Obesoconnus, Jałoszyński, Paweł, 2014

Jałoszyński, Paweł, 2014, Obesoconnus gen. n., a new bizarre Neotropical genus of Cyrtoscydmini (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 3794 (3), pp. 481-491 : 482-485

Obesoconnus gen. n.

Type species: Obesoconnus guyanensis sp. n. (here designated).

Diagnosis. Male and female: body stout, with weakly marked constrictions between head and prothorax, and between prothorax and elytra; head capsule without occipital constriction; antennae gradually thickening distally; submentum demarcated laterally by sutures; hypomeral ridges long but posteriorly not reaching gular plate; maxillary palpomere IV stout, about as long as broad; prothorax with lateral marginal edges; pronotum with transverse antebasal groove connecting two to three small pits (lateral pair present in both known species, and median pit absent in O. mexicanus sp. n.) and with separate lateral antebasal impressions; basal part of prosternum much shorter than coxal part; procoxal sockets narrowly open; prosternal intercoxal process barely marked, with rounded apex; mesoventrite with asetose impressions, without setose impressions; mesoventral intercoxal process keel-shaped; metaventral intercoxal process with deep median notch; each elytron with asetose rudiment of basal fovea.

Male: aedeagus with basal pumping apparatus composed of lentiform sclerotization located in middle of membranous diaphragm and internally connected to longitudinal apophysa providing attachment site for muscles; parameres present, not fused to median lobe.

Description. Body of male ( Figs. 1–2 ) stout and compact, strongly convex, with moderately long and slender appendages, BL 0.90–1.01 mm; cuticle glossy, dark brown and setose.

Head capsule ( Figs. 1–4 ) with anterior part (in front of occiput) transverse, with large and strongly projecting eyes; occipital constriction and tempora absent; vertex ( Fig. 3 ; vt) broader than long, convex, not projecting dorsocaudad; frons ( Fig. 3 ; fr) posteriorly confluent with vertex, with subtrapezoidal anterior part; fronto-clypeal groove absent; antennal insertions broadly separated. Vestiture of head composed only of thin setae, without thick bristles.

Gular plate ( Fig. 4 ; gp) large and distinctly narrowing anterad; gular sutures ( Fig. 4 ; gs) distinct; posterior tentorial pits hidden in transverse groove demarcating gular plate and base of submentum, not visible in ventral view.

Labrum ( Fig. 5 ) transverse with slightly concave anterior margin, with two transverse rows of long setae in pre-apical and apical region. Mandibles ( Fig. 6 ) symmetrical, subtriangular, each with broad base and strongly curved, sharply pointed apex, with broad and short mesal protuberance, without setose prostheca. Each maxilla ( Fig. 7 ) with subtriangular basistipes ( Fig. 7 ; bst), elongate galea ( Fig. 7 ; gal) and lacinia ( Fig. 7 ; lac) and moderately long maxillary palp composed of slightly elongate palpomere I ( Fig. 7 ; mxp1), strongly elongate, pedunculate palpomere II ( Fig. 7 ; mxp2), broad and stout palpomere III ( Fig. 7 ; mxp3) broadest in basal third, and short, subconical and pointed palpomere IV ( Fig. 7 ; mxp4) with distinctly delimited asetose apical part.

Labium ( Figs. 4, 8 ) with elongate submentum ( Fig. 4 ; smn) demarcated laterally from postcardinal parts of hypostomae by lateral sutures ( Fig. 4 ; lss), subtrapezoidal mentum ( Fig. 8 ; mn); and short prementum ( Fig. 8 ; pmn) bearing small three-segmented labial palps ( Fig. 8 ). Hypostomal ridges ( Fig. 4 ; hr) long, extending postero-mesally but not reaching anterior margin of gular plate.

Antennae ( Figs. 1–2 , 4 ) relatively short but slender, loosely assembled, gradually thickening distally.

