taxonID	type	description	language	source
03E12827E97FFFCCD0B276F9FDA8F9AD.taxon	vernacular_names	Chinese common name: Ê ẑDāē	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E97FFFCAD0B2754DFB50FBD9.taxon	vernacular_names	Chinese common name: ÎŝÊ ẑDā	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E97FFFCAD0B2754DFB50FBD9.taxon	description	(Figs. 1 A – C, 3 A – B, 4 A – D, 5 A – F, 7 C – F)	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E97FFFCAD0B2754DFB50FBD9.taxon	materials_examined	Type material examined. Prismognathus formosanus: neotype (Figs. 1 A – E), male, by present designation (ASIZHX): “ TAIWAN: Nantou Co. | Yushan Tataka, 2600 m | V. 1982, local collector ” || “ NEOTYPE | Prismognathus formosanus Nagel, 1928 | des. J. - Z. Lin 2024 ”. Prismognathus piluensis: none. The holotype (male, Fig. 3 A) of this species was originally deposited in NMNS, but currently it was not located in the collection by the author. Additional material examined. TAIWAN: Nantou County: 2 ♂♂, 1 ♀, Yushan Tataka, 2610 m, V. 1982; 3 ♂♂, Meifeng, 2110 m, V. 2018 (reared). Hualien County: 7 ♂♂, 2 ♀♀, Pilu-Guanyuan, 2100 − 2370 m, IX. 1984. Chiayi County: 13 ♂♂, Alishan, 2300 m, VIII. 2019 (reared). Taichung City: 12 ♂♂, 3 ♀♀, Daxueshan, 2150 m, 22. IX. 2009. Hsinchu County: 7 ♂♂, 3 ♀♀, Guanwu, 1920 m, 08. IX. 2018. Taitung County: 2 ♂♂, Xiangyang, 2320 m, IX. 2016 (reared). Yilan County: 4 ♂♂, Datong, 1950 m, 28. VIII. 2021. All specimens are deposited in JZLC.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E97FFFCAD0B2754DFB50FBD9.taxon	description	Description of the neotype, male (Figs. 1 A – C, 4 A – D). Measurements. Body length 21.5 mm (Fig. 1 A). Original length of the holotype derived from primary description was 22.5 mm (Fig. 3 B). Body 2.7 times as long as wide, widest around the anterior one-third of the pronotum. The specific dimensions are as follows: head length 3.9 mm and width 5.6 mm (W / L 1.44); mandible length 3.6 mm (approximately 0.9 times the head length); pronotum length 4.5 mm and width 7.8 mm (W / L 1.73); and elytra length 11.0 mm and width 7.0 mm (L / W 1.57). Appearance and integument. The body is entirely reddish-brown to castaneous (Figs. 1 A – C). The surface is moderately lustrous, exhibits a metallic sheen, and is glabrous. Head is approximately 1.4 times as broad as long, widest across the eyes. The vertex is gradually depressed in a triangular area bordered by the anterolateral angles and the posterior margin. The frontal margin is distinctly and roundly emarginate in the medial part. The anterolateral angles protrude. The preocular margin is substraight, the angle is slightly obtuse, and the postocular margin is slightly arcuate. The canthus does not exceed the outer margin of the eye. The clypeolabrum is small and tuberculate. The head surface is covered with well-developed, fine punctation. Mandible is about 0.9 times as long as the head. The outer margin is essentially straight, moderately incurved near the distal third of the apex. The apex is bifurcated, featuring a dorsal tooth. Dentition: The ventral surface features 2 – 3 median teeth, continuously extending from the apex toward the base, with a gap between these median teeth and the double subbasal teeth (add some references for figures). The dorsal ridge possesses a subbasal tooth at the basal third. Antennae are geniculate. The antennal club is composed of three pubescent antennomeres; antennomeres 8 – 10 are lamellate; antennomere 10 has the medial extension at the apex arcuate and enlarged. Ventral head structures include the mentum, which is subtrapezoidal, micropunctate, with anterolateral angles rounded. The submentum is inverted trapezoidal and micropunctate. The gula is elongate and smooth. Pronotum is 1.7 times as wide as long, widest at the lateral angles, and about 1.4 times as wide as the head. Punctation is coarse and deeply impressed, and the surface features approximately four impunctate circular foveae. The lateral margin is smooth, weakly curved before the lateral angle and distinctly concave after. The posterior margin is bisinuate. The lateral angles are located at the posterior twofifths and are acute. The posterior angles are widely rounded. Scutellar shield is linguiform (tongue-shaped). The surface is finely punctate, attenuating posteriorly. Elytra are 1.5 times as long as wide, widest around the posterior one-third, and 0.8 times as wide as the pronotum. The surface is micropunctate and smooth, lacking striations or large punctures. Legs All legs are dark reddish-brown. The protibia has its outer margin equipped with 4 – 5 large teeth; the apex is forked with sharp branches. The mesotibia features one lateral spine and one denticle. Metatibia features one inconspicuous lateral denticle. Male genitalia features several characteristics in the abdominal segments: Abdominal tergite VIII is subhexagonal, only slightly membranous along the midline anteriorly; sternite VIII is rather transverse, without a membranous area. Abdominal tergite IX is widely emarginate at the anterior margin; pleurite IX is