Ophiogomphus (Ophionurus) phantoani, Ngo & Nguyen, 2021

Ngo, Quoc Phu & Nguyen, Minh Ty, 2021, The genus Ophiogomphus Lieftinck, 1964 in Vietnam, with descriptions of the female of O. minimus Karube, 2014 and O. phantoani sp. nov. (Odonata: Gomphidae), Zootaxa 5061 (1), pp. 134-144 : 136-139

Ophiogomphus (Ophionurus) phantoani sp. nov.

( Figs 4–11 , 14 , 15, 17, 19, 24, 25, 32, 33)

Holotype: ♂, Song Thanh National Park (15.5080 N, 107.4720 E, altitude 1105 m), Dak Re Commune, Nam Giang District, Quang Nam Province, central Vietnam, 28.vi.2020, Q.P. Ngo leg.

Paratypes: 1 ♀ (in copula with holotype male), same data as holotype, both in ZCDTU ; 1 ♀, Song Thanh National Park (15.3113 N, 107.9097 E, altitude 725 m), Phuoc Kim Commune, Phuoc Son District, Quang Nam Province, central Vietnam, 12.vii.2018, Alisa J. & Thomas W. Donnelly leg., Rosser W. Garrison Collection, USA .

Etymology. The new species is named in honor of Dr. Phan Quoc Toan, a Vietnamese odonatologist, for his great contribution to the knowledge of Southeast Asian Odonata (noun in genitive case).

Description of holotype male

Head ( Figs 4 , 6, 8 ). Labium black, labrum black with a pair of greenish yellow markings at dorso-lateralyl; anteclypeus greenish yellow; postclypeus black with a small yellow spot at dorso-laterally; frons broadly marginated with yellow fascia lying interrupted medially with black; antennae black, yellowish basally; vertex black with two rounded prominences near lateral ocelli. Occiput black, prominent centrally.

Thorax ( Fig. 4 ). Prothorax entirely black. Synthorax mostly black with greenish yellow markings; pale antehumeral stripe and not connected with collar stripe; humeral stripe absent; dorsal carina and post-ventral part of mesinfraepisternum with yellow markings; median part of mesepimeron with pale stripe about half as wide as combined black antehumeral and humeral stripes; a small mid-dorsal yellow stripe on metepisternum; metepimeron largely greenish yellow, anterior and ventral borders black.

Legs ( Fig. 4 ). Legs stoutly built, entirely black. Femur and tibia thick and robust with closely set, gradually lengthening spurs apically. Coxa of front legs black with greenish yellow.

Wings ( Fig. 4 ). Wings hyaline, with brown patches at wing base; anal loop 2-celled; nodal index: Ax/Px = 17/18 (FW) and 12/19 (HW); Pt dark brown, 4.5–5 mm length in both wings, covering about 5 or 6-celles.

Abdomen ( Fig. 4 ). Black with greenish yellow markings; S1 with a medio-ventral spot connecting with postventral spot; S2 with two large lateral spots, one on auricle, the other along posterior carina; S3–6 mostly black each with a narrow basal ring; S7 with a basal spot covering about half of the segment; S8–10 entirely black.

Anal appendages ( Figs 10, 11 ). Entirely black; cercus broad basally, narrower apically, gently curving ventroposteriorly, apex hooked with a dorsal small tooth near the base of cercus. Epiproct curved posterodorsally, subequal in length to cerci with a small dorsal tooth approximately at basal third.

Accessory genitalia ( Fig. 24 ). Anterior hamulus broad medially, abruptly attenuate with apical half strongly curved posteriorly. Posterior hamulus broad basally, narrower and slightly curved cephalad at apex.

Vesica spermalis ( Figs 14 , 15, 25). Prepuce protruded ventroposteriorly, its stem slender; posterior lobe of vesica spermalis slender and short. Cornua of glans with two long, acute V-shaped flagellae ( Fig. 25 ).

Measurements (in mm). Abdomen (including appendages) 40; HW 33.

Description of a paratype female

Colour pattern similar to that of holotype male apart from the following characters:

Head ( Figs 5 , 7, 9 , 17 , 32 ). The greenish yellow markings on dorsal frons much narrower ( Fig. 9 ), ( Fig. 8 ); occiput flattened, a projection medially on occipital crest as shown in Figs. 17 and 32 , its dorsal surface minutely serrate.

Thorax ( Fig. 5 ). Prothorax entirely black. Synthorax robust, yellow making same as in holotype but lacking small mid-dorsal yellow patch on metepisternum.

Wings ( Fig. 5 ). Wings hyaline, with dark brown patches at the base; nodal index:Ax/Px = 17/21 (FW) and 12/21 (HW); Pt dark brown, 4.5–5 mm length in both wings, covering about 5–7 cells.