Pronotum ( Figs. 1–2 ) in dorsal view semi-oval or subtrapezoidal with strongly rounded anterior margin, weakly rounded lateral margins and arcuate posterior margin, without anterior corners, with posterior corners weakly marked, obtuse and blunt. Sides of pronotum with distinct lateral marginal edges visible in posterior half or 3/4; base with transverse groove connecting pair of small and shallow lateral pits and with large but shallow lateral subtriangular impressions near lateral margins and slightly anteriorly to groove, in one species additionally small median pit within antebasal groove can be seen. Sides of pronotum without bristles.

Prosternum ( Fig. 9 ) with short basisternal part ( Fig. 9 ; bst) indistinctly demarcated from procoxal cavities ( Fig. 9 ; pcc) by diffused bisinuate carina; median part of sternum with rudimentary prosternal intercoxal process developed as indistinct protuberance with rounded apex; procoxal sockets ( Fig. 9 ; pcs) nearly closed by narrow postero-lateral lobes of prosternum; hypomera ( Fig. 9 ; hy) elongate, each divided into broad lateral part and narrow internal (adcoxal) part; pronotosternal sutures ( Fig. 9 ; nss) and hypomeral ridges ( Fig. 9 ; hyr) complete.

Mesonotum ( Fig. 10 ) subtriangular, with subrectangular mesoscutum ( Fig. 10 ; sc2) and subtriangular mesoscutellum ( Fig. 10 ; scl2) separated by mesoscutoscutellar suture ( Fig. 10 ; sss). Mesoscutellum largely visible between bases of elytra in intact specimens, with distinct basal impression.

Mesoventrite ( Fig. 11 ) with narrow anterior ridge ( Fig. 11 ; ar); mesoventral intercoxal process ( Fig. 11 ; msvp) narrow and strongly projecting ventrally, anteriorly connected with anterior ridge; asetose lateral impressions of mesoventrite ( Fig. 11 ; ai) present and subtriangular; setose impressions absent; mesanepisternum with moderately long prepectus ( Fig. 11 ; pre) and posterior part largely visible in ventral view; mesepimeron not visible in ventral view; sides of mesothorax without foveae; mesocoxal projections ( Fig. 11 ; mcp) with mesocoxal sockets ( Fig. 11 ; mscs) located on their mesoventral surface, without projecting posterior lobes.

Metanotum ( Fig. 10 ) with alacristae ( Fig. 10 ; alc) reaching posterior margin of notum.

Metaventrite ( Fig. 11 ; v3) slightly transverse, anteriorly fused with mesoventrite, posteriorly shallowly bisinuate and with narrow median subtriangular metaventral intercoxal process ( Fig. 11 ; mtvp) deeply notched in middle. Metanepisterna and metepimera narrow.

Metafurca ( Fig. 11 ) with very short and broad stalk and divergent lateral furcal arms ( Fig. 11 ; lmfa).

Elytra ( Figs. 1–2 ) oval, each with single rudimentary and asetose basal fovea barely discernible in transparent mounts; humeral calli well-marked and developed as longitudinal protuberances; elytral apices separately rounded, in one species with subapical impressions.

Hind wings well-developed, about twice as long as elytra.

Legs ( Figs. 1 , 11 ) moderately long and slender; procoxae subglobose, mesocoxae elongate, metacoxae strongly transverse; all trochanters short; all femora weakly clavate; tibiae short and slightly thickening distally; tarsi slender.

Abdominal sternites unmodified, suture between VII and VIII barely marked.

Aedeagus ( Figs. 12–13 ) sac-shaped, narrowing toward base and apex, with slightly asymmetrical apical part of median lobe, and with variously developed apical projections ( Figs. 14 , 16 ; ap) protruding distally; base of median lobe with pumping apparatus ( Figs. 14 , 16 ; bpa) composed of membranous area with median lentiform sclerotization protruding inside aedeagus as axial apophysis to which oblique longitudinal muscles are attached and extend to aedeagal walls; parameres long and not fused with median lobe, with apical or subapical setae.

