Negragrion sagma gen.n. and sp.n. from South America with a morphological phylogeny of the New World Ischnurinae (Odonata: Zygoptera: Coenagrionidae).

A new coenagrionid genus, Negragrion, is described for N. sagma sp.n. found in Argentina and Brazil (Holotype and allotype, pair in tandem. Argentina: Corrientes: Santo Tomé, arroyo Ita Cuá sobre RP 94, 28°26'48.30"S 56°00'33.11"W, 24.ii.2003, Muzón & Pessacq coll., MLP). The new genus is characterized by the shape of male cerci (decumbent from base; saddle-shaped; in lateral view with an acute apophysis directed dorsally located at 0.3 from base). The presence of a vulvar spine on S8 of females places this genus within Ischnurinae. A cladistics analysis using morphological data was carried out to determine its phylogenetic position. Negragrion gen.n. is recovered within the clade 4 as the sister group of the clade (Acanthallagma Acanthagrion (Oxyagrion, Fluminagrion)).


INTRODUCTION
Coenagrionidae is the most specious family worldwide within the suborder Zygoptera, encompassing almost 1,300 species. In the Neotropical region it is represented by more than 650 species within 70 genera of which 60 are endemic or mainly distributed within the neotropics (Garrison et al. 2010, Dijkstra et al. 2013). This number is continuously increasing; for example, in the last decade 198 new species have been described.
The taxonomy of this family was recently redefined (Dijkstra et al. 2013(Dijkstra et al. , 2014 including within Coenagrionidae the former Pseudostigmatidae and the neotropical members of Protoneuridae. The cosmopolitan Ischnurinae, the largest clade into the core Coenagrionidae, includes all the genera with a vulvar spine on S8, comprising over half of the described species.
In this contribution, a new genus and species of Ischnurinae from specimens collected in Argentina and Brazil are described and diagnosed. A cladistic analysis including all the New World Ischnurinae has been conducted to hypothesized about the position of the genus herein described within Ischnurinae.

MATERIALS AND METHODS
digital camera coupled to the stereomicroscope and an open-source design program (Inkscape version 0.91. at <www.inkscape.org>) and are not to scale. Maps were created electronically using QGIS version 2.16.3.
In order to establish the phylogenetic position of the new genus a data matrix was constructed using as terminal taxa all the New World genera of Ischnurinae as established by Dijkstra et al. (2014). The genus Coenagrion was used as outgroup since it is a basal Coenagrionidae in the analysis performed by Dijkstra et al. (2014). The resulting data matrix is shown in Table I. A list of 32 morphological characters derived from the morphology of adults (head, wing venation, legs, thorax, genital ligula, female terminalia, male cerci and male paraprocts) was elaborated. No larval characters were used since little is known at the generic level for many New World Odonata. The information to assign character states was obtained from literature and direct observation of specimens. The resulting matrix is provided in Table I.
The data matrix was analyzed in the program TNT version 1.5 (Goloboff & Catalano 2016) applying implied weights as optimality criteria. To calculate the appropriate value for constant k a TNT script (propk.run) written by Salvador Arias was used (Spinelli et al. 2018). After running the script, a value of k=6 was obtained for the data set and it was selected for data analysis. To obtain the most parsimonious trees heuristic searches using TBR (Tree Bisection Reconnection) were performed using a Wagner tree as the starting tree, 1000 random addition sequences keeping up 100 trees per replication. Support of clades was evaluated with frequency difference (GC, for "group present/ contradicted") (Goloboff et al. 2003) calculated with 1000 replicates by symmetric resampling of the matrix (not distorted by weights/costs).
ZooBank Life Science Identifier (LSID) -u r n : l s i d : z o o b a n k . o r g : a c t : 4 4 9 B 0 3 7 3 -E98E-412D-95FF-41F89D32D8C6 Etymology. From the Latin "nigrum" in honour of the first author' wife, Susana Claudia Diaz, which nickname is "negra", and "agrion" a neuter noun transliterated from the Greek "agrios" meaning wild, a noun used for many damselfly names.
Diagnosis. Head with frons rounded and postocular spots present. Synthorax light blue with well-defined black stripes. Flexure of genital ligula short (segment 3 longer than flexure height). Segment 3 of genital ligula slender, without lateral lobes; ental surface with a middle subrectangular lobe that reaches segment 2; distal margin with indentation; disto-lateral projections acutely pointed, not surpassing segment 2. Cerci decumbent from base, saddle-shaped; in lateral view with an acute apophysis directed dorsally located at 0.3 from base. Females without mesepisternal fossae, mesostigmal plates wide, with medial margin approximately equal to anterior margin; with a semicircular ridge on posterior margin; with vulvar spine.