dorsally approaching; sternite IX has only a small membranous area in the middle of the posterior part (Figs. 4 C – D). Aedeagus has the paramere length approximately 2 / 3 to 3 / 4 of the basal piece, lacking a basal process, and with the apex distinctly upturned and rounded. The basal piece is distinctly constricted in the anterior part, featuring a pair of sclerotized dorsal plates. The ventral caudal plate is deeply and broadly excavated centrally, with the bottom of the split posterior to the ventral margin of the basal piece. The median lobe is about 4 / 5 of the paramere length, with bilateral branches subtriangular in the apical part, and the apical margin slightly curved. The flagellum is short, approximately as long as the aedeagus, belt-like in the basal 4 / 5, becoming thread-like in the distal fifth but slightly enlarged at the apex (Figs. 4 A – B). Variation. Body length (including mandibles): Males: 18.0 – 31.5 mm; females: 16.5 – 23.0 mm. Variation is primarily manifested in color polymorphism and the morphology of the male mandibular dentition. The body color exhibits considerable plasticity; while most individuals from the type locality are reddish-brown, populations from the northern and eastern regions show a broader spectrum of hues, including dark coffee, brown, reddish-brown, and brownish-tea shades. This study regards the observed color variation as random and unstable, lacking clear geographical significance for taxonomic delineation. The variation in mandibular dentition follows a geographical cline: specimens from the southwestern populations possess sparser, fewer denticles with large interspaces; conversely, populations from the northern, central, and eastern regions exhibit more numerous, denser denticles with smaller interspaces. Crucially, these morphological differences are gradual and continuous. Intermediate forms are frequently observed in transitional zones such as Taichung and Nantou. Due to this high degree of continuity, this study cannot effectively separate the two observed phenotypes, rendering these features unsuitable for diagnostic purposes. Furthermore, the male mandibles exhibit allometric growth: larger males develop a prominent, dorsally erect, and anteriorly inclined projection, often bifurcated (furcated) at the apex, the size and distinction of which increase with overall body size.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E97FFFCAD0B2754DFB50FBD9.taxon	distribution	Distribution. Taiwan (Hsinchu, Miaoli, Taichung, Nantou: Yushan, Chiayi, Kaohsiung, Pingtung, Taitung, Hualien, Yilan), all specimens recorded from the elevation between 1800 − 2800 m.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E97FFFCAD0B2754DFB50FBD9.taxon	discussion	Taxonomic notes. The original holotype for P. formosanus was destroyed. This created a problem for nomenclatural stability. The author addressed this by formally designating a neotype for P. formosanus. This action fulfills a primary ICZN (1999) requirement. The designation officially fixes the application of the name. Finding the P. piluensis type material proved to be complicated. The original article stated the types should be at the National Museum of Nature and Science Tokyo (NMNS). However, the author personally checked the collection. Research confirmed the type series is non-existent there. The original author of the taxon already passed away. Contact with any possible relatives was unsuccessful (S. Nomura 2022, personal communication). This justified using other comprehensive material for the subsequent analysis. The author conducted a comprehensive examination of available specimens from several Taiwanese localities, including topotypical material from Pilu. The morphological traits previously cited for separating P. piluensis proved unstable. These features display a continuous gradient or clinal variation across populations. Crucially, populations in intermediate spots like Alishan exhibit both purported genital morphotypes (Huang & Chen 2017). Furthermore, the author’s examination of additional specimens from Daxueshan, Guanwu, and Meifeng revealed numerous intermediate individuals that combine the alleged diagnostic traits. This extensive variation makes a clear morphological diagnosis impossible. Concurrently, the females are morphologically identical across the entire geographical range. Overall, this analysis provides substantial evidence to conclude that P. piluensis is simply an intraspecific variation within P. formosanus. Molecular data also supports this conclusion. Tsai & Yeh (2016) found that molecular separation of the two is unsupported. The study compared the original description and figures against multiple topotypical specimens. The findings fit entirely within variation of P. formosanus. Considering all these integrated lines of evidence, the name P. piluensis is formally treated here as a junior synonym of P. formosanus. Overall, proposing two synonymies and establishing nomenclatural stability greatly streamlines the overall classification. The author acknowledges that minor morphological