Elmomorphus cucphuong Selnekovič, Pham & Kodada, 2026, sp. nov.

Elmomorphus cucphuong sp. nov. Figs 10, 11, 19 D Type material. Holotype. Vietnam – Ninh Bình Province • male; Cúc Phương NP [2023 / 16]; 20°21'00.7"N, 105°36'09.5"E; alt. 450 m; 11 May 2023; J. Kodada & D. Selnekovič leg.; CKB, JK 1960. Paratypes. Vietnam – Ninh Bình Province • 13 males, 8 females; same data as for holotype; CKB, IATC, JK 1537, JK 1957 – JK 1959, JK 2407 – JK 2411 • 1 male; Cúc Phương NP [2023 / 19]; 20°19'42.4"N, 105°31'59.9"E; alt. 47 m; 13 May 2023; J. Kodada & D. Selnekovič leg.; CKB, JK 1529. Additional material. Vietnam – Ninh Bình Province • 30 specimens; same data as for holotype • 60 specimens; Cúc Phương NP [2023 / 19]; 20°19'42.4"N, 105°31'59.9"E; alt. 47 m; 13 May 2023; J. Kodada & D. Selnekovič leg.; CKB Type locality. Vietnam, Ninh Bình Province, Cúc Phương National Park, 20°21'00.7"N, 105°36'09.5"E, 450 m a. s. l.; small stream in primary forest on limestone substrate (Fig. 3 D); specimens collected near the spring in accumulations of decaying leaves. Diagnosis. Elmomorphus cucphuong (Fig. 10) is characterised by the presence of a dorsal plastron on the anterolateral portions of the head and pronotum and on the lateral parts of the elytra; nine strongly impressed elytral striae; and the absence of conspicuous long setae on the labrum, the prosternal process, and the median part of the metaventrite in males. This combination of characters is shared with E. bachma sp. nov., E. depressus Selnekovič, Jäch & Kodada, 2024, E. hongkong Selnekovič, Jäch & Kodada, 2024, and E. sulcatus Selnekovič, Jäch & Kodada, 2024. Elmomorphus cucphuong differs from these species in having a wider elytral plastron (Fig. 10) that, in the anterior half of the elytra, extends from the lateral margin to the fourth stria (only to the sixth stria in the other species). Moreover, in E. cucphuong the elytral plastron reaches the elytral base, whereas in the other species it extends only to the humeral callus. The glabrous area on the vertex is smaller and subtriangular in E. cucphuong, whereas it is larger and semicircular in E. sulcatus and E. bachma. In E. cucphuong, only the median portion of the first abdominal ventrite is free of plastron, whereas in E. sulcatus and E. bachma the median portions of the first two ventrites lack plastron. Elmomorphus hongkong further differs from E. cucphuong in having distinctly shallower elytral striae, and E. depressus in possessing a transverse depression on the prosternal process. Elmomorphus cucphuong also differs from all of these species in the shape of the aedeagus (Fig. 11). Elmomorphus cucphuong is readily identifiable by its COI DNA barcode, showing a clear separation from all other examined species in the genus. Its nearest neighbour is E. calvoides, from which it is separated by an interspecific p - distance of 12.59–13.37 %; the maximum intraspecific divergence is 1.98 % (Suppl. material 4). The species is further characterised by unique sequences at the 28 S, ITS 2, and CAD loci. Description. Measurements (mm): TL: ♂♂ 2.35–2.70 (2.52 ± 0.10, n = 14), ♀♀ 2.67–2.90 (2.77 ± 0.08, n = 6); PL: ♂♂ 0.62–0.72 (0.66 ± 0.03, n = 14), ♀♀ 0.67–0.73 (0.70 ± 0.02, n = 6); PW: ♂♂ 1.06–1.25 (1.17 ± 0.05, n = 14), ♀♀ 1.22–1.29 (1.25 ± 0.02, n = 6); EL: ♂♂ 1.74–2.02 (1.89 ± 0.07, n = 14), ♀♀ 1.99–2.13 (2.06 ± 0.05, n = 6); EW: ♂♂ 1.19–1.43 (1.32 ± 0.07, n = 14), ♀♀ 1.38–1.49 (1.42 ± 0.04, n = 6); PhL: 0.35–0.38 (0.37 ± 0.01, n = 8); PrL: 0.26–0.29 (0.28 ± 0.01, n = 8). Habitus (Fig. 10). Body ovate, moderately convex dorsally. Integument dark brown to black; mouthparts, antennae, and tarsi dark reddish-brown. Pubescence consisting of short, sparse, yellowish setae. Plastron