Euthygomphus Kosterin, 2016, gen. nov.
Creators: name: Kosterin, Oleg E.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Odonata
Gomphidae
Euthygomphus

description: 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.
description: Published as part of 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, pp. 51-76 in Zootaxa 4171 (1) on pages 60-61, DOI: 10.11646/zootaxa.4171.1.2, http://zenodo.org/record/261686