Siphlonurus orientali s sp. nov. urn:lsid:zoobank.org:act: 2E276F07-489D-402E-BCC1-D878BC22AB2F Figures 11–17 Material examined Holotype: male imago, Chanyuan Temple, Tianmu Mountain, Zhejiang Province, 3–5.IV.2019, Heying Wang, Xiaoli Ying, Wei Zhang and Zhenxing Ma. Paratypes: 50 nymphs, 2♀ imagos, 6♂ imagos, 1♀ subimago, 1♂ subimago, 10 exuviae of nymphs, with same label data as holotype. Additional material Four nymphs, 9♂ imagos, 1♀ subimago, Wuyi Mountain, Fujian Province, 27°39.19'N, 117°57.55'E, ca. 340 m, 17–19.III.2021, Zhenxing Ma, Pengxu Mu, and Dewen Gong; 3 nymphs, 1♀ imago, 1♂ imago, Wuyi Mountain, Fujian Province, 27°38.35'N, 117°57.15'E, ca. 340 m, 12–14.IV.2021, Wei Zhang and Zhiming Lei; 7 nymphs, 1 exuvia of nymph, Yizhan Tea Factory, Mount Wuyi City, Fujian Province, 27°44.55'N, 117°40.41'E, ca. 730 m, 8–13.III.2022, Xuhongyi Zheng and Zhiming Lei. Description Mature nymph (in alcohol, Figs 11–13): Body length 14.0–23.0 mm, cerci 7.0–9.0 mm, length of terminal filament nearly subequal to cerci. Body generally yellowish to amber, marking pattern on dorsal surface complex and varied while marking on ventral surface relatively stable. Legs with distinct dark brown bands (Figs 11A–D). Head: generally yellowish with two pairs of oblique dark brown stripes between ocelli and clypeus and with pair of longitudinal dark brown stripe on vertex. Clypeus dark brown with median yellowish marking. Compound eyes dark grey. Antennae 2.0 mm, length of antennae subequal to width of head, surface of antennae with very sparse setae (Fig. 12A). Mouthparts: totally yellowish. Labrum dark brown with a median pale marking. Galea-lacinia and apical segment of maxillary palp dark brown. Labrum: free margin with row of dense bristle-like setae, additional row of setae near anterior margin dorsally. Ventral surface with scattered short dense bristle-like setae, forming an obvious median groove. Posterolateral corner slightly sclerotized. Length-to-width ratio about 1.0: 2.0 (Fig. 12B). Left mandible: apex of outer incisor divided into four denticles and inner one divided into three denticles, outer incisor wider than inner one. Prostheca composed of a distinct stout spine and tuft of numerous fine spines (Fig. 12C). Right mandible: apex of outer incisors serrated into three denticles while apex of inner one with two denticles. Prostheca constituted by tuft of spines and small spine. Additional tuft of hair-like setae on inner margin near molar (Fig. 12D). Lingua of Hypopharynx round, apical surface with dense short setae. Superlinguae with hair-like setae on apical and lateral margins, inner margins with dense short setae (Fig. 12E). Maxillae: Apex of galea-lacinia divided into three broad canines. Apical margin of galea-lacinia with row of long setae, 10–12 of these setae with comb-shaped apex. Inner margin with two rows of dense long setae and three stout apical dentisetae between them, two obvious dentisetae slightly longer than setae nearby. Several sparse setae scattered on inner margin basally. Three segments of maxillary palp with sparse setae on surface, and setae on apical segment longer. Surface of basal segment scattered with additional short stout spines. Basal segment shorter than galea-lacinia, inner margin of maxillary palp segment II straight, length ratio of three segments ca. 1.0: 0.7: 0.5 (Figs 12F, G). Labium: glossae and paraglossae with dense bristle-like setae on surface, paraglossae semi-circle and broader than glossae. Three segments of labial palp with sparse setae and spines on surface, length ratio of three segments from basal to apical ca. 1.0: 0.8: 0.5 (Fig. 12H). Thorax: nota totally yellowish with symmetric irregular variable spots, wingpads with dark spots (Fig. 11A). Coloration pattern of all legs similar, ground color yellowish, femora with an amber transverse band subapically and a vague amber band basally, tibiae dark basally, tarsi dark apically and basally. Surface of all legs with short sparse spines and setae, patellar-tibial suture on midleg and hindleg clear (Figs 13A–D). Claws slim and pointed, without teeth (Fig. 13B). Length ratio of femora: tibiae: