–C ) in dorsal view about 3.4 times longer than wide. Basal piece elongated, weakly longer than parameres in dorsal view, with a significant and relatively broad pair of sclerotized dorsal plates, and almost as wide as paramere; ventral plate at apical end of basal piece membranous. Paramere relatively narrow, with a small inner curvature at base, apex of paramere curved outward. Penis about 0.7 times length of paramere in ventral view. Flagellum ( Fig. 9A ) long, about 2.6 times longer than aedeagus, apex of flagellum simple.

Variation of males (n=16). In general, body length typically follows the order of telodont males> mesodont males> amphiodont males> priodont males (30.0–47.0 mm) ( Figs. 1B, E ; 2 ), while the mandible-to-head length ratio consistently exhibits the same hierarchical pattern (telodont males> mesodont males> amphiodont males> priodont males) ( Figs. 4A–E ); conversely, the depth of the cephalic apical emargination displays an inverse sequence, with telodont males <mesodont males <amphiodont males <priodont males ( Figs. 4A–E ). In addition, the mandible of larger telodont males less pronounced mandibular curvature apically ( Fig. 1B ). A few telodont males exhibit a tiny basal mandibular protrusion ( Fig. 1C , 4B ). Mandible of mesodont males straighter, with a large basal mandibular protrusion, apical teeth longer ( Fig. 4C ). Mandible of amphiodont males with almost continuous teeth at inner margin or smooth part shorter ( Fig. 4D ). Basal mandibular protrusion of priodont males weakened into teeth, show a row of continuous teeth at inner margin ( Fig. 4E ).

Female paratypes (n=7). Body length 25.6–30.1 mm.

Habitus ( Figs. 5A–B, E–F ). Body black, faintly glossy and smooth; body without pubescence.

Head ( Figs. 6E–F ) covered with punctures near eye. Canthus triangular, with blunt lateral angle. Clypeolabrum tiny, transverse. Mandibles asymmetric, about 0.7 times length of head, with hackly inner margin. Antennal club with 3 antennomeres; antennomeres 8–9 subquadrilateral; antennomere 10 semi-elliptic.

Pronotum transverse, 2.2 times wider than long, widest across lateral angles; anterior margin bisinuate, posterior margin slightly bisinuate; anterior angles rounded; lateral angles clearly defined; posterior angles sharp.

Scutellum relatively smooth, about 2 times wider than long.

Elytra about 1.2 times as long as wide. Surface relatively smooth, with shallow punctures.

Legs ( Figs. 6A–B ). Protibia with sparse 3 conspicuous sharp protuberances (excluding apical fork) along outer margin, apex bifurcate with branches moderately sharp at tip, extend apically. Mesotibia and metatibia straight and smooth at outer margin with a terminal spine.

Abdomen and genitalia.Abdominal ventrite VIII (Figs. 10A,D) with membranous area at central part;Abdominal tergite VIII (Figs. 10E, H) semicircular, with triangular membranous area at central part basally. Hemisternite (Figs. 10C, F) with slightly curved oblique at lateral margins, apical margin rounded with setae. Spermathecal duct relatively short. Spermatheca appears symmetrically paired, exhibiting a bulbous morphology positioned terminally on the spermathecal duct. Spermathecal gland absent.

Etymology. Species name taynguyensis is derived from “Tây Nguyên” (Vietnamese: Central Highlands), the name of western plateau region in Vietnam.

Distribution. Vietnam ( Dak Nong, Lam Dong, Kon Tum, Dak Lak).

DNA barcode. A partial sequence of the mitochondrial gene of cytochrome oxidase subunit I ( COI) of the holotype was uploaded to GenBank with accession number PV351613, and a female paratype (X2) from Lam Dong: PV849456.

Phylogenetic analysis based on COI fragment. The “TIM2+F+I+G4” models with the lowest BIC scores were selected as the optimal substitution pattern descriptors. Phylogenetic analyses revealed a distinct separation of the new species from Odontolabis platynota ( Hope, 1845) , with strong nodal support in the ML tree ( Fig. 11 ). Genetic divergence analyses ( Table 1) within the genus Odontolabis demonstrated clear hierarchical structuring. Intraspecific genetic distances (K2P model) ranged from 0.00149 to 0.03120, while interspecific divergence across the genus averaged 0.14. Crucially, the genetic distance between the newly proposed species and O. platynota spanned 0.06601 –0.07779. This value far exceeds the upper limit of intraspecific variation (0.03120) and approaches half of the genus-wide interspecific average (0.14), demonstrating a clear-cut species-level divergence. Combined with morphological distinctiveness and phylogenetic separation, these data unequivocally validate the new species as an independent taxonomic entity.

