Zeanichnus, Jałoszyński, Paweł, 2013

Jałoszyński, Paweł, 2013, Revision of subgenera of Stenichnus Thomson, with review of Australo-Pacific species (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 3630 (1), pp. 39-79 : 57-61

Genus Zeanichnus gen. nov.

Type species: Scydmaenus insignis Broun, 1893 (here designated).

Diagnosis. Eyes located posteriorly; occipital constriction nearly as broad as vertex or only slightly narrower; fronto-clypeal groove absent; mandibles subtriangular, with subapical tooth on mesal margin; submentum subtriangular, with very short posterior margin and sinuate lateral margins, completely demarcated from hypostomae by lateral sutures; hypostomae elongate and demarcated from genae only in short anterior parts by incomplete hypostomal ridges; posterior tentorial pits hidden in deep groove between submentum and gular plate; antennae with 4–segmented club or gradually thickened distally; pronotum with one pair of lateral ante-basal pits connected by transverse groove, without lateral marginal carinae or edges; prosternum with narrow basisternal part not demarcated from procoxal cavities, procoxal cavities separated in middle by fine carina; hypomera not demarcated from pronotum; mesoventrite without asetose impressions and with lateral setose impressions narrowly separated in middle and broadly separated from mesocoxal cavities; mesoventral intercoxal process moderately narrow and moderately projecting ventrally, with distinct posterior tip separated from metaventrite; mesocoxal projections with posterior lobes; metaventrite with metaventral anterior process, with short and broad metaventral intercoxal process bearing median notch; aedeagus with free parameres.

Description. Body ( Figs. 62–63 ) strongly convex, strongly elongate and slender, with long appendages, cuticle glossy, distinctly setose.

Head ( Fig. 69 ) subtriangular, broadest at posteriorly located eyes; neck region short and subcylindrical, only slightly broadened in middle; occipital constriction ( Fig. 69 ; occ) in the narrowest place nearly as wide as vertex; tempora ( Fig. 69 ; tm) much shorter than eyes; vertex and frons between eyes confluent and convex, fronto-clypeal groove absent.

Labrum transverse with rounded sides and anterior margin.

Mandibles symmetrical, each with broad basal part and moderately slender distal part, mesal margin with median tooth.

Each maxilla with elongate galea and lacinia ( Fig. 69 ; gal, lac) and long maxillary palp ( Fig. 69 ; mxp) composed of minute palpomere I, strongly elongate and broadening distally palpomere II, long and pedunculate palpomere III nearly equally broad from middle to apex, and slender, elongate subconical and pointed palpomere IV.

Labium with subtriangular submentum ( Fig. 69 ; smn) with sinuate lateral margins and very short posterior margin demarcated from gular plate ( Fig. 69 ; gp) by deep transverse groove in which posterior tentorial pits are hidden, laterally demarcated from hypostomae ( Fig. 69 ; h) by lateral sutures ( Fig. 69 ; lss); mentum subtrapezoidal ( Fig. 69 ; mn); prementum short with broadly separated, small 3-segmented labial palps ( Fig. 69 ; lp). Laterally mouthparts are demarcated from genae only anteriorly by short, incomplete hypostomal ridges ( Fig.69 ; hr).

Gular plate ( Fig. 69 ; gp) large and trapezoidal in shape, with distinct gular sutures ( Fig. 69 ; gs).

Antennae ( Figs. 62–63 ) with club composed of four antennomeres ( Z. insignis ) or gradually thickened distally ( Z. kuschelianus ).

Prothorax ( Figs. 67–68 ) in dorsal view with rounded anterior and lateral margins of pronotum, at base with transverse groove connecting one pair of lateral ante-basal foveae, without lateral marginal carinae or edges; hypomera ( Figs. 67–68 ; hy) not demarcated from notum. Prosternum ( Figs. 67–68 ) with very short basisternal part; procoxal cavities ( Figs. 67–68 ; pcc) without anterior marginal carina, separated in middle by fine prosternal intercoxal carina; procoxal sockets ( Figs. 67–68 ; pcs) nearly closed by lateral expansion of sternum; notosternal sutures ( Figs. 67–68 ; nss) complete.

Mesoventrite ( Figs. 67–68 ) with narrow anterior ridge, without lateral asetose impressions and with moderately large setose impressions ( Figs. 67–68 ; si) narrowly separated in middle and broadly separated from mesocoxal cavities ( Figs. 67–68 ; mscc); mesocoxal projection ( Figs. 67–68 ; mcp) without carina and with posterior lobe ( Figs. 67–68 ; pl) bearing dense setae along posterior margin; mesoventral intercoxal process ( Figs. 67–68 ; msvp) moderately narrow, with distinct posterior tip separated from metaventrite.

Metaventrite ( Figs. 67–68 ) broader than long, with metaventral anterior process ( Figs. 67–68 ; mtap); metaventral intercoxal process ( Figs. 67–68 ; mtvp) broad and short, with distinct median notch.