Distribution and composition. Obesoconnus is represented by two species known from Mexico and French Guyana ( Fig. 20 ).

Etymology. The name Obesoconnus is derived from the Latin obesus (fat, plump, stout) and a stem - connus common among genera of Cyrtoscydmini . The name refers to the stout body shape. Gender masculine.

Remarks. The strikingly stout and compact body of Obesoconnus and the head capsule without the occipital constriction resemble Paraneseuthia , a genus that belongs to Eutheiini ( Jałoszyński 2014) . However, the conical maxillary palpomere IV with an asetose apical part is characteristic of Cyrtoscydmini , where the new genus is included. Despite the unusual body shape, Obesoconnus does not differ much from other Cyrtoscydmini , and the head not constricted behind the eyes may be a result of a general tendency of broadening and shortening the body, noticeable also in the short antennae and maxillary palps, and the extremely short prosternum.

Among Neotropical Cyrtoscydmini only Alloraphes Franz has the aedeagus with a basal pumping apparatus, i.e., with the basally located membranous diaphragm bearing median lentiform sclerotization projecting internally as a long apophysis, to which internal muscles are attached. The function of this structure was discussed in a recent revision of Alloraphes ( Jałoszyński 2013a) . The aedeagi of Obesoconnus and Alloraphes are highly similar. Outside Central and South America, only Parastenichnaphes Franz , represented by two Oriental species, has the aedeagus with a similar apparatus ( Jałoszyński 2005). However, Parastenichnaphes has the aedeagus devoid of parameres (illustrated in Jałoszyński 2005), which are present in Alloraphes and Obesoconnus . Besides close similarities in genital structures, Alloraphes and Obesoconnus (whose ranges overlap in Central and northern South America) share also the elongate prementum demarcated laterally by sutures; long postcardinal parts of hypostomae demarcated by hypostomal ridges; posterior tentorial pits hidden in the groove demarcating the submentum from gular plate; the pronotum with transverse antebasal groove and lateral edges; the short basisternal part of prosternum indistinctly demarcated from procoxal cavities, which are indistinctly separated by a rudimentary and rounded prosternal intercoxal process; complete hypomeral ridges and pronotosternal sutures; the mesoventrite with asetose impressions behind the anterior ridge but without posterior setose impressions; the narrow mesoventral intercoxal process; and the short metaventral intercoxal process deeply notched in the middle. Differences between these genera are numerous: the body shape (stout and compact in Obesoconnus vs. slender and ‘ant-like’ in Alloraphes ); posterior parts of hypomeral ridges (not reaching gular plate in Obesoconnus vs. extending to gular plate in Alloraphes ); the occipital constriction (absent in Obesoconnus vs. distinct in Alloraphes ); mandibles (without prostheca in Obesoconnus vs. with prostheca in Alloraphes ); maxillary palps (short in Obesoconnus , especially two terminal palpomeres, vs. strongly elongate in Alloraphes ); bristles on sides of prothorax (absent in Obesoconnus vs. present in Alloraphes ); procoxal sockets (narrowly open in Obesoconnus vs. closed in Alloraphes ); mesanepisterna (largely exposed in ventral view in Obesoconnus vs. largely hidden in ventral view in Alloraphes ); and basal elytral foveae (single rudiment in Obesoconnus vs. two rudiments in Alloraphes ).