Figures

FIGURE 1. Male habitus of Odontolabis taynguyensis Xin, Zhong & Qi, sp. nov.. A, D, holotype, Dak Nong, Vietnam, 42.6 mm, telodont form; B, E, paratype, Dak Nong, Vietnam, 46.8 mm, telodont form; C, F, paratype, Lam Dong, Vietnam, 47.0 mm, telodont form with tiny basal mandibular protrusion. A–C dorsal view; D–F, ventral view. Scale bar = 10.0 mm.

FIGURE 2. Habitus of male paratypes of Odontolabis taynguyensis Xin, Zhong & Qi, sp. nov.. A, D, Dak Lak, Vietnam, 36.0 mm, mesodont form. B, E, Lam Dong, Vietnam, 33.2 mm, amphiodont form. C, F, Lam Dong, Vietnam, 33.2 mm, priodont form. A–C, dorsal view; D–F, ventral view. Scale bar = 10.0 mm.

FIGURE 3. Male habitus of Odontolabis platynota (Hope, 1845). A, E, Ha Giang, Vietnam, 41,2 mm, telodont form; B, F, Fujian, China, 38.5 mm, mesodont form; C, G, Zhejiang, China, 29.0 mm, amphiodont form; D, H, Guangxi, China, 26.2 mm, priodont form. A–D, dorsal view; E–H, ventral view. Scale bar = 10.0 mm.

FIGURE 4. Male head of Odontolabis species in dorsal view. A–E, O. taynguyensis Xin, Zhong & Qi, sp. nov.; A, holotype, Dak Nong, Vietnam, telodont form; B, paratype, Lam Dong, Vietnam, telodont form with tiny basal mandibular protrusion; C, paratype, Dak Lak, Vietnam, mesodont form; D, paratype, Lam Dong, Vietnam; amphiodont form; E, paratype, Lam Dong, Vietnam, priodont form. F–I, O. platynota (Hope, 1845); F, Ha Giang, Vietnam, telodont form; G, Fujian, China, mesodont form; H, Zhejiang, China, amphiodont form; I, Guangxi, China, priodont form.

FIGURE 5. Female habitus of Odontolabis species. A–B, E–F, O. taynguyensis Xin, Zhong & Qi, sp. nov.; C–D, G–H, O. platynota (Hope, 1845). A, E, Lam Dong, Vietnam, 30.1 mm; B, F, Lam Dong, Vietnam, 29.0 mm. C, G, Nghe An, Vietnam, 25.6 mm; D, H, Guangxi, China, 24.1 mm. A–D, dorsal view; E–H, ventral view. Scale bar = 10.0 mm.

FIGURE 6. Female protibia (A–D) and head (E–H) of Odontolabis species. A–B, E–F, O. taynguyensis Xin, Zhong & Qi, sp. nov.; C–D, G–H, O. platynota (Hope, 1845). A–B, E–F, Lam Dong, Vietnam. C, G, Nghe An, Vietnam; D, H, Guangxi, China.

FIGURE 7. Male abdominal ventrite VIII (A, E, I), abdominal tergite VIII (B, F, J) and abdominal segment IX (C–D, G–H, K–L) of Odontolabis species. A–D, O. taynguyensis Xin, Zhong & Qi, sp. nov., holotype; E–L, O. platynota (Hope, 1845), E–H, Ha Giang, Vietnam, telodont form; I–L, Fujian, China, mesodont form. B, C, F, G, J, K, dorsal view; A, D, E, H, I, L, ventral view. Scale bar = 1.0 mm.

FIGURE 8. Aedeagus (excluding flagellum) of Odontolabis species.A–C, O. taynguyensis Xin, Zhong & Qi, sp. nov., holotype; D–I, O. platynota (Hope, 1845), D–F, Ha Giang, Vietnam, telodont form; G–I, Fujian, China, mesodont form. A, D, G, dorsal view; C, F, I, ventral view; B, E, H, lateral view. Scale bar = 1.0 mm.

FIGURE 9. Aedeagus of Odontolabis species in ventral view. A, O. taynguyensis Xin, Zhong & Qi, sp. nov., holotype; B–C, O. platynota (Hope, 1845), B, Ha Giang, Vietnam, telodont form; C, Fujian, China, mesodont form. Scale bar = 1.0 mm.

FIGURE 11. Maximum-likelihood phylogenetic tree based on COI fragments between stag beetles of Odontolabis. SH-aLRT support (%) / ultrafast bootstrap support (%) are labeled near the branch. The purple part denote the outgroup, the red part denotes the new species, and the blue part denote O. platynota (Hope, 1845) from different geographic localities.