Rhytisternus externus, Baehr & Reid, 2017

Baehr, Martin & Reid, Chris A. M., 2017, On a Collection of Carabidae from Timor Leste, with Descriptions of Nine New Species (Insecta: Coleoptera, Carabidae), Records of the Australian Museum 69 (6), pp. 421-450: 428-429

publication ID

http://doi.org/ 10.3853/j.2201-4349.69.2017.1660

publication LSID

lsid:zoobank.org:pub:0622726F-CAC8-4816-B6B7-2DF2E8BDDA50

persistent identifier

http://treatment.plazi.org/id/D1658794-EF63-FF84-BBAE-FF37FBB6FA88

treatment provided by

Felipe

scientific name

Rhytisternus externus
status

sp. nov.

Rhytisternus externus   sp. nov. Baehr

Figs 3 View Figure 3 , 13 View Figure 13 , 19 View Figures 18–22

Holotype ♂, “ TIMOR LESTE Ramelau 8°54'45"S 125°29'58"E stunted eucs/ Vaccinium   /open grass 2450– 2550m 28.v.2012 C.Reid TL2012/091/576” K402537 ( AMS) GoogleMaps   . Paratypes (13): 1♀, same data, K402536 ( AMS) GoogleMaps   ; 7♂♂, 3♀♀, “ TIMOR LESTE Ramelau sum’t plat. 8°54'51"S 125°39'31"E 28.v.2012 stunted eucs/ Vaccinium   /moss/grass 2750m C. Reid grass tufting TL2012/090/575” K402526– 528, K402530–531, K402533–535 (6♂♂, 2♀♀, AMS) GoogleMaps   ; 1♂, 1♀ K402529, K402532 ( CBM)   ; 1♀, “ TIMOR LESTE Ramelau 8°54'28"S 125°30'10"E stunted eucs/ Vaccinium   / gully 2300–2400m 28.v.2012 C. Reid TL2012/092/582” K402538 ( AMS) GoogleMaps   ; 1♀, “ TIMOR LESTE nr Desa Liurai , Hatubuilico rd, 2.5k W t’off highwaY 8°52'41"S 125°34'36"E Euc. urophylla   /grass/vacc woodland 24–28.v.2012 [pitfall trap] 1850m J.Recsei TL2012/079/511” K402539 ( AMS) GoogleMaps   .

Etymology. The name refers to the occurrence of this species outside Australia.

Diagnosis. Moderately large species (in genus), distinguished from the Australian species by the narrow, elongate, slightly ovoid, and dorsally convex elytra, and by the reduction of the posterior wings, also from most species by the complete striation of the elytra.

Description. Measurements. Body length: 10.8–12.1 mm; width: 3.65–4.1 mm. Ratios. Width/length of pronotum: 1.16–1.25; width of widest diameter/base of pronotum: 1.29–1.35; width base/apex of pronotum: 0.96–1.0; length/ width of elytra: 1.76–1.83.

Colour ( Fig. 3 View Figure 3 ). Dark piceous to black, in some specimens scutellum and suture inconspicuously reddish-brown. Labrum and mandibles dark red, palpi and antenna red, apical antennomeres slightly paler. Legs dark red, femora in parts darker. Lower surface very dark piceous to black, but epipleurae of prothorax and of elytra, and the apical margin of the terminal abdominal sternum dark red.

Head ( Fig. 3 View Figure 3 ). Narrower than pronotum, dorsally slightly convex. Eye moderately large, laterally little projected, orbit elongate, oblique, more than half as long as the eye. Labrum slightly excised at apex   . Mandibles of normal size and shape, near apex incurved. Mentum with a bifid mental tooth, with two elongate setae; submentum also with two very elongate setae. Labium apically widened, bisetose. Palpi of normal size and shape, impilose. Antenna rather short, median antennomeres c. 1.5 × as long as wide, antenna pilose from 4th antennomere. Frontal furrows deep, linear, sinuate, attaining level of anterior third of the eye, ending abruptly. Frons slightly convex, neck with a weak neck constriction. The posterior supraorbital seta inserted slightly posteriad of the eye. Surface with dense but verY punctures and onlY verY superficial traces of verY fine, about isodiametric microreticulation.

Pronotum ( Fig. 3 View Figure 3 ). Slightly wider than long, somewhat cordiform, base as wide as, or slightly narrower than apex; disk dorsally slightly convex. Pronotum widest at, or slightly in front of middle. Apex barely excised, apical angle very slightly projected, but widely rounded. Lateral border evenly convex to base, without any perceptible prebasal sinuation. Base laterally slightly oblique. Basal angle obtusely angulate, c. 110°. Lateral margin narrow throughout. Both, apex and base not margined. Median line deeply impressed, not attaining the apex, but almost attaining the base. Both transverse impressions wide and shallow. Basal grooves deep, linear, almost straight, extended to the basal third of the pronotum. The anterior lateral seta inserted slightly behind the apical fourth of the pronotum, the posterior seta located on the basal angle. Disk in middle with short, extremelY superficial transverse strioles, with extremelY fine, barelY perceptible punctures, and verY fine, though distinct, isodiametric microreticulation. Surface but moderately glossy.