Elytra ( Figs. 62–63 ) oval, with well-marked humeral calli; each elytron with one rudimentary basal fovea barely noticeable in dry-mounted specimens. Hind wings well-developed.

Legs ( Figs. 62–63 ) long and slender; femora clavate, tibiae nearly straight, tarsi strongly elongate.

Abdominal sternites VII and VIII separated by indistinct suture.

Aedeagus ( Figs. 70–73 ) with complex and symmetrical internal armature composed of sub-basally or submedially located voluminous central complex and sub-apical lateral groups of needle-like sclerites; apical part of dorsal wall forming strongly projecting distally, narrow projection; parameres free and slender, with apical setae.

Distribution and composition. Two species are known to occur in the North Island of New Zealand.

Etymology. The genus name is a combination of "Zea-" derived from New Zealand and "-nichnus" derived from Stenichnus .

Remarks. Broun (1893) in the description of Scydmaenus insignis stated that "I have little doubt it will become the type of a new genus". This opinion is confirmed here and supported by a number of characters that define the new genus, Zeanichnus . Zeanichnus is unique among Cyrtoscydmini in having the submentum strongly narrowing caudad, with sinuate lateral margins and very short posterior margin, as short as about half length of the anterior margin of gular plate, and in having incomplete hypostomal ridges, well-developed only in their anterior parts. The lack of asetose impressions of the mesoventrite differentiates Zeanichnus from all other genera and subgenera revised in the present paper. Austrostenichnus , in which Z. insignis and Z. kuschelianus were previously placed, differs from Zeanichnus in a large number of other characters, e.g., in having confluent procoxal cavities (separated by carina in Zeanichnus ) and carina demarcating procoxal cavities from the basisternal part of prosternum (absent in Zeanichnus ); the setose impressions of mesoventrite broadly separated in middle (narrowly in Zeanichnus ); a broad mesoventral intercoxal process posteriorly fused with the metaventrite (narrow and posteriorly separated from metaventrite in Zeanichnus ); and the lack of metaventral anterior process (present in Zeanichnus ) (differences are compiled in Table 1 ).

It was not possible to examine details of the mandibles (especially their proximal parts) and prementum in the fragile holotypes available for the study. The general shape of the mandible in Zeanichnus seems to be similar to that of Austrostenichnus and Scydmaenilla , i.e., a broad base, abruptly demarcated from a moderately slender apical part bearing a subapical tooth on the mesal margin. The subapical mandibular tooth was well-visible, but the basal part of mandibles, concealed by maxillae, were not visible well enough to describe their shape. Labial discs on the prementum were also not found, but the broadly separated bases of labial palps and lack of a median pair of long bristle-like sensilla (typically located between the palps in many Cyrtoscydmini ) suggest that the prementum may be modified in a similar way as in Stenichnus . However, additional specimens are necessary to examine the mouthpart morphology in detail.

Zeanichnus insignis and Z. kuschelianus differ strikingly in the structure of the antennae. The former species has slender antennae with 4-antennomere club, while Z. kuschelianus has massive antennae with elongate antennomeres I–III, and nearly spherical or transverse antennomeres IV–X. Such big differences in the shape and composition of the antennal club are rare within genera of Cyrtoscydmini and if they occur, then usually are used as subgeneric diagnostic characters. However, both species from New Zealand share many character states associated with the head capsule, prothorax, pterothorax, elytra and aedeagus. Especially their aedeagi are highly similar, making it possible to interpret various parts (e.g., the strongly narrowing apex of dorsal wall, sub-apical lateral groups of needle-like sclerites, various components of the central complex) as homologous and clearly suggesting close evolutionary relationships.

Figures

FIGURES 62 – 66. Zeanichnus insignis (Broun), holotype male (62, 65) and Zeanichnus kuschelianus (Franz), holotype male (63 – 64, 66). Dorsal (62 – 63) and ventral (64) habitus and original set of labels (65 – 66).

FIGURES 67 – 73. Zeanichnus insignis (Broun), holotype male (67, 70 – 71) and Zeanichnus kuschelianus (Franz), holotype male (68 – 69, 72 – 73). Venter (67 – 68), head in ventral view (69), aedeagus in ventral (70, 72) and lateral (71, 73) views. Abbreviations: aest 2, mesoanepisternum; bst, basistipes; cd, cardo; gal, galea; gp, gular plate; gs, gular suture; h, hypostoma; hr, hypostomal ridge; hy, hypomeron; lac, lacinia; lb, labrum; lp, labial palp; lss, lateral suture of submentum; mcp, mesocoxal projection; mn, mentum; mscc, mesocoxal cavity; msvp, mesoventral intercoxal process; mtap, metaventral anterior process; mtfa, metafurcal arm; mtvp, metaventral intercoxal process; mxp, maxillary palp; nss, notosternal suture; occ, occipital constriction; pcc, procoxal cavity; pcs, procoxal socket; pl, posterior lobe of mesocoxal projection; pre, prepectus; si, setose impression of mesoventrite; smn, submentum; tm, temple; v 3, metaventrite.