Mexiconnus gen. nov.

Type species: Archiconnus mexicanus Franz, 1994: 376 (here designated).

Diagnosis. Male: head short, with vertex not expanded dorso-caudad; thick and long bristles absent on head but present on sides of prothorax; fronto-clypeal groove absent; maxillary palpomere III strongly thickened and stout; mandible with mesal sub-median tooth; antennae with club composed of antennomeres IX–XI; pronotum with rounded sides and weakly arcuate anterior and posterior margins; base of pronotum with deep and distinct transverse ante-basal groove slightly deepened at each end and not reaching lateral pronotal margins, without lateral and sub-lateral carinae; basisternal part of prosternum much shorter than procoxal cavities; prosternum with fine intercoxal carina; prothoracic hypomeral ridges complete; mesoventral intercoxal process long, narrow and strongly expanding ventrally (keel-shaped); mesoventrite with asetose lateral impressions behind anterior ridge, without setose impressions; mesothorax with a pair of deep ventro-lateral foveae; mesocoxal projection with very short, barely discernible posterior lobe; metacoxae narrowly separated by subtrapezoidal metaventral intercoxal process; each elytron with two rudimentary and asetose basal foveae; parameres not fused with median lobe, with broad basal and slender distal parts, without apical setae; internal armature of aedeagus asymmetrical. Females and their diagnostic characters unknown.

Description. Body of male (Fig. 10) moderately strongly convex, slender, with moderately long appendages, BL below 1 mm; cuticle glossy, brown, moderately setose.

Head (Figs. 10, 12) short and approximately rhomboidal, with large eyes; occipital constriction (Fig. 12; occ) in the narrowest place much broader than half HW; tempora long and strongly convergent caudad, without bristles; vertex rounded and convex, broader than long, not expanded dorso-caudad; frons transverse and subtriangular; fronto-clypeal groove absent; antennal insertions broadly separated.

Labrum transverse with rounded sides and nearly straight anterior margin. Mandibles (Fig. 12; md) symmetrical, each with broad basal part, without noticeable prostheca, and with slender and curved distal part with one small subapical mesal tooth. Each maxilla (Fig. 12) with subtriangular basistipes (Fig. 12; bst), elongate galea (Fig. 12; gal) and lacinia (Fig. 12; lac) and moderately long maxillary palp (Fig. 12; mxp) composed of relatively long palpomere I, strongly elongate, pedunculate palpomere II, moderately elongate, very broad palpomere III broadest near middle, and small, subconical palpomere IV.

Labium (Fig. 12) with approximately hexagonal, elongate submentum (Fig. 12; smn) indistinctly delimited from gular plate (Fig. 12; gp) and laterally demarcated from hypostomae by long and recurved lateral sutures of submentum (Fig. 12; lss); subrectangular mentum (Fig. 12; mn); and short prementum with small 3-segmented labial palps (Fig. 12; lp) narrowly separated at bases. Hypostomal ridges (Fig. 12; hr) short, not reaching lateral margins of submentum.

Gular plate (Fig. 12; gp) indistinctly demarcated, strongly narrowing anterad; gular sutures (Fig. 12; gs) superficial; posterior tentorial pits (Fig. 12; ptp) distinct and located at base of submentum.

Antennae (Fig. 10) with club composed of antennomeres IX–XI.

Pronotum (Fig. 10) in dorsal view oval, with indistinct front angles and well-marked hind angles; sides strongly rounded; base of pronotum with deep transverse ante-basal groove slightly deepened at each end and not reaching lateral pronotal margins, without lateral carinae or edges and without sub-lateral carinae; sides of pronotum with long and thick bristles.

Prosternum (Fig. 13) with basisternal part (Fig. 13; bs) relatively short and indistinctly demarcated from procoxal cavities (Fig. 13; pcc); median part of sternum with fine prosternal intercoxal carina (Fig. 13; pc); procoxal sockets (Fig. 13; pcs) closed by lateral lobes of sternum; hypomera (Fig. 12; hy) elongate, each with elongate internal (adcoxal) part demarcated laterally by complete hypomeral ridge (Fig. 13; hyr); pronotosternal sutures (Fig. 13; nss) entire.

Mesoscutellum very small, subtriangular and elongate, barely visible between bases of elytra; mesoscutoscutellar suture fine but discernible.

Mesoventrite (Fig. 14) with narrow anterior ridge (Fig. 14; ar) with small median projection (Fig. 14; par); mesoventral intercoxal process (Fig. 14; msvp) narrow and keel-shaped; mesoventrite behind anterior ridge with sharply delimited lateral asetose impressions (Fig. 14; ai); prepectus (Fig. 14; pre) long, posterior portion of mesanepisternum only partly visible in ventral view; mesepimeron not visible in ventral view; mesothorax with deep ventro-lateral fovea at each side (Fig. 14; vlf); mesocoxal projections (Fig. 14; mcp) with mesocoxal sockets (Fig. 14; mscs) located on their meso-ventral surface, without posterior lobes.

Metaventrite (Fig. 14; vIII) strongly transverse, anteriorly fused with mesoventrite, posteriorly moderately deeply bisinuate and with narrow median subtrapezoidal metaventral intercoxal process (Fig. 14; mtvp) bearing median notch. Metanepisterna and metepimera narrow, only posterior parts of episterna visible in ventral view.

