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).