Euthygomphus, Kosterin, Oleg E., 2016

Kosterin, Oleg E., 2016, Reconsideration of the genera Merogomphus Martin, 1904, and Anisogomphus Selys, 1857, including erection of a new genus, with a new species and discussion of additional specimens from Cambodia, Zootaxa 4171 (1), pp. 51-76 : 60-61

Euthygomphus gen. nov.

( Figs. 1–11 )

Type species Leptogomphus martini Fraser, 1922 .

Species included (with original genus). Euthygomphus martini (Fraser, 1922) [ Leptogomphus ] comb. nov.; Euthygomphus parvus ( Krüger, 1899) [ Leptogomphus ] comb. nov.; Euthygomphus koxingai (Chao, 1954) [ Anisogomphus ] comb. nov.; Euthygomphus wuzhishanus (Chao, 1982) [ Anisogomphus ] comb. nov.; Euthygomphus chaoi ( Liu 1991) [ Anisogomphus ] comb. nov.; Euthygomphus jinggangshanus ( Liu, 1991) [ Anisogomphus ] comb. nov.; Euthygomphus fujianensis ( Zhou et Wu, 1992) [ Anisogomphus ] comb. nov.; Euthygomphus yunnanensis ( Zhou et Wu, 1992) [ Anisogomphus ] comb. nov.; and Euthygomphus schorri Kosterin, 2016 .

Etymology. As traditional for gomphids, the name, a noun in masculine gender, is composed of two latinised Greek words, the adjective 'euthys' (εύϑύς, meaning ‘straight’, ‘simple’) and ‘Gomphus’ (γόµφος, meaning ‘a nail’).

Diagnosis. Medium sized gomphids with long hind femora extending to distal part of S2, furnished with sparse, even, strong spines, long S8–10, with S10 not shorter than wide, and simple, straight or slightly curved, light-coloured male cerci without processes or protuberances other than apical, but often with a blunt ventrocaudal angle with fine teeth or knobs, and epiproct branches moderately diverging, as cerci or somewhat wider.

Differential diagnosis. The new genus is similar to Merogomphus sensu novo and Anisogomphus sensu novo in main characters including the venation, long hind femora, abdomen with long terminal segments etc. and differs from them in the structure of caudal appendages.

The cerci are:

- in Euthygomphus simple, parallel or slightly diverging, straight or slightly arched in lateral view and/or curved out in dorsal view, without protuberances or processes but small ventrocaudal knobs and/or terminal spine;

- in Merogomphus lyrate (strongly diverging from the base, then converging again), with or without lateral teeth, resembling those of Heliogomphus Laidlaw, 1922 ( Fraser 1934) ;

- in Anisogomphus parallel to each other, although slightly diverging in A. andrei (Lieftinck, 1948) and A. nitidus Yang & Davies, 1996 , with ventral (as a rule) or lateral (in A. yanagisawai Sasamoto, 2015 , and A. neptunus Karube & Kompier, 2016 ) protuberances or processes (but absent in A. pinratani and A. tamdaoensis ); the same in the two other genera of Anisogomphini, Labrogomphus Needham, 1931 , and Notogomphus Selys, 1858 (sublyrate in N. praetorius [Selys, 1878], see Dijkstra & Clausnitzer 2014).

The epiproct branches are:

- in Euthygomphus short, slightly or moderately diverging, to the same extent or slightly more than the cerci; - in Merogomphus strongly divaricate but short, extending but slightly beyond cerci,; - in Anisagomphus large and long, strongly divaricate, extending laterad far beyond cerci in dorsal view; the

same in Labrogomphus and Notogomphus (large but nearly parallel in N. flavifrons Fraser, 1952 , see Dijkstra

& Clausnitzer 2014).

Remarks. The type species of the genus Euthygomphus , Leptogomphus martini , was chosen as the most unambiguous old species, showing the typical structure of the caudal appendages but distinguished by long cornua of V4 and occurrence, without similar species, in East India (e.g. in Khasi Hills in Meghalaya State) ( Fraser 1934, 1940; Lahiri 1987).

In representatives of this genus, the male cerci and hamuli are rather uniform in their structure and can hardly help species identifications. In all species tthe cerci are simple and light-coloured. They are very similar in E. parvus ( Fig. 1 c–d), E. martini ( Fig. 1 a–b), E. chaoi ( Fig. 1 h), E. fujianensis ( Fig. 1 g), and E. yunnanensis ( Fig. 3 a– b,h–i, 5k–m); in E. koxingai they are straight in dorsal view ( Fig. 1 e–f) but arched in lateral view ( Fig. 1 f)); in E. schorri (see below) they are also arched in lateral view but divergently curved in dorsal view and with a strong upright apical spine.