differences persist among populations from geographical extremes (e. g., Yushan and Pilu). However, these slight deviations are interpreted as intraspecific variation within geographical morphotypes, rather than supporting species or subspecies rank. This assessment precisely echoes the divergence hypothesis proposed by Huang & Chen (2017), which suggested that these two populations may still be in the process of divergence. For future work, systematic and intensive sampling targeting the transitional zones between different morphological clusters is essential. Mapping the precise boundaries of this morphological, and potential molecular genetics, differentiation will be key. This mapping is crucial for grasping the specific roles altitude and geographical isolation play in shaping the species’ variation patterns.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E979FFC7D0B277BDFB78FE09.taxon	vernacular_names	Chinese common name: aeÊ ẑDāÎŝ 亞ª	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E979FFC7D0B277BDFB78FE09.taxon	description	(Figs. 2 A – B, 6 A – F, 7 A – B)	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E979FFC7D0B277BDFB78FE09.taxon	materials_examined	Type material examined. Prismognathus davidis cheni: holotype (Fig. 2 A), male (NHM): “ TAIWAN | Li-Shan, X 1972 | Chen leg. ”. Examined from high-resolution photographs only. Prismognathus davidis nigerrimus: holotype (Fig. 2 B), male (MSNT): “ TAIWAN, Hualien-Hsien | Pilu | 12. IX. 1992 | C. K Yu leg. ” Additional material examined. TAIWAN: 8 ♂♂ 2 ♀♀, Taichong, Li-Shan, 2000 m 06. IX. 2010, local collector leg.; 2 ♂♂, Nantou, Shanlinsi, 1600 m 11. IX 2022, local collector leg.; 4 ♂♂ 1 ♀, Hsinchu Guanwu, 1920 m 08. IX. 2020, local collector leg.; 3 ♂♂, New Taipei City Taman, 1920 m 18. IX. 2016, local collector leg.; 4 ♂♂, Yilan Siyuan Pass, 1948 m 03. IX. 2015, local collector leg. All specimens are deposited in JZLC.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E979FFC7D0B277BDFB78FE09.taxon	description	Variation. Body length (including mandibles): Male: 16.0 – 36.0 mm, female: 14.5 – 24.0 mm. The subspecies shows marked color polymorphism, with individuals varying from blackish-brown to bright reddish-brown, often co-occurring within the same population. The color change follows a clear geographical clinal trend, resulting in boundaries between different color forms that appear continuous and transitional: individuals from the northern and eastern populations are typically dark black; those from the central regions (e. g., Lishan in Taichung, Nantou) are predominantly dark brown, yet simultaneously display both black and reddish-brown morphs, indicating a transitional zone; moving south of Nantou, through Chiayi, Kaohsiung, and Pingtung, the body color mainly shifts to reddish-brown. Furthermore, the male mandibular morphology is influenced by body size (allometry): in smaller individuals, the upper mandibular projection is relatively weak with less distinct upward curvature; as the body size increases, the projection becomes more developed, and the upward curvature of the mandibles significantly increases.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E979FFC7D0B277BDFB78FE09.taxon	distribution	Distribution. Taiwan (New Taipei City, Taoyuan, Hsinchu, Miaoli, Taichung: Li-Shan, Nantou, Chiayi, Kaohsiung, Pingtung, Taitung, Hualien, Yilan), all specimens recorded from the elevation between 1600 − 2500 m.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
03E12827E979FFC7D0B277BDFB78FE09.taxon	discussion	Taxonomic notes. This study confirms the synonymy of P. d. nigerrimus Sakaino & Yu, 1993 under P. d. cheni Bomans & Ratti, 1973, a classification originally proposed by Huang & Chen (2012). Examination of the holotype of P. d. nigerrimus confirms that the black color morph is structurally identical to the type series of P. d. cheni. The evidence against the validity of P. d. nigerrimus as a separate subspecies is substantial: Firstly, the purported diagnostic black color is merely the extreme end of a polymorphic gradient that exists sympatrically across the geographical range. This color variation is likely induced by developmental or environmental factors, a finding supported by controlled breeding observations. Secondly, regarding distribution, both color forms cooccur in multiple localities, including the type localities (Li-Shan and Pilu), which directly invalidates the use of geographical segregation as a basis for subspecific separation. Finally, although molecular data (Tsai & Yeh 2016) indicate that P. d. nigerrimus and P. d. cheni possess slight genetic differences, this study nevertheless supports the classification proposed by Huang & Chen (2012). The author concludes that this minor difference is insufficient to warrant subspecific distinction and therefore confirms the former as a junior synonym of the latter.	en	Lin, Jing-Zhi (2026): Revision of Prismognathus Motschulsky, 1860 (Coleoptera: Lucanidae) in Taiwan. Zootaxa 5741 (1): 181-191, DOI: 10.11646/zootaxa.5741.1.8, URL: https://doi.org/10.11646/zootaxa.5741.1.8
