Lapitachlaenius, Kipling & Will, 2025

Guéorguiev, Borislav & Will, Kipling, 2025, A new genus and tribal placement for Ceneus speculiferus Fairmaire, 1879, comments on Grundmannius Basilewsky, 1965, Mirachlaenius Facchini, 2011 and Stenoodes Basilewsky, 1953, and a key to the Oriental and Australasian genera of Chlaeniina Brullé, 1834 (Coleoptera, Carabidae), Zoosystema 47 (15), pp. 231-259 : 235-239

Lapitachlaenius n. gen.

urn:lsid:zoobank.org:act:7C063127-9D26-4B44-9D46-EEC43214085B

TYPE SPECIES. — Ceneus speculiferus Fairmaire, 1879: 70 , here designated.

DIAGNOSIS. — Integument of body glabrous throughout except for typical sensory setae (i.e., lacking pubescence as extensively evident in most Chlaenius s.l. species), concolorous often with a subtle aeneus or cupreous shade; surface of elytra immaculate. Pronotum and elytra smooth (without punctuation as in most Chlaenius s.l. species). Penultimate labial palpomere glabrous (also on inner margin), but with a minute seta near apex; ultimate labial palpomere fusiform in both sexes, not widened at apex, shorter than penultimate palpomere. Mentum tooth large, simple, widely rounded at apex. Antennomeres 1-3 and basal fifth to quarter of antennomere 4 glabrous; antennomere 3 just slightly longer than antennomere 4. Pronotum without anterolateral setiferous puncture, with posterior setiferous puncture about twice the width of fovea distant from posterior angle. Basal margin of elytra present, reaching base of stria 1 and/or base of parascutellar striole; parascutellar striole present, relatively long, punctiform (not linearly impressed as discal striae), reaching basal margin of elytra, not anastomosing with stria 1; interval 3 with four to seven foveate setiferous punctures; interval 8 interrupted subapically by a brief fusion of striae 7 and 8 ( Fig. 4 ), thus it is separated in two parts, long anterior and short posterior. Prosternal process unbordered. Metepisternum with sublateral longitudinal sulcus ( Fig. 3A, B ). Middle tibia straight in both sexes. Tarsomeres glabrous dorsally; male protarsomeres 1-3 more or less strongly dilated; tarsal claws simple, not pectinate (pectinate in species of Chlaenioctenus Bates, 1892 ; cf. Liu et al. 2013).

ETYMOLOGY. — The generic name is derived from the term “Lapita”, which is the name used for the Neolithic Austronesian culture that included the people thought to be the first settlers of the islands in the region, including Viti Levu, and the Greek noun “chlaena” [χλαῖνα] (cloak, mantle). The name is treated as a Latin masculine.

DESCRIPTION

Habitus

Medium sized for chlaeniines, with elongate, slightly convex body and glabrous integument.

Chaetotaxy

Labrum anterior margin with six dorsal equidistantly spaced setae as well with a row of shorter marginal lateral setae along each side and corner (each row continues ventrally at level of medial dorsal seta). Clypeus with two lateral punctures. One supraorbital seta on each side, located near posterior eye margin. Stipes with long dorsal seta; antennomere 2 with short ventral seta. Maxilla with two-segmented galea and pointed, highly bent at apex lacinia ( Fig. 2B ); apical margin of ligula with a pair of large and long medial setae and two groups of three or four, rather short and small, anterolateral setae ( Fig. 2C ). Penultimate labial palpomere glabrous, except for single minute apical seta; ultimate labial palpomere with sparse short setae visible only at higher magnification ( Fig. 1D ). Mentum with two long, paramedial setae. Submentum with two long, lateral setae. Pronotum with posterior lateral setiferous punctures, each puncture far removed from angle, distant by more than twice its diameter. Elytron with four to seven discal setiferous punctures in interval 3 near stria 2, (most apical one usually smaller and less perceptible than others); parascutellar seta present, at base of striae 1 and 2, puncture large, foveate, separated from basal margin by more than one of its diameters; apical portion of stria 7 with five to seven setiferous punctures (rarely a few of them on interval 7, not in stria), apical puncture closer to suture than to apex ( Fig. 4 ); umbilicate series consisting of 18-19 setiferous punctures of various sizes, not forming distinct groups. Mesocoxa with one posteromedial and one lateral seta; metacoxa with one lateral seta. Protrochanter and mesotrochanter with one seta. Metafemur without posterior setae. Abdominal ventrites 3-5 without ambulatory setae; last ventrite with two marginal setae in male and four setae in female. Gonocoxite 2 with one large dorsomedial seta, one lateromedial ensiform seta, and pair of nematiform setae.