The diagnostic specific characters are readily apparent in the penis distal segment (V4), the general shape of which is variable. In E. martini it is unique for a pair of long cornua (claws) ( Fig. 1 i–j), in E. parvus ( Fig. 1 k) and E. chaoi ( Fig. 1 o) there are a pair of vestigal cornua, and there are no cornua in E. koxingai ( Fig. 1 l–m), E. fujianensis ( Fig. 1 n), E. yunnanensis ( Fig. 3 e,m–n, 4a,c,h–j) and E. schorri (see below). Female diagnostic characters are the occipital ridge and vulvar scale (Fig. 2,3), although neither exhibits much variation.

After transfer of some species into Euthygomphus , the genus Anisogomphus becomes more natural but still seems somewhat heterogeneous and will probably be split into more natural genera in future basing on phylogenetic molecular analysis. This may concern the large species with simple black-coloured cerci without protuberances, A. pinratani and A. tamdaoensis ( Hämäläinen 1991, Karube 2001) or the recently described species with large lateral processes on the cerci, A. yanagisawai and A. neptunus ( Sasamoto 2015, Karube & Kompier 2016). Also the genera Anisogomphus and Notogomphus , or some of their species, may actually be congeneric.

Figures

FIGURE 1. Diagnostic details of males of some Euthygomphus spp. as illustrated in literature: a – h—anal appendages; i – j, l – m, o—distal part of penis (vesica spermalis); k, n—secondary genitalia; a – b, i – j— E. martini (therein considered as Merogomphus martini): a—after Fraser (1934: fig. 95 b); i—after Fraser (1940: plate 3.3); b, j—after Lahiri (1987: fig. 364 – 365,314 – 315); c – d, k— E. parvus (as Merogomphus parvus): c, k—from South Sumatra, Lampoeng residency, Giesting near Talang Padang, Wai Teboe River after Lieftinck (1941: plate 13, fig. 3 – 5); d—from Malay Peninsula, Central Perak, Sungai Plus, near Lasah after Lieftinck (1964: fig. 46); e – f, l – m, p – q— E. koxingai (as Anisogomphus koxingai): e, l, p—the holotype, after Chao (1954: fig. 293 – 297); f, m, q—from China, Guandong after Wilson & Xu (2009: fig. 1 e – g); g, n— E. fujianensis, the holotype of Anisogomphus fujianensis, after Zhou & Wu (1992: fig. 16 – 18); h, o, r— A. chaoi, the holotype of Anisogomphus chaoi, after Liu (1991: fig. 3 – 8). Not to scale; i, b, k mirrored.

FIGURE 2. Diagnostic details of females of some Euthygomphus spp. as illustrated in literature: a – f—occiput; g – k—vulvar scale; a, g— E. parvus, the female syntype of Leptogomphus parvus after Schmidt (1935: Abb. 69 – 70) (therein considered as Merogomphus parvus); b— E. parvus from Malay Peninsula, Selangor, upstream Klang Gates after Lieftinck (1964: fig. 47) (as Merogomphus parvus); c, h— E. koxingai from China, Guandong after Wilson & Xu (2009: fig. 1 k, m) (as Anisogomphus koxingai); d, i— E. wuzhishanus after Chao (1990: fig. 5 – 9.6.1 – 2,4), the holotype of Anisogomphus wuzhishanus; e, j— E. chaoi, the allotype of Anisogompus chaoi, after Liu (1991: fig. 9,12); f, k— E. jinggangshanus, the holotype of Anisogomphus jinggangshanus, after Liu (1991: fig. 13 – 15). Not to scale.

FIGURE 3. Details of Euthygomphus yunnanensis Zhou & Wu, 1992 as illustrated in literature: a – g—after Zhou & Wu (1992: fig. 19 – 25), therein as Anisogomphus yunnanensis, h – t—after Asahina (1986: fig. 25 – 37), therein as Merogomphus parvus (sensu Asahina 1986 nec Krüger, 1899); a – g—the male holotype from China, Yunnan Province, Wandingzhen; h – n—males from Thailand (h – j—from Saraburi Province, Muak Lek); o – t—females from Thailand (p, r—from Mae Hon Son, q, s—from Saraburi Province, Muak Lek) and S. Vietnam, B’Lao; a, h—anal appendages, lateral view; b, i—ditto, dorsal view; c—head, frontal view; j, p, q—ditto, subfrontal view; r – t—occiput enlarged; e—penis (vesica spermalis), lateral view; f—posterior hamulus; g—anterior hamulus; m – n—secondary genitalia, lateral view; l—metafemur; o—end of abdomen, ventral view. Not to scale; a – b and e – g mirrored.

