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

Elmomorphus calvoides sp. nov. Figs 8, 9, 19 C Type material. Holotype. Vietnam – Ngh ệ An Province • male; Con Cuông District, Pù Mát NP [2023 / 12]; 18°57'52.4"N, 104°48'07.2"E; alt. 285 m; 5–9 May 2023; J. Kodada and D. Selnekovič leg.; CKB, JK 1517. Paratypes. Vietnam – Ngh ệ An Province • 6 males, 11 females; same data as for holotype; CKB, IATC, JK 1482 – JK 1486, JK 1505–1507, JK 1511, JK 1518, JK 1519, JK 1585. Additional material. Vietnam – Ngh ệ An Province • 14 specimens; same data as for holotype • 2 specimens; Con Cuông District, Pù Mát NP [2023 / 14]; 18°57'48.3"N, 104°48'24.3"E; alt. 260 m; 8 May 2023; J. Kodada & D. Selnekovič leg.; CKB. Type locality. Vietnam, Ngh ệ An Province, Pù Mát National Park, 18°57'52.4"N, 104°48'07.2"E, 285 m a. s. l. Partly shaded stream flowing through primary forest, ~ 5–10 m wide, with a substrate of stones and gravel, scattered submerged wood pieces, and accumulations of decaying leaves (Fig. 3 C). Diagnosis. Elmomorphus calvoides (Fig. 8) 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 well-impressed elytral striae bearing large punctures; conspicuous long setae on the male labrum and in two clusters on both the prosternal process and the median part of the metaventrite; and an aedeagus that is remarkably large relative to body length, with a robust, strongly bent phallobase (Fig. 9). Elmomorphus calvoides most closely resembles E. calvus Selnekovič, Jäch & Kodada, 2024. In E. calvus, the elytral plastron is distinctly narrowed anteriad before the elytral base, with the fifth interval entirely free of plastron near the base; in E. calvoides, the elytral plastron is not, or only slightly, narrowed anteriad and extends to the anterior margin in intervals 5–9. The elytral intervals are less convex in E. calvus than in E. calvoides, and the pronotal punctures are coarser and more sharply delimited in E. calvoides. The aedeagus is markedly large and similarly shaped in both species; however, in E. calvoides the parameres are distinctly longer and the phallobase less strongly bent (PhL / PrL: 2.06–2.35, 2.15 ± 0.14, n = 4 in E. calvoides vs 2.34–2.84, 2.62 ± 0.18, n = 7 in E. calvus). Elmomorphus elmoides Selnekovič, Jäch & Kodada, 2024 is also similar to E. calvoides in the extent of the dorsal plastron, the elytral punctation, and the characters of secondary sexual dimorphism, but is readily distinguished by its different body shape (Selnekovič et al. 2024: fig. 21), by the plastron extending along the entire pronotal sides (vs confined to the anterolateral portions in E. calvoides), by the almost straight lateral pronotal margins (distinctly rounded in E. calvoides), and by the shape of the aedeagus, which has a straight phallobase and strongly bent parameres (Selnekovič et al. 2024: fig. 22). Elmomorphus calvoides is readily identifiable by its COI DNA barcode, which shows clear separation from all other examined species in the genus. Its nearest neighbour is E. calvus, from which it is separated by an interspecific p - distance of 5.57–6.34 %; the maximum intraspecific divergence is 0.64 % (Suppl. material 4). The species is further characterised by unique sequences at the ITS 2 and CAD loci, although its 28 S sequences are identical to those of E. calvus. Description. Measurements (mm): TL: ♂♂ 2.90–3.26 (3.13 ± 0.13, n = 6), ♀♀ 3.23–3.52 (3.34 ± 0.09, n = 9); PL: ♂♂ 0.79–0.90 (0.84 ± 0.04, n = 6), ♀♀ 0.84–0.94 (0.88 ± 0.03, n = 9); PW: ♂♂ 1.25–1.41 (1.32 ± 0.06; n = 6), ♀♀ 1.34–1.45 (1.40 ± 0.04, n = 9); EL: ♂♂ 2.17–2.41 (2.33 ± 0.10, n = 6), ♀♀ 2.38–2.64 (2.50 ± 0.08, n = 9); EW: ♂♂ 1.47–1.61 (1.57 ± 0.05, n = 6), ♀♀ 1.61–1.76 (1.66 ± 0.05, n = 9); PhL: 1.00–1.16 (1.06 ± 0.07, n = 4); PrL: 0.48–0.51 (0.50 ± 0.01, n = 2). Habitus (Fig. 8). Body ovate, widest at approx. the middle of the elytra, moderately