Head

Eyes conspicuously large, protruding, with short tempora and dorsal diameter longer than combined length of antennomeres 1 and 2. Frons with small, punctiform, deepened frontal impressions. Mandibles relatively short, almost as long as wide, with outer margin evenly arcuate and strongly pointed incisor teeth; right mandible ( Fig. 2A ), with: 1) long retinacular ridge, however without anterior retinacular tooth and posterior retinacular tooth; 2) distinct terebral tooth; and 3) well-formed premolar and molar tooth; left mandible (not figured) of similar structure as right one, but with more prominent terebral tooth, distinct posterior retinacular tooth and respectively clear posterior occlusal groove between posterior retinaculum tooth and premolar. Maxillary palpomere 4 fusiform, slightly longer than palpomere 3, nearly as long as (but considerably narrower than) maxillary palpomere 2 ( Fig. 2B ). Ligula with glossal sclerite dilated anteriorly and slightly down directed, its apical margin straight in middle and bent at sides, paraglossae with lobes not extended distally beyond anterior margin of glossal sclerite. Mentum tooth simple, widely round at apex, with deep paramedial pits. Submentum narrow medially (and deeply concave at point of gular apical insertion), wider laterally. Gula widened posteriorly, separated from genae by distinct gular longitudinal sutures.

Thorax

Pronotum with sides widened, convexly rounded from anterior angles to point of maximum width then almost straight to posterior angles; maximum width just before middle; pronotum base with ( L. specularis n. comb.) or without ( L. speciluferus n. comb.) setal fringe along edge. Lateral bead distinct, narrow anteriorly, widened posteriorly, ended just at posterior angles. Anterior margin concave, submarginal bead laterally present, lacking in medial half; anterior angles very prominent, rounded at apex. Basal margin sinuate, slightly convex laterally, subconcave medially, without marginal bead, posterior angles obtuse and widely rounded. Disc with paramedial, parentheses-like, broad, shallow impressions that join with basolateral impressions; apical transverse impression present or not, if present shallow medially; basal transverse impression absent. Prosternum with median longitudinal sulcus shallowly impressed; prosternal process elongate-rhomboid, unbordered, pointed at apex. Mesosternum deeply concave. Metepisternum longer than wide, with deep sublateral sulcus along half to entire length, with lateral border slightly convex, coadunation with epipleuron located anteriorly and medially; suture between metepisternum and metepimeron distinct.

Elytra

Disc subconvex. Basal margin distinct laterally, forming at humerus obtuse angle with lateral margin, ended medially at level of angular base of stria 1 (i.e., at the level of parascutellar setiferous puncture).

Legs

Profemur in male with ( Fig. 1D ) or without ( Fig. 9 ) small, ventral tooth-like tubercle near base. Metacoxal basal sulcus short, ended at medial third. Mesotibial ctenidium (see Bousquet 1999: 13, 14) well-differentiated, consisting of 12-15 closely situated, subapical setae. Mesotarsomeres 1-3 and metatarsomeres in both sexes with 1-3 beneath with two rows of short and stout ventral setae and two rows of ventrolateral setae; onychium ventrally with one, rarely with two pairs of setae at apical half.

Female genitalia

See species description.

Male genitalia

See species description.

DISTRIBUTION AND DIVERSITY

The genus is endemic to the easternmost part of Melanesian Island arc and includes two species, one from the archipelago of Vanuatu and one from the archipelago of Fiji.

MONOPHYLY AND RELATIONSHIPS

At least four outstanding autapomorphies that are present in Lapitachlaenius n. gen., support the distinctiveness of the new genus. Three of them are features of the elytra, and one of the pronotum disc: 1) each elytron with a glistening, mirror-like area; 2) interval 3 with four to seven large, foveate setiferous punctures; 3) interval 8 distinctly interrupted into two portions along its length and 4) pronotum disc with broad and shallow paramedial, parentheses-like impressions that join with the baso-lateral impressions. These traits along with some other peculiar features (see Diagnosis), unusual among chlaeniine carabids, provide solid basis for recognition of the new genus.

We examined selected character states and their distribution among the species of Chlaeniina from the Australasian and Oceania regions ( Table 3 ) east of the Lydekker Line. This line demarcates the edge of the Sahul continental shelf and is used as an outermost boundary for delimitation of the typical Australasian fauna from the Oriental fauna ( Beron 2015). In total, 31 representatives of the subtribe Chlaeniina Brullé, 1834 have been reported to occur east of the Lydekker Line, 20 of them are microendemic species ( Table 3 ). These locally endemic species are known from: Micronesia, incl. Ogasawara Isl., Southern Mariana Isl. and Palau Isl. (5 species in Chlaenius ; cf. Darlington 1970a; Kasahara 1991; Mandl 1992), New Guinea with New Britain (13 species in Chlaenius and Hololeius ; cf. Sloane 1920; Darlington 1968; Azadbakhsh & Kirschenhofer 2019), Aru Islands (1 species of Chlaenius ; Häckel et al. 2023), Solomon Islands (5 species in Chlaenius ; cf. Emden 1937; Darlington 1968, 1970b), Australia (10 species of Chlaenius and Hololeius ; Sloane 1920; Moore 1987), Lord Howe Island (1 species in Chlaenius ; cf. Moore 1985, 1992), Norfolk Island (2 species in Chlaenius ; cf. Moore 1985), New Caledonia (4 species of Chlaenius , cf. Fauvel 1882; Chaudoir, 1883; Heller 1916; Sloane 1920; Darlington 1968; Kirschenhofer 2002, 2015), Vanuatu (3 species in Chlaenius and Lapitachlaenius n. gen.; cf. Emden 1937; Moore 1985), Fiji (4 species in Chlaenius and Lapitachlaenius n. gen.; cf. Darlington 1968; Evenhius 2007; present study), Samoa (2 species in Chlaenius ; cf. Csiki 1915; Andrewes 1927),Tahiti (1 species in Chlaenius ; cf. Darlington 1970a). No representative of the subtribe is known from New Zealand. Larochelle & Larivière (2001) stated that two Australian mainland Chlaenius species were introduced to Lord Howe and Norfolk Islands and that it is likely that will be discovered in New Zealand in time.