FIGURE 4. Details of secondary genitalia of males of Euthygomphus yunnanensis from Cambodia: a – c—from Mondulkiri Province, ‘ Loringae’ brook downstream of Buu Sraa Waterfalls; d – f—from Koh Kong Province, ‘ Microgomphus River’ 6.5 km SW Thma Bang village; g – k—from Pursat Province, O’Som village; a—general lateral view; b—hamuli, lateral view; d, anterior hamulus, lateral view; e, posterior hamulus, oblique view; c—penis distal segment (V 4), lateral view; f – g—ditto, ventral view; i—ditto, lateral view; j—ditto, dorsolateral view; h—penis (vesica spermalis), lateral view; k—ditto, ventral view. Not to scale.

FIGURE 5. Details of Cambodian specimens of Euthygomphus yunnanensis: a, e, g, k – m—male from Mondulkiri Province, ‘ Loringae’ brook downstream of Buu Sraa Waterfalls; b – d, f – j, n—females: b – c, f, i – j, n—from the same locality, d, h—from Koh Kong Province, ‘ Microgomphus River’ 6.5 km SW Thma Bang village; a – d—thorax, lateral view; e – f—head, frontal view; g – i—occiput, fromtal view; j—ditto, dorsal view; k—male anal appendages, dorsal view; l—ditto, lateral view; m—ditto, ventral view; n—female vulvar scale, ventral view. Not to scale; b, l mirrored.

FIGURE 6. Individuals of Euthygomphus yunnanensis in life: a—mature male, Cambodia, Stung Treng Province, Thala Barivat District, 27 vii 2016; b—teneral female, Cambodia, Koh Kong Province, Thma Bang River 5 km SW Thma Bang village, 366 m a. s. l., 15 iv 2010; c—teneral male, Cambodia, Pursat Province, a river at O’Som village, 12 ° 04 ' 40 – 45 '' N 103 ° 12 ' 21 – 35 '', 524 – 531 m a. s. l., 24 iii 2015. Not to scale.

FIGURE 7. Wings of Euthygomphus yunnanensis (a—male, from Cambodia, Mondulkiri Province, ‘ Loringae’ brook downstream of Buu Sraa Waterfalls, b—female from Cambodia, Koh Kong Province, ‘ Microgomphus River’ 6.5 km SW Thma Bang village) and A. (E.) schorri (c—male holotype, from Cambodia, Mondulkiri Province, 3.5 – 3.8 km ESE of Sen Monorom, ‘ Culminicola Rivulet; d—paratype female 2 from Cambodia, Mondulkiri Province, downstream of Buu Sraa Waterfalls). Not to scale; c mirrored.

FIGURE 8. A male of Euthygomphus schorri photographed in nature in Cambodia, Mondulkiri Province, ‘ Loringae brook’ downstream of Buu Sraa Waterfalls, 10 vi 2014.

FIGURE 9. Euthygomphus schorri, general habitus: a—holotype male; b—paratype female 2 from Cambodia, Mondulkiri Province, downstream of Buu Sraa Waterfalls.

FIGURE 10. Head and thorax of Euthygomphus schorri; a – d—holotype male; e – i—paratype female 2; j—paratype female 1 from the same locality as the holotype; a, f—head and thorax, lateral view; b, g—synthorax, dorsal view; c, h—head, frontal view; d, i—occiput, frontal view; e, j—occipital horns, posterior view. Not to scale.

FIGURE 11. Abdominal structures of Euthygomphus schorri; a – j—holotype male; k—paratype female 2; a—cerci, lateral view; b—ditto, dorsal view; c—ditto, ventral view; d—right cercus, lateral view; e—secondary genitalia, lateral view; fhamuli, lateral view; g—penis distal part segment (V 4), lateral view; h—ditto, dorsal view; i—ditto, oblique view; j—ditto, schematic outline; k—vulvar scale. Not to scale; i mirrored.