convex dorsally, with the highest point in the anterior quarter of the elytra. Integument dark brown to black; antennae, mouthparts, and tarsi reddish-brown. Pubescence consisting of short, decumbent, yellowish setae. Plastron present on the head, except for a semicircular area on the vertex; on the anterolateral portions of the pronotum; on the lateral portions of the elytra; and on the ventral surface, except for the prosternal process, the median part of the metaventrite, and ventrite 1. Head with surface covered with plastron except for a smooth semicircular area on the vertex; round setiferous punctures slightly smaller than the eye-facet diameter, separated by ~ 0.5 × puncture diameter. Labrum transverse, anterior margin concave; in males bearing conspicuous long setae. Eyes oval, protruding; interfacetal setae short; ocular index ~ 1.6. Antennae 10 - segmented. Pronotum strongly convex, wider than long; PW / PL: ♂♂ 1.52–1.61 (1.57 ± 0.04, n = 6), ♀♀ 1.54–1.64 (1.59 ± 0.03, n = 9); lateral margins evenly convex; anterolateral angles strongly deflexed and prominent; disc smooth, with round setiferous punctures separated by 0.5–1.0 × puncture diameter; plastron present on the anterolateral portions, extending to approx. pronotal mid-length. Prosternal process with straight lateral margins; lateral portions strongly raised; in males with anterior clusters of long setae; median portion flat in males, weakly convex in females. Metaventral process with raised lateral margins; metaventral disc in males depressed and flat, bearing two posterior clusters of long setae, in females flat and without setal clusters. Scutellum wider than long, smooth, with small setiferous punctures. Elytra moderately convex, widest at approx. the middle; EL / EW: ♂♂ 1.44–1.53 (1.49 ± 0.03, n = 6), ♀♀ 1.47–1.55 (1.51 ± 0.03, n = 9); surface finely microreticulated with irregular meshes, bearing small setiferous punctures scattered over the entire surface; large punctures arranged in longitudinal striae, strial punctures confluent; intervals raised and flat; plastron confined to the lateral portions, reaching to the elytral base and extending from the lateral margin to the fourth stria. Tibiae weakly bent; protibia ~ 1.5 × as long as protarsus; terminal protarsomere as long as the three preceding tarsomeres combined. Abdominal ventrites covered with plastron except for the median portion of ventrite 1, which is delimited by paired longitudinal admedian keels. Ventrite 5 with a short longitudinal keel in front of the apex in both sexes, surrounded by a dense cluster of short, thick, ochraceous decumbent setae followed by a few elongate thin setae; apex weakly produced in males. Aedeagus (Fig. 9): phallobase remarkably long and robust, bent ventrad; PhL / PrL 2.06–2.35 (2.15 ± 0.14, n = 4); parameres weakly bent ventrad, their apices narrowly rounded in lateral aspect; penis rather narrow, acuminate; sclerotised fibula wide. Bursa copulatrix without microsclerites (Fig. 19 C). Secondary sexual dimorphism. Males with elongate erect setae on the labrum and in small clusters on the prosternal process and the metaventral disc; apex of ventrite 5 weakly produced. DNA sequences. Fourteen sequences of COI, six of ITS 2, seven of 28 S, and five of CAD have been deposited in GenBank and BOLD; accession numbers are listed in Suppl. material 1. Distribution. Vietnam (Ngh ệ An Province). Habitat and syntopic taxa. All specimens were collected from a shaded stream in primary forest, with a substrate of small stones and gravel, submerged wood, and accumulations of decaying leaves (Fig. 3 C). The following species were collected at the same site: E. bispinosus, E. paramontanus, E. similis, E. striatellus, E. sulcatus, E. vestitus, Helichus sp., and Stenomystax sp. Etymology. The epithet highlights the striking morphological similarity to E. calvus.