tarsus in all legs similar, ca. 21: 1.0: 1.4. Abdomen: Coloration pattern of abdominal terga changes greatly, and two pairs of dark spots relatively stable: one submedian pair and one lateral pair near lateral margin (Fig. 11A). Each sternum dark sublaterally, with pair of dark brown submedian unfused oblique stripes, very clear in mature nymphs of both sexes (Figs 11B–D). Posterolateral projection of each tergum well developed, progressively larger and wider from tergum I to tergum IX, length ratio of posterolateral spine on tergum IX to its tergum = 1.0: 2.0 (Figs 11E–G). Abdominal sternum IX of both sexes with distinctly convex posterior margin (Figs 11F, G). Dorsal surface and posterior margins of abdominal terga I–IX covered with stout spine-like setae, while ventral surface and posterior margins of abdominal sterna I–IX with smaller, more sparse spine-like setae (Figs 11A–D). Both dorsal surface and margins of tergum X with stout and pointed spine-like setae (Fig. 11H). Gills transparent with distinct yellow trachea, dorsal lamellae of gills I and II and other five gills with sclerotized anterior marginal line, progressively longer from gill I to VII, with vague sclerotized line near middle (Figs 13E–K). Gills I and II similar in size and shape, outer margins of dorsal lamellae of both gills I and II straight, those of ventral lamellae concave, dorsal lamellae all apically pointed, costal rib of dorsal lamella in gill II longer than half of anterior margin (Figs 13E, F). Outer and posterior margins of gill III straight (Fig. 13G). Proximal plate of gill VII well developed (Fig. 13K). Caudal filaments yellowish with two dark brown band subapically and apically. Mesal margins of cerci and both sides of terminal filament with dense hair-like setae (Figs 11A–D). Male imago (in alcohol, Figs 14–15): body length 16.0–18.0 mm, cerci 23.0–25.0 mm, terminal filament 0.1 mm, forewing 15.0–16.0 mm, hindwing 5.0–6.0 mm, antennae 1.5 mm. General coloration yellowish and amber, wings with distinct dark spots and clouds (Figs 14A–C). Head: Compound eyes contiguous, grey and upper 2/3 slightly darker. Ocelli pale with dark base. Antennae light brown with darker scape and pedicle. Thorax: general coloration dark brown. Posterior projection of mesonotum and metanotum distinctly convex (Figs 14D, E). Wings: in area between C, Sc, R 1 and Rs 1 of forewing, all crossveins surrounded with distinct dark brown, with a middle dark brown spot. Rs forked at 1/3 basal, MA forked near middle of wing. MP forked at very base, near the forking point of Rs and MA. Rs and MA fused near base, stem of them further fused with MP. CuA slightly curved backwards, ended at outer margin before tornus, eight veins connecting CuA to hind margin. CuP attached at midpoint of hind margin (Fig. 14B). Apical 2/3 of hindwing washed with light brown, crossveins in this pigmented band tinged with dark brown. A distinct dark brown spot near middle of R 1. MA forked at apical 1/3, MP forked near middle (Fig. 14C). Legs: coxae and trochanters of all legs dark brown, foreleg totally brown with a vague dark brown band apically on femur, midleg and hindleg totally light brown and each with vague dark brown band subapically on femur (Figs 15A, C, D). Each leg with two claws, acute and hooked (Fig. 15B). Length ratio of legs: femur, tibia, tarsus ratio of foreleg = 1.2: 1.0: 2.4; tarsal segments I– V = 2.2: 2.0: 1.8: 1.6: 1.0; femur, tibia, tarsus ratio of midleg = 1.6: 1.0: 1.7; tarsal segments I– V = 3.2: 2.0: 1.5: 1.0: 1.4; femur, tibia, tarsus ratio of hindleg = 1.6: 1.0: 1.6; tarsal segments I– V = 3.8: 2.3: 1.6: 1.0: 1.5. Abdomen: Ground color yellowish. Tergum I light brown. Terga II–IX each with brown triangular-shaped marking on middle line and a pair of dark brown stripes laterally, additional pair of vague dark brown long stripes between median marking and lateral stripes. Sternum I totally dark brown. Sterna II–IX each with pair of unfused oblique dark brown stripes submedially (Figs 14D, E). Posterolateral spines of terga VIII and IX poorly developed (Figs 15E, F), and length of them variable (from 0.1mm to 0.3mm). Genitalia: styliger