A relatively short and broad body, and a short maxillary palpomere IV can be found in the genus Plaumanniola Costa Lima, 1962 currently included in the monogeneric and exclusively Neotropical tribe Plaumanniolini. Plaumanniolini and Cyrtoscydmini may be synonyms ( Jałoszyński 2013c), and therefore possible similarities between Plaumanniola and Obesoconnus may be important to clarify the status of Plaumanniolini. At the first sight the body shape of Obesoconnus may appear intermediate between the typically slender and ‘ant-like’ silhouette of nearly all Cyrtoscydmini , and the stout and broad Plaumanniola (illustrated in Jałoszyński 2013c). However, a closer examination reveals a number of important differences, suggesting that Obesoconnus and Plaumanniola are not closely related. The most striking differences are: the broad and stout body of Plaumanniola is not compact, the constrictions between the head and prothorax and the prothorax and elytra are deep (in Obesoconnus the body is more compact, with only weakly marked constrictions); the head capsule in Plaumanniola has a distinct occipital constriction (absent in Obesoconnus ), and more importantly, the sides of submentum are not demarcated from the postcardinal parts of hypostomae (distinct lateral sutures of submentum are present in Obesoconnus ); the procoxal sockets in Plaumanniola are completely closed by broad posterolateral lobes of prosternum (short and narrow lobes in Obesoconnus extend laterally toward hypomera, but do not close the sockets), and the hypomeral ridges are obliterated in the anterior half of prothorax (complete in Obesoconnus ); each elytron in Plaumanniola has two rudiments of basal foveae (one in Obesoconnus ); and the aedeagus of Plaumanniola is devoid of the basal pumping apparatus, instead it has a complex system of internal sclerites and ventroapically located ostium.

Figures

FIGURE 20. Distribution of Obesoconnus gen. n. Obesoconnus guyanensis sp. n. (a) and O. mexicanus sp. n. (b).

FIGURES 1 – 2. Dorsal habitus of holotype males. Obesoconnus guyanensis sp. n. (1) and O. mexicanus sp. n. (2).

FIGURES 3 – 8. Morphology of Obesoconnus guyanensis sp. n. Head in dorsal (3) and ventral (4) views; labrum in dorsal view (5); left mandible in dorsal view (6); left maxilla in ventral view (7); and labium in ventral view (8). Abbreviations: bst, basistipes; cd, cardo; cl, clypeus; fo, foramen occipitale; fr, frons; gal, galea; gp, gular plate; gs, gular suture; hr, hypostomal ridge; lac, lacinia; lhph, lateral lobe of hypopharynx; lp 1 – 3, labial palpomere I – III; lss, lateral suture of submentum; mn, mentum; mst, mediostipes; mxp 1 – 4, maxillary palpomere I – IV; oc, occiput; pmn, prementum; ppf, palpifer; smn, submentum; vt, vertex.

FIGURES 9 – 11. Morphology of Obesoconnus guyanensis sp. n. Prothorax in ventral view (9); pterothorax in dorsal (10) and ventral (11) views. Abbreviations: aest 2, mesanepisternum; ai, asetose impression of mesoventrite; alc, alacrista; ap, apodeme; ar, anterior ridge of mesoventrite; bs, basisternal part of prosternum; hy, hypomeron; hyr, hypomeral ridge; lmfa, lateral metafurcal arm; mcp, mesocoxal projection; mma, median membranous area; mscc, mesocoxal cavity; mscs, mesocoxal socket; msff, mesofurcal fovea; msvp, mesoventral intercoxal process; mtvp, metaventral intercoxal process; nss, pronotosternal suture; pcc, procoxal cavity; pcs, procoxal socket; pf, profurca; pff, profurcal fovea; pre, prepectus; prsc 3, metaprescutum; psn 3, metapostnotum; psp, prosternal intercoxal process; sc 2, mesocutum; sc 3, metascutum; scl 2, mesoscutellum; sss, mesoscutoscutellar suture; v 3, metaventrite.

FIGURES 12 – 15. Aedeagus in ventral (12, 14) and lateral (13, 15) views. Obesoconnus guyanensis sp. n. (12 – 13) and O. mexicanus sp. n. (14 – 15). Abbreviations: ap, apical projection; bpa, basal pumping apparatus.

FIGURES 16 – 19. Aedeagus in ventral (16, 18) and lateral (17, 19) views. Obesoconnus guyanensis sp. n. (16 – 17) and O. mexicanus sp. n. (18 – 19). Abbreviations: ap, apical projection; bpa, basal pumping apparatus.