present on the head, except for a subtriangular to semicircular area on the vertex; on the anterior angles of the pronotum; on the lateral and posterior portions of the elytra; and on the ventral surface, except for the prosternal process, the median part of the metaventrite, and the median part of abdominal ventrite 1. Head dorsally with round setiferous punctures slightly smaller than the eye-facet diameter, separated by 0.5–1.0 × puncture diameter; surface covered with plastron except for a smooth, subtriangular to semicircular area on the vertex. Labrum transverse, anterior margin shallowly emarginate; exposed portion microreticulated, with small setiferous punctures; setae of equal length in both sexes. Anterior margin of clypeus straight. Eyes oval; interfacetal setae short; ocular index ~ 1.6. Antennae 10 - segmented, densely setose. Pronotum transverse, moderately convex, widest at base; PW / PL: ♂♂ 1.67–1.86 (1.78 ± 0.06, n = 14), ♀♀ 1.72–1.83 (1.80 ± 0.04, n = 6); anterior angles strongly deflexed, prominent and acute; lateral margins convergent anteriorly, evenly rounded; surface smooth, with round setiferous punctures; plastron confined to the anterolateral portions, extending to approx. pronotal mid-length. Prosternal process wider than long; lateral edges divergent and straight; posterior edge rounded; lateral portions strongly raised; median portion moderately convex. Scutellum wider than long, smooth, with round punctures. Metaventral disc flat to weakly convex; the median area free of plastron slightly widened posteriorly. Lateral margins of metaventral process moderately raised. Elytra ovate, widest at approx. the middle; EL / EW: ♂♂ 1.37–1.52 (1.43 ± 0.04, n = 12), ♀♀ 1.40–1.49 (1.45 ± 0.03, n = 6); surface microreticulated with irregular meshes; small setiferous punctures scattered over the entire surface; large punctures arranged in nine longitudinal rows, the punctures within each row confluent; plastron confined to lateral bands extending from the elytral margin to the fourth stria, reaching the elytral base and meeting medially in the posterior third. Tibiae weakly curved; protibia ~ 1.4 × as long as protarsus; terminal protarsomere as long as all preceding tarsomeres combined. Abdominal ventrites covered with plastron except for the median portion of ventrite 1. Ventrite 5 in males with a short longitudinal cluster of dense short setae in front of the apex; in females with a short longitudinal keel in front of the apex, surrounded by longer setae. Aedeagus (Fig. 11): phallobase rather stout, longer than the parameres; PhL / PrL 1.24–1.42 (1.32 ± 0.07, n = 8); parameres moderately wide in lateral view, bent ventrad, with rounded apices; penis rather short, reaching only to ~ 0.7 × the length of the parameres; apex narrowly rounded; sclerotised fibula short and narrow. Bursa copulatrix markedly long, tubular, without microsclerites (Fig. 19 D). Secondary sexual dimorphism. Ventrite 5 in males with a short longitudinal cluster of dense short setae in front of the apex; in females with a short longitudinal keel in front of the apex, surrounded by elongate setae. DNA sequences. Eleven sequences of COI, five of ITS 2, six of 28 S, and five of CAD have been deposited in GenBank and BOLD; accession numbers are listed in Suppl. material 1. Distribution. Vietnam (Ninh Bình Province). Habitat and syntopic taxa. All specimens were collected from accumulations of decaying vegetation in small streams within primary and secondary forest on limestone substrate (Fig. 3 D). Elmomorphus similis was collected at the same sites as E. cucphuong. Etymology. The epithet refers to Cúc Phương National Park in Vietnam, the only locality from which this species is currently known.