light brown with a pair of round brown dots ventrally. Posterior margin of styliger slightly concave, with two round convexities laterally. Four segments of forceps uniformly reddish brown, length ratio of them from basal to apical = 1.0: 4.2: 1.0: 0.8. Inner margin of basal segment of forceps without projection. Length of penis subequal to length of styliger (Figs 15E–G). Dorsal elongation of penis brown, nearly straight, with sclerotized outer margin, surface smooth without spines. Dorsal lobes strongly sclerotized, mainly composed of pair of round sclerites and sclerotized transverse band, sclerotized transverse band distinctly convex at middle, inner apex of each round sclerite with a small pointed elongation (Figs 15H–J). Penis lobe pale, with long oblique brown sclerite near inner margin, upper half of penis lobe expanded, length of penis lobe ca. 1.8x width (Figs 15H, I). Cerci light brown to amber, median terminal filament light brown, vestigial. Female imago (in alcohol, Fig. 16): Body length 18.0–20.0 mm, cerci 22.0–27.0 mm, terminal filament 0.1 mm, forewings 17.0–19.0 mm, hindwings 7.0–9.0 mm. Length ratio of forefemur: foretibia: foretarsus= 1.0: 0.6: 1.2; length ratio of foretarsal segments I– V = 1.0: 0.8: 0.6: 0.4: 0.6; length ratio of midfemur: midtibia: midtarsus= 1.0: 0.7: 1.1; length ratio of midtarsal segments I– V = 1.0: 0.8: 0.5: 0.4: 0.7; length ratio of hindfemur: hindtibia: hindtarsus= 1.0: 0.7: 1.1; length ratio of hindtarsal segments I– V = 1.0: 0.6: 0.4: 0.3: 0.6. Color pattern of female similar to male, body reddish brown to dark brown, compound eyes grey to black, ocelli pale with dark base. Foreleg yellowish with dark brown band on femur subapically and on entire tarsus, midleg and hindleg yellowish with dark brown band on femur subapically (Figs 16A–C). Color pattern of wings resembled male, but brown band on hindwing smaller than in male, only outer margin of hindwings pigmented with brown (Figs 16D, E). Color pattern of thorax and abdomen similar to male, but clearer. Tergum I light brown with dark brown lateral margin. Terga II–IX ground color yellowish brown, each sternum with two pairs of dark brown stripes and middle triangular-shaped marking, one pair of stripes on lateral margins and another present submedially. Sternum I totally dark brown. Sterna II–IX each with pair of unfused oblique dark brown stripes submedially. Posterolateral spines of terga VIII and IX relatively short, nearly invisible (Figs 16B, C). Subgenital plate extended posteriorly into a rectangular lobe, subanal plate distinctly convex. Abdominal sternum VIII with pair of unfused oblique stripes (Fig. 16F). Male subimago: Body color pattern same as in male but lighter than in male imago, especially abdominal stripes. Wings semi-hyaline, color pattern similar to male. Genitalia generally similar to those of male imago but penis and forceps shorter and paler. Female subimago: Similar to female imago but body clearer and wings semi-hyaline with additional dark spots on middle of hindwings. Egg: Eggs generally oval (Fig. 17A). Surface nearly smooth but with vortex-like rough circular areas, two micropyles present (Fig. 17B). Etymology: As this new species is found in Zhejiang and Fujian Province, which are located in the southeastern region of the country, the species has been named using the Latin word ‘orientalis’ based on its geographical distribution. Biology: The nymphs mainly inhabit cold slow-flowing waters or pools. They exhibit strong adaptability to environments characterized by low oxygen levels and mild pollution. Distribution: China (Zhejiang and Fujian Province). Diagnosis S. orientalis can be distinguished from other species by following characters. Mature nymph: (1) relatively larger body than others, body length ranges from 14.0 to 23.0 mm; (2) wingpads with spots (Fig. 11A). (3) relatively longer first segment of maxillary palp (ca. 0.8xgalea-lacinia); (4) inner margin of maxillary palp segment II straight (Fig. 12F). (5) length ratio of posterolateral spine on tergum IX to its tergum = 1.0: 2.0 (Figs 11E–G). (6) Each abdominal sternum with a pair of unfused oblique