Papuamicrus, Jałoszyński, 2023

Jałoszyński, Paweł, 2023, Papuamicrus gen. n., a new genus of Cephenniini from New Guinea (Coleoptera: Staphylinidae: Scydmaeninae), Zootaxa 5339 (5), pp. 492-500 : 493-497

Papuamicrus gen. n.

Type species: Papuamicrus globosus sp. n. (here designated).

Diagnosis. Papuamicrus differs from all remaining members of the ‘ Cephennomicrus group’ in three unique apomorphies: (1) prosternal process in ventral view about as long as broad with concave posterior margin, so short that entirely situated on level of anterior margins of procoxae, which, in natural position, are separated by anterior tip of mesoventral process; (2) mesoventral and anterior metaventral processes fused into massive and broad (only ~3 times as long as broad) composite process with lateral margins slightly diverging posteriorly in posterior half, parallel in median and subapical regions, and anteriorly forming tricuspidate tip with strongly and rapidly narrowed anteriormost process fitting into posterior concavity of prosternal process; and (3) aedeagus with diaphragm shifted onto basal area, perpendicular in relation to long axis of median lobe, with median lentiform sclerotization forming attachment site for internal median longitudinal apophyse or tendon of intrinsic diaphragm retractor muscle. Moreover, the following combination of synapomorphies, separately occurring in other genera, but not all together, differentiates Papuamicrus from other genera of Cephenniini : (1) antenna with rapidly broadened, compact dimerous club; (2) head with frontal glands; (3) maxillary palpomere 4 button-shaped; (4) prothorax lacking internal sclerotized ‘reservoirs’ or cavities; (5) pronotum and elytra lacking pits and foveae; (6) procoxal cavities broadly closed posteriorly by postcoxal process of prosternum fused with postcoxal process of hypomeron; (7) prothoracic hypomeron not divided by transverse carina; (8) metaventral intermetacoxal process slightly narrower than mesoventral process, distance between metacoxae subequal to 1/6 of metaventral width at posterior metaventral margin; and (9) posterior margins of mesoventral rests non-carinate.

Description. Body ( Figs 1–3 ) suboval, strongly convex, virtually glabrous (but microscopic recumbent setae can be seen at high magnifications), pronotum and elytra lacking macrosetae.

Head capsule ( Figs 4–9 ) short and broad, in intact beetles strongly tilted downwards, so that plane of frons is perpendicular to coronal plane of body; frons and vertex confluent, together transverse; supraantennal tubercles small and weakly elevated; frons with pair of minute frontal glands ( Fig. 5 ; fg); eyes in male large, coarsely faceted, strongly convex and posteriorly emarginate, in female smaller and situated close to antennal fossae; gular plate (Fig. 0; gp) large, transverse, with sharply marked gular sutures ( Fig. 9 ; gs) and strongly transverse reticulate microsculpture, lacking large, oval punctures; posterior tentorial pits indiscernible; submentum short and strongly transverse, vestigial. Mentum ( Fig. 9 ; mn) rectangular, weakly transverse and slightly narrowing anterad, prelabium ( Fig. 9 ; plb) with six pairs of small suckers arranged in two longitudinal rows, labial palps minute and broadly separated, inserted at sides of prelabium, with palpomere 1 largest, slightly longer than broad, palpomere 2 slightly shorter and distinctly narrower than 1, slightly elongate, palpomere 3 much narrower and much longer than 2, rodlike with narrowed apex, about 3 × as long as broad. Maxillae generalized, maxillary palp ( Fig. 9 ; mxp) with minute palpomere 1, strongly elongate, slightly clavate palpomere 2, strongly broadened palpomere 3 which is less than twice as long as broad and has truncate apex, palpomere 4 broad and very short, button-like and densely setose. Mandibles ( Fig. 10 ; md) symmetrical, subtriangular, short, each with small dorsal mandibulo-labral interlocking projection, setose prostheca absent. Labrum ( Fig. 9 ; lbr) short and strongly transverse, with strongly rounded anterior margin, with membranous marginal velum and symmetrically distributed sparse dorsal setae.

Antennae ( Fig.10 )slender,composed of 11antennomeres,scape and pedicel distinctly broader than antennomeres 3–9, club dimerous, oval, abruptly delimited, more than twice as broad as antennomere 9. Antennomeres 1–9 sparsely setose, setae on club denser and longer than those on remaining portion of antenna.

Pronotum ( Figs 1, 3 ) in dorsal view broadly subtrapezoidal with lateral margins narrowing both posteriorly and anteriorly; anterior pronotal corners not visible in strictly dorsal view, blunt; posterior corners obtuse-angled and blunt; pronotal base lacking pits; lateral pronotal carinae smooth, not serrate, sharply developed on entire length.

Prosternum ( Fig. 9 ) with basisternal portion ( Fig. 9 ; bst) much shorter than coxal region; prosternal process ( Fig. 9 ; psp) in ventral view conspicuously short, not separating procoxae, about as long as broad and with concave posterior margin to receive anterior tip of mesoventral process, in lateral view only slightly elevated beyond ventral surface of procoxae; notosternal sutures ( Fig. 9 ; nss) complete; procoxal cavities broadly closed by posterolateral lobes of prosternum that are fused with postcoxal lobes of hypomera; hypomeral ridges diffuse and poorly discernible; hypomera ( Fig. 9 ; hy) broad and concave, lacking transverse carinae.