Negragrion sagma sp. n.
Etymology. From sagma (Greek) meaning saddle. The name refers to the male cercus shape.
Description of male holotype. H e a d : L a b r u m p a l e b ro w n w i t h posteromedian spot and posterolateral margins black. Anteclypeus greenish light blue; postclypeus black. Antefrons light greenish blue with black T-shaped spot. Dorsum of head mostly light blue, spots as in Fig. 1a Wings (Fig. 1b): Hyaline, pt reddish brown; CuP reaching posterior margin of wing or CuP&AA'; arculus opposite Ax2. FW: Px 9; RP2 beginning between Px4 and Px5; IR1 beginning at Px7; 3-4 cells posterior to pt. HW: Px 8; RP2 beginning between Px3 and Px4; IR1 beginning at Px7; 4-5 cells posterior to pt.
Abdomen: S1: tergum light blue with anterior spot black, subrectangular, posterior margin separated from posterior margin; posterior stripe represented by a lateral J-shaped spot visible in lateral view; sternum pale light blue, with a diffuse dark spot on anterior margin. S2: tergum light blue; dorsal spot subrectangular, anterior margin reaching anterior margin of tergum; posterior margin separated from posterior stripe of S2; posterior stripe in contact with posterior margin of tergum; lateral margins in contact with ventrolateral margins of tergum in lateral view; laterals of tergum with elliptical pale brown spots; anterior lamina pale brown with external margins black; posterior hamulis pale brown. S3 to S7: terga with dorsal spots  subrectangular occupying most of the tergum; anterior margin of spots convex, separated from anterior margin of segments on S3 to S5; laterally reaching half the length of the terga, posterior fifth widened reaching ventral margin of terga; posterior stripes not visible; sterna pale brown with black midventral line, widening towards S7. S8 and S9 (Fig. 1c): terga light blue; posterior bands black, with a row of small spines posteriorly; sterna pale with a mid-ventral black stripe in S8, pale brown with genital valves paler in S9. S10: tergum subquadrangular; black with a small light blue spot visible on lateral view; sternum pale.
Cerci ( Fig. 2c-d): Black, approximately as long as S10; saddle-shaped. In lateral view decumbent from base, with acute apophysis directed dorsally located at 0.3 from base, tip of cerci rounded and pointing dorsally, therefore distal half forming a U-shaped concavity. Distal margin of cerci wide (visible in latero-dorsal view), outer angle rounded, inner angle pointed and directed ventrally. Paraprocts (Fig. 2c): Black. Apophysis short (not reaching tip of cerci), tips acute pointing medially.
Description of female allotype. Colour pattern: similar to that of male holotype. Thorax (Fig. 3a): Posterior lobe of prothorax not projected; mesostigmal plates wide (with medial margin approximately equal to anterior margin), posterior margin with a semicircular ridge; interlaminar sinus subrectangular, projected anteriorly; without mesepisternal fossae. Wings: CuP reaching posterior margin of wing; arculus opposite Ax2. FW: Px10; RP2 beginning at Px5; IR1 beginning at Px8; 4-5 cells posterior to pt. HW: Px 8; RP2 beginning at Px4; IR1 beginning at Px6;5-6 cells posterior to pt. pt pale brown. Terminalia (Fig. 3b): S8 tergum with dorsal black spot that extends posteriorly up to distal third and lateroventrally up to ventral third of tergum in lateral view; the rest is light blue; sternum pale brown with midventral line black; with welldeveloped vulvar spine. S9 tergum with a pair of L-shaped black spots that in lateral view occupy almost all of tergum; rest of tergum light blue. Anterior gonapophyses pale brown; posterior gonapophyses brown; valves surpassing S10 and extending to the tip of cerci; ventral margin slightly concave and serrated. S10 light blue. Cerci slightly shorter than length of S10; in lateral view subtriangular. Paraprocts short, subtriangular in lateral view. Measurements Variation in paratypes. Colour pattern. Aside from small differences in black markings of head and thorax, there is considerable variation in the black markings of S8. Some of the specimens do not have a dorsal black spot (as in the holotype) while in others there is a subrectangular black spot which can occupy from one 0.3 to 0.7 the length of the segment (Fig. 1d-f). Wings. FW: Px 8-10; RP2 beginning between Px4 and Px5 or at Px5; IR1 beginning at Px7 or at Px8; 3-4 cells posterior to pt. HW: Px 7-8; RP2 beginning between Px3 and Px4 or at Px4; IR1 beginning between Px6 and Px7 or at Px7; 4-5 cells posterior to pt. Enallagma) (Apanisagrion, Anisagrion)))). The clade (Apanisagrion, Anisagrion) is well supported (GC= 71) by two synapomorphies, male HW with dense and dark venation (character 3: 1), and presence of paired areas of sclerotized spinules at flexure (character 18: 0).  view with an acute apophysis directed dorsally located at 0.3 from base (Fig. 2c), tip rounded and pointing dorsally; in dorso-medial view widened distally, outer angle rounded, inner angle pointed and directed ventrally. Genital ligula with flexure short (distal segment longer than flexure); segment 3 slender, without lateral lobes; ental surface with a middle sub-rectangular lobe that reaches segment 2; distal margin with indentation; disto-lateral projections acutely pointed not surpassing segment 2. Female mesostigmal plates wide (with medial margin approximately equal to anterior margin); with a semicircular ridge on posterior margin; without mesepisternal fossae; vulvar spine well developed.

DISCUSSION
Phylogenetic relations within Ischnurinae are still poorly supported due to lack of adequate generic characterization and highly homoplaseous characters. A new extensive analysis, including molecular support is needed to firmly resolve the phylogenetic relationships of this subfamily.