Elytra ( Fig. 3 View Figure 3 ). Narrow and elongate, somewhat ovoid, widened posteriad, widest about at apical third. Dorsal surface moderately convex. Humeral area comparatively narrow, lateral margin in basal half straight but oblique, in apical half evenly convex, but deeply sinuate where the epipleura is crossing the margin. Humerus obtuse or obtusely convex. Apical part convex and slightly incurved towards the suture. All striae distinct and complete, well impressed from base to apex, barely crenulate; intervals distinctly raised, slightly convex. Scutellary striole absent, scutellary puncture and seta present, situated at base of 2nd stria. 3rd interval impunctate. Marginal series composed of 15 punctures which are widely interrupted in middle. At apex   of 7th and of 2nd striae with an additional puncture and seta. Intervals impunctate, with verY fine though distinct, isodiametric microreticulation; surface but moderately glossy. Metathoracic wings short.

Lower surface. Prosternal process not margined and asetose. Proepisternum with several distinct, transverse sulci, in dorsal part finelY punctate. Mesepisternum coarselY punctate. Metepisternum rather short, c. 1.25 × as long as wide at apex   , almost impunctate. Abdominal sterna laterally punctuate, but punctures posteriad increasinglY finer. Whole abdomen with verY fine, isodiametric microreticulation. Terminal sternum in male bisetose, in female quadrisetose.

Legs. Of normal size and shape. 5th tarsomeres with 2–3 elongate setae on either side of the lower surface. 1st–3rd tarsomeres of male protarsus biseriately squamose underneath.

Male genitalia ( Fig.13 View Figure 13 ). Genital ring convex, with asymmetric, oblique-convex apex. Aedeagus strongly sclerotized, rather narrow and elongate, about straight, lower surface very concave. Apical part depressed, asymmetric, subapically on the right side deeply concave, at tip irregularly oblique. In apical fifth on the left side dorsallY with a denticle that is directed upwards and posteriad, also near the very apex the upper surface on the left side slightlY raised. Orificium elongate, situated on the upper surface but slightly moved right. Internal sac without any sclerotized parts, very simply folded. Left paramere short and wide, about quadrangular, at apex   almost perpendicular, but at bottom of apwx with a short, little sclerotized protuberance. Right paramere narrow, somewhat axe-shaped, with elongate, regularly narrowed apex.

Female gonocoxites ( Fig. 19 View Figures 18–22 ). Gonocoxite 1 elongate, without setae at the apical rim of the ventral surface; gonocoxite 2 curved, with obtusely angulate apex, with one elongate dorso-median ensiform seta below middle, four elongate, rather stout ventro-lateral ensiform setae in the basal half, and two fairly elongate, preapical nematiform setae originating from a large pit. Lateral plate mediad at apex   with a few rather stout setae.

Variation. No significant variation noted.

Distribution. Western part of Timor Leste, where it is confined to the highest Timorese mountain (Ramelau) and associated ridges.

Collecting circumstances. Sampled at high altitudes (1850–2750 m) in stunted or tall eucalypt woodland with Vaccinium   , grass and moss.

Relationships. The new species is tentatively attributed to the Australian genus Rhytisternus   due to several diagnostic characters, for example, the transverse striolation of the proepisternum, absence of the scutellary stria and of the discal punctures on the elytra, and absence of transverse sulci on the abdominal sterna. Also the male genitalia, aedeagus, parameres, and genital ring, in shape and structure are very similar to those of some Australian species that have been dissected for comparison. However, in body shape, the complete striation of the elytra, and the reduction of the metathoracic wings the species deviates from all described Australian species. Because the genus Rhytisternus   has not been revised in recent times, the relationships of the new species from Timor with those from Australia presently remain somewhat doubtful.

Remarks. The discovery in Timor of a new species of the Australian genus Rhytisternus   , or at least of a species closely related to that genus, is not too surprising and corroborates the close relationship of the Carabid fauna of Timor to that of northern Australia. It is already known that species of otherwise Australian carabid genera occur outside that continent on New Guinea or on islands in the southern part of the Indonesian Archipelago, for example, on Sulawesi, the southern Lesser Sunda Islands, the Moluccas, Aru, Kei, and Tenimber Islands.

However, the habits of the new species are quite different from those of the Australian species of Rhytisternus   , as far as they have been recorded, because the species from Timor, in contrast to all Australian species, apparently is not decidedly hygrophilous. On the contrary, it has been sampled not only at high altitude, but, even more important, in open eucalypt woodland with grass, and not in the vicinity of open water or of wetlands. The montane habits may have caused the reduction of the flYing abilitY, because wing reduction is very common in montane species, for example, in the New Guinean species of Rhytiferonia   ( Darlington, 1962; Baehr, 2001b).

Darlington (1962) discussed the possible relationship of the New Guinean genus Rhytiferonia   with the Australian Rhytisternus   , but denied any close relationships due to the quite different bodY shape, presence of a transverse sulcus on the abdominal sterna in Rhytiferonia   , and absence of the scutellary puncture and seta in the New Guinean genus. Presence, or absence, of transversely sulcate abdominal sterna is usually considered phylogenetically important, which per se would render close relationship unlikely. But also body shape and habits of the species of Rhytiferonia   are quite different from those of all species of Rhytisternus   , because the New Guinean species are bulky, possess reduced wings and no flYing abilitY, and inhabit open woodland and subalpine meadows at high to very high altitude.

The new species from Timor, although agreeing in almost all constitutive character states with Rhytisternus   , in its montane habits and the loss of flYing abilitY agrees with the New Guinean species of Rhytiferonia   . Therefore, it may be another, independent descendent from a common origin which is apomorphic, as compared with the species of Rhytisternus   , in its montane way of life and its loss of abilitY for flight. There are not enough differences to exclude it from Rhytisternus   .

CBM

Natural History Museum and Institute