Mesoscutellar shield ( Fig. 1 ) partly exposed between elytral bases, broadly subtriangular, asetose and lacking pits.

Elytra ( Figs 1–3 ) oval, lacking humeral denticles and basal foveae; apices of elytra rounded together.

Mesoventrite ( Figs 2 , 11 ) with mesoventral intercoxal process ( Fig. 11 ; msvp) fused with anterior metaventral process and together forming elongate, nearly flat and broad platform between and behind mesocoxal rests; lateral margins of process slightly diverging posteriorly in posterior half, parallel in median and anterior regions, and anteriorly mesoventral process tricuspidate, with pair of small lateral subtriangular projections and abruptly narrowed subtriangular anterior tip fitting to posterior emargination of prosternal process. Mesoventral + anterior metaventral process with broad elevated lateral margins forming carinae tapering posteriorly.

Hind wings absent.

Metaventrite ( Figs 1 , 11 ) short and strongly transverse, distinctly narrowing posteriorly; posterior margins of mesocoxal rests not carinate; lateral margins weakly rounded, posterior margin sinuate along each metacoxa, with inversely subtrapezoidal metaventral intermetacoxal process ( Fig. 11 ; mtvp), as broad as 1/6 of metaventrite at posterior margin. Metanepisterna and metepimera narrow, partly exposed in intact beetles.

Legs ( Figs 2–3 ) moderately long and slender; pro- and mesocoxae oval, metacoxae strongly transverse; all trochanters short and subtriangular; all femora distinctly clavate; tibiae broadening distad; tarsi moderately slender.

Abdominal sternites ( Fig. 2 ) unmodified, first visible (III) slightly longer than each of IV–VII and subequal in width to last visible (VIII), abdomen subtriangular with broadly rounded apex, about as long as metaventrite.

Aedeagus ( Figs 12–15 ) strongly elongate, with symmetrical median lobe and asymmetrical endophallus with broadly tubular structures, diaphragm present, circular and conspicuously small, situated entirely on basal surface of aedeagus and bearing at center large lentiform sclerotization internally connected with median longitudinal apophyse that provides attachment for diaphragm retractor muscle; parameres slender, with apical setae, parameral base with small lateral lobes.

Distribution and composition. Papuamicrus is represented by one species known to occur in eastern New Guinea.

Etymology. The name Papuamicrus combines the prefix Papua - derived from the type locality, with the stem - micrus, often used in generic names for members of the ' Cephennomicrus group' of genera. Gender masculine.

Remarks. Papuamicrus shows a set of unique apomorphies (listed in diagnosis) not known in any other member of the ‘ Cephennomicrus group’ of genera within Cephenniini . These are ventral thoracic and aedeagal characters, difficult to observe. However, even in dorsal view, Papuamicrus can be easily identified by lack of pits and foveae on the pronotum and elytra, lack of conspicuously long and numerous macrosetae, and oval, compact, abruptly delimited dimerous antennal clubs. Within genera of the ‘ Cephennomicrus group’ which have a dimerous antennal club, it is usually loosely assembled, and not compact, not ‘histerid-like’. Exceptions are only Clavomicrus and Trurlia , but antennal clubs in these genera are composed of antennomeres 10 and 11 fused together, so that the antenna is composed of 10 separate antennomeres, and not 11, as in Papuamicrus . There is at least one, Trurlia -like and yet undescribed genus (mentioned in Jałoszyński (2011b)) with the antennal structure similar to that of Papuamicrus , but this genus seems to differ from Trurlia only in unfused two distal antennomeres, and its distinct dorsal foveal system, strongly elongate prosternal process fully separating procoxae, mesoventral process lacking anterior tip, and posteriorly carinate mesocoxal rests are clearly different from character states found in Papuamicrus .

Genera of Cephenniini (including the still unnamed ‘genus X1’ known from a single female collected in Sulawesi (characterized in Jałoszyński 2011b)) can be identified using the following key (see remarks in Jałoszyński (2020) for methods of observing some important characters):

Figures

FIGURES 1–4. Papuamicrus globosus gen. & sp. n. Habitus of male in dorsal (1), ventral (2) and lateral (3) views; head of male in lateral view (4).

FIGURES 5–11. Papuamicrus globosus gen. & sp. n. Head of male (5, 6) and female (7, 8) in anterodorsal (5, 7) and lateral (6, 8) views; head and prothorax in ventral view (9); left antenna in ventral view (10); pterothorax in ventral view (11). Abbreviations: bst, basisternal region of prosternum; cx1, procoxa; cx2, mesocoxa; cx3, metacoxa; fg, frontal gland; gp, gular plate; gs, gular suture; hy, hypomeron; lbr, labrum; md, mandible; mn, mentum; msvp, mesoventral intermesocoxal process; mtvp, metaventral intermetacoxal process; mxp, maxillary palp; nss, notosternal suture; plb, prelabium; psp, prosternal process; stIII, abdominal sternite III; v3, metaventrite.

FIGURES 12–15. Papuamicrus globosus gen. & sp. n. Aedeagus in ventral (12, 14) and lateral (13, 15) views.