stripes. (Figs 11C, D); (7) Posterior margin of abdominal sternum IX distinctly convex (Figs 11F, G). (8) Both dorsal surface and margins of tergum X with stout and pointed spine-like setae (Fig. 11H). (9) Outer margins of dorsal lamellae of both gills I and II straight while those of ventral lamellae concave, costal rib of dorsal lamella in gill II longer than half of anterior margin (Figs 13E, F). (10) Outer and posterior margins of gill III straight, proximal plate of gill VII well developed (Figs 13G, K). Male imago: (1) Larger body, body length 16.0–18.0 mm; (2) forewing with dark brown crossveins and large dark brown spots between C and Rs 1, hindwings with dots too; (3) leg color patter: forelegs brown, midlegs and hindlegs light brown (Figs 14A–C). (4) each abdominal sternum with a pair of unfused oblique stripes (Fig. 14E). (5) posterolateral spines of abdominal segments VIII and IX relatively small (Figs 15E–G). (6) inner margin of basal segment of forceps without projection, length of penis subequal to styliger (Figs 15E–G). (7) shape and spinal pattern of penes (Figs 15H–J). Female imago: Body size ca. 20.0 mm, wings with dots and sternum VIII with a pair of brown stripes (Fig. 16F). Remarks Siphlonurus davidi, S. dongxi, and S. orientalis sp. nov. are three closely related species, all of them are in southern China. Nymphs of these species are extremely similar in body size, wingpads pigmentation, posterolateral spines of abdominal sterna, and spine-like setae on tergum X, making them difficult to distinguish. However, through detailed morphological comparisons, diagnostic characteristics can be identified: (1) Abdominal sternum markings: S. davidi exhibits a pair of fused reddish-brown oblique stripes on each abdominal sternum (Fig. 3B), while S. dongxi has two pairs of spots, a smaller central pair and a larger posterolateral pair, often fused (Fig. 5B), and S. orientalis sp. nov. displays a pair of unfused oblique stripes (Figs 11C, D); (2) gills: S. davidi and S. orientalis sp. nov. possesses straight outer margins on dorsal lamellae of gills I and II, concave ventral lamellae margins (Figs 3H, I, 13E, F). In contrast, S. dongxi shows straight outer margins on both dorsal and ventral lamellae of gills I and II (Figs 5H, I); (3) Length of basal segment of maxillary palp: in S. davidi, it is equal in length to galea-lacinia (Fig. 3C), whereas in S. dongxi and S. orientalis sp. nov., basal segment is shorter than galea-lacinia (Figs 5C, 12F). The male adults of these species are also highly similar, with nearly identical body size, wing pigmentation patterns, and penis lobe. Diagnostic characteristics are primarily manifested in: (1) Abdominal sternum markings: S. davidi has dark brown anterior and lateral margins on each abdominal sternum (Fig. 4D), S. dongxi features a pair of dark brown stripes near the center of each sternum, each composed of a central spot and a larger posterolateral spot (Fig. 6D), and S. orientalis sp. nov. bears a pair of unfused oblique dark brown stripes (Fig. 14E); (2) Penis lobe length and sclerotization: S. dongxi has penis lobes significantly longer than styliger, with entire dorsal elongation sclerotized (Figs 6E, F, H, I), whereas S. davidi and S. orientalis have penis lobes similar in length to styliger, with only outer margin of dorsal elongation sclerotized (Figs 15E, J); (3) The length-to-width ratio of penis lobes: S. davidi and S. dongxi have a ratio of approximately 1.1–1.2 (Fig. 6I), while S. orientalis sp. nov. has a ratio of approximately 1.8 (Fig. 15I); (4) coloration pattern of legs: S. davidi and S. orientalis sp. nov. have entirely brown forelegs and light brown midlegs and hindlegs (Figs 15A–D), whereas S. dongxi exhibits generally pale legs with distinctly darker ends of femora, tibiae, and distal part of each tarsal segment, appearing brown (Fig. 6A).

Published as part of Qiang, Xin-He & Zhou, Chang-Fa, 2025, The species diversity and phylogeny of the genus Siphlonurus Eaton, 1868 from China (Ephemeroptera: Siphlonuridae), pp. 1-56 in Zootaxa 5711 (1) on pages 20-29, DOI: 10.11646/zootaxa.5711.1.1, http://zenodo.org/record/17882788