We found that the adults of Lapitachlaenius n. gen. share some specific features with the “ bimaculatus ” group of subgenus Lissauchenius W. S. MacLeay, 1825 . The last group includes four taxa in Australasia and Oceania – Chlaenius bimaculatus pongraczi Jedlička, 1951 , Ch. flaviguttatus (W. S. MacLeay, 1825) , Ch. olthofi Darlington, 1968 and Ch. rufifemoratus (W. S. MacLeay, 1825) as first and third taxa are endemics in New Guinea ( Table 3 ). Species of “ bimaculatus ” group and species of Lapitachlaenius n. gen. share: antennomere 3 not or only slightly longer than antennomere 4; mandibles relatively short, as long as wide, moderately arcuate towards tips ( Fig. 2A ); abdomen largely smooth and glabrous medially; male front femur with a small tooth-like tubercle below ( Fig. 1D ) (character presumed to have been secondarily lost in L. specularis n. comb.). For more on the distribution of the enumerated characters in some taxa of the “ bimaculatus ” group see Darlington’s (1968) “Key to species of Chlaenius of New Guinea ”. It is assumed that the six species noted above share the state of having a simple mentum tooth that is rounded at apex. Among the taxa of “ bimaculatus ” group the simple mentum tooth is only documented in Ch. olthofi (Darlington ibid.).

A plausible hypothesis of the evolution of the genus is that there was a single, eastward, long-distance dispersal event (Gillesbie et al. 2012), perhaps in the Early Miocene (or during an earlier geological epoch), of a common ancestor of Lapitachlaenius n. gen. and the “ bimaculatus ” group of Lissauchenius . Presumably, after the colonization event the lineage experienced remarkable modifications in terms of the pronotum relief, elytral relief, and elytral setiferous setation, all well before both the Fiji-Vanuatu split ( Martin 2013) and then subsequently underwent species-level differentiation.

Formation of the two species is potentially a relatively recent event. It is likely the result of the separation of a widespread, ancestral population in the course of the breakup of the formerly continuous Vityaz Arc that separated into the Vanuatu and Fijian land masses, with the North Fiji Basin opening between them during the subduction processes in the Miocene ( Martin 2013; Gill et al. 2022). The breakup of this arc acted as a significant vicariance event and driver for speciation in various groups ( Liebherr 2005; Ferguson et al. 2023; Saxton et al. 2023).

Figures

FIG. 4. — Lapitachlaenius speculiferus (Fairmaire, 1879) n. comb., male specimen, apical portion of stria 7 of left elytron. The left arrow indicates the interruption of interval 7, whereas the right arrow points to the terminal setiferous puncture in stria 7. Scale bar: 0.5 mm.

FIG. 3. — Lapitachlaenius speculiferus (Fairmaire, 1879) n. comb., male specimen: A, left metepisternum. Arrows mark a depression on medial margin of elytral epipleuron that usually is covered by a lateral protrusion of metepisternum – edge of the protrusion is marked by a continuous red line; B, right metepisternum. Arrow points to the sublateral longitudinal sulcus of metepisternum. Scale bars: 0.5 mm.

FIG. 2. — Lapitachlaenius speculiferus (Fairmaire, 1879) n. comb., female specimen, mouthparts: A, right mandible, dorsal view; B, right maxilla, ventral view; C, glossal sclerite,dorsal view. Abbreviations:car, cardo;dls, dorsal lobe of stipes;g1, galeomere 1; g2, galeomere 2; gsc, glossal sclerite;it, incisor tooth; lc, lacinia;lgs, lateral glossal seta;mgs, medial glossal seta;lp2, labial palpomere 2;mp1-4, maxillary palpomeres 1-4; mt, molar tooth;pgl, paraglossa;pog, posterior occlusal groove; pmt, premolar tooth; rr, retinaculum ridge; tr, terebral ridge; tt, terebral tooth; vls, ventral lobe of stipes. Scale bars: A, C, 0.2 mm; B, 0.5 mm.

FIG. 1. — Lapitachlaenius speculiferus (Fairmaire, 1879) n. comb., male specimen: A, dorsal view; B, left lateral view; C, head and pronotum; D, head and fore right leg, ventral view. The white arrow points to the profemur ventral tooth-like tubercle. Scale bars: A, B, 2 mm; C, D, 1 mm.

FIG. 9. — Lapitachlaenius specularis (Emden, 1937) n. comb., male paratype, prothorax and fore right leg,ventral view.The white arrow points to the absence of profemur ventral tooth-like tubercle. Scale bar: 1 mm.