Abdomen ( Fig. 5 ). S1 with lateral triangular patch; lateral S2 laterally with a large greenish yellow marking; S3–6 each with a pale basal ring; anterior fourth of S7 yellow; S8–10 entirely black.

Anal appendages ( Figs 19 , 33 ). Cerci as the length of S10, dark yellowish, slender, parallel, pointed at tip. Vulvar lamina triangular-shaped, incised apically but not forming a gap.

Measurements (in mm). Abdomen (including appendages) 30 mm. HW 48 mm.

Differential diagnosis. Among the known species of the genus Ophiogomphus , the new species shares the following characters with O. longihamulus , O. minimus and O. sinicus , i.e. large pincer-like appendages with cerci curving posteroventrally and epiproct curving posterodorsally, with apex notched ( Figs 10, 12 ).

Ophiogomphus phantoani can be distinguished from the other congeners by the following characters: In the male, the cornua of glans has two long, acute widely separated, V-shaped flagella ( Fig. 25 ), whereas they are relatively short, U-shaped flagella in O. longihamulus ( Fig. 21 ), O. minimus ( Fig. 23 ) and O. sinicus ( Fig. 27 ); anterior hamulus of O. phantoani with well-developed developed posterior shoulder ( Fig. 24 ) shoulder smaller in O. longihamulus ( Fig. 20 ), O. minimus ( Fig. 22 ) and O. sinicus ( Fig. 26 ).

In the female, the occiput of O. phantoani has a projection with two prominent dorsally microserrated branches ( Fig. 32 ), more widely branched than in O. longihamulus ( Fig. 28 ), O. minimus ( Fig. 30 ) and O. sinicus ( Fig. 34 ); the vulvar lamina of O. phantoani differs from the other species by a pointed tip ( Fig. 33 ), which is incised apically but not widely opened as in the other species ( Figs 29, 31, 35 ).

Habitat and ecology. Ophiogomphus phantoani was found on a small, slowly running, densely vegetated stream (about 1–2 m wide) within pristine forest. The stream originates from a marsh with muddy bottom. The new species shares the same habitat with Coeliccia schorri Phan & To, 2019 ; C. scutellum Laidlaw, 1932 ; Rhinocypha watsoni van Tol & Rozeendal, 1995 ; Burmargiolestes sp. ; Mnais mneme Ris, 1916 ; Orthetrum glaucum (Brauer, 1865) ; Anotogaster chaoi Zhou, 1998 ; Lamelligomphus camelus Martin, 1904 and Merogomphus pavici Martin, 1904 .

Distribution ( Fig. 36 ). Vietnam: Quang Nam Province (Song Thanh National Park).

Figures

FIGURES 14–15. Genital structures of Ophiogomphus phantoani sp. nov. holotype ♂; (14), vesica spermalis, lateral view; (15), apical segment of vesica spermalis, dorsal view.

FIGURE 36. Distribution map of four Ophiogomphus spp. in Vietnam. O. longihamulus (red circle); O. minimus (purple circle); O. phantoani sp. nov. (yellow circle); O. sinicus (green circle). Map background source © GoogleTM Earth Service version 7.3.3.7786.

FIGURES 4–5. Habitus of Ophiogomphus phantoani sp. nov. (4), holotype ♂; (5), paratype ♀. Scale bar is 1 cm.

FIGURES 6–9. Head of Ophiogomphus phantoani sp. nov. in frontal and dorsal view. (6, 8), Holotype ♂ & (7, 9), Paratype ♀.

FIGURES 10–13. Appendages Ophiogomphus spp. in lateral and dorsal view. (10, 11), O. phantoani sp. nov., holotype ♂; (12, 13), O. sinicus, Cao Bang Province.

FIGURES 20–27. Accessory genitalia [20, 22, 24, 26] in lateral view and cornua of glans [21, 23, 25, 27] in ventral view of Ophiogomphus spp. (20–21), O. longihamulus (rearranged from Karube 2014: Fig. 16 e, g); (22, 23), O. minimus (rearranged from Karube 2014: Fig. 18 e, g); (24, 25), O. phantoani sp. nov.; (26, 27), O. sinicus, Cao Bang Province.

FIGURES 16–19. Posterior head and vulva lamina of Ophiogomphus spp., ♀. (16, 18), O. minimus & (17, 19), O. phantoani sp. nov.

FIGURES 28–35. Female occiput [28, 30, 32, 34] & abdominal end [29, 31, 33, 35] in ventral view of Ophiogomphus spp. (28, 29), O. longihamulus (rearranged from Karube 2014: Fig. 16 j, k); (30, 31), O. minimus, Nam Nung Nature Reserve; (32, 33), O. phantoani sp. nov.; (34, 35), O. sinicus (rearranged from Chao 1990: Fig. 10 & Zhang 2019: p. 424).