Metafurca (Fig. 14) with very short and broad stem and divergent lateral furcal arms (Fig. 14; lmfa).

Elytra (Fig. 10) oval, each with two rudimentary and asetose basal foveae barely discernible even in transparent mounts; humeral calli well-marked and developed as longitudinal protuberances; elytral apices unmodified, separately rounded.

Legs (Figs. 10, 13–16) long and slender; procoxae subglobose, mesocoxae slightly elongate, metacoxae transverse, stout; all trochanters short; all femora weakly clavate; tibiae short and slightly expanded near middle; tarsi short and stout, protarsi (Figs. 15–16) strongly broadened at base and narrowing distally, with long and dense setae on ventral surface, especially tarsomere I with dense cushion of long setae.

Abdominal sternites (Fig. 14) only partly preserved in holotype; sternites III and IV unmodified.

Aedeagus (Figs. 17–18) strongly elongate, thin-walled, with internal armature composed of moderately darkly sclerotized and tubular structure forming an open loop, and with free (i.e., not fused with median lobe) parameres without apical setae; basal part of parameres very broad and embracing laterally median lobe, distal parts slender and narrowing to pointed apices.

Distribution and composition. Mexiconnus is represented by a single species known from the southernmost part of Mexico.

Remarks. Mexiconnus differs from Archiconnus in several important characters that justify its separate placement. The submentum in Mexiconnus is demarcated from post-cardinal parts of hypostomae by complete lateral sutures and hypostomal ridges are short and posteriorly reaching only to half length of submentum, while in Archiconnus lateral sutures of submentum are absent and the hypostomal ridges are not only long, but connected in middle between the base of submentum and the gular plate. In Mexiconnus the prosternal intercoxal carina is present and the internal parts of prothoracic hypomera are laterally demarcated by complete hypomeral ridges, while in Archiconnus the prosternal carina is absent and the hypomeral ridges are incomplete. In Mexiconnus the mesoventrite has deep ventro-lateral foveae, entirely missing in Archiconnus . Mexiconnus has two rudimentary and barely discernible in transparent mounts basal elytral foveae, while only a single, also rudimentary fovea can be seen in Archiconnus . Also the aedeagi, described by Franz (1994) as similar, differ significantly in the shape of parameres. In Mexiconnus the parameres are massive and their broad basal parts embrace the median lobe laterally, while distal parts are slender and gradually narrowing towards pointed apices devoid of setae. In Archiconnus the parameres are slender also in their basal halves, each with rounded apex bearing two very long and thick setae. Strongly broadened protarsi in the only known male of Mexiconnus mexicanus may constitute another difference between these two genera, as in Archiconnus male and females do not differ in the shape of protarsomeres.

Mexiconnus clearly differs from other members of the hitherto revised genera of the ' Euconnus complex'. From Euconnus s. str. (Jałoszyński 2012) it differs in more slender body, with elytra not so much broader than the pronotum, the lack of fronto-clypeal groove (present in Euconnus s. str.), presence of lateral sutures of submentum (absent in Euconnus s. str.), short hypostomal ridges (long in Euconnus s. str.), pronotum in dorsal view strongly rounded (bell-shaped in Euconnus s. str.), presence of prosternal intercoxal carina (absent in Euconnus s. str.), lack of sub-lateral pronotal carinae (present in Euconnus s. str.), asetose impressions of the mesoventrite (setose in Euconnus s. str.), nearly contiguous metacoxae (moderately broadly separated in Euconnus s. str.), rudimentary basal elytral foveae (deep in Euconnus s. str.), and the broad parameres devoid of apical setae (slender and with setae in Euconnus s. str.).

Mexiconnus differs from Euconnomorphus (Jałoszyński 2012) in the vertex not expanded dorso-caudad (strongly subconical in Euconnomorphus), short and stout maxillary palpomere III (strongly elongate in Euconnomorphus), antennae with distinct club (gradually thickened distally in Euconnomorphus), presence of lateral sutures of submentum (absent in Euconnomorphus), short hypostomal ridges (long in Euconnomorphus), pronotum in dorsal view strongly rounded (bell-shaped in Euconnus s. str.), presence of prosternal intercoxal carina (absent in Euconnomorphus), complete prothoracic hypomeral ridges (incomplete in Euconnomorphus), welldemarcated asetose impressions of the mesoventrite (not demarcated in Euconnomorphus), and two (and not one) rudiments of basal elytral foveae.

Mexiconnus differs from Venezolanoconnus in much more slender body, antennal club composed of three antennomeres (antennae gradually thickening distally in Venezolanoconnus), presence of lateral sutures of submentum (absent in Venezolanoconnus), short hypostomal ridges (long in Venezolanoconnus), pronotum in dorsal view strongly rounded (in Venezolanoconnus strongly rounded in anterior half and weakly in posterior half)), presence of prosternal intercoxal carina (absent in Venezolanoconnus), two (and not one) rudiments of basal elytral foveae, and strongly elongate distal halves of parameres (broad and short in Venezolanoconnus).

Mexiconnus differs from Parapseudoconnus in the presence of lateral sutures of submentum (absent in Parapseudoconnus), postero-lateral (postcoxal) parts of prosternum separated from internal parts of prothoracic hypomera (fused in Parapseudoconnus), two rudiments of basal elytral foveae (one deep and setose fovea in Parapseudoconnus), and presence of parameres (absent in Parapseudoconnus).