Distinguishing Bolboceras inaequale Westwood, 1848 and two new relatives from India (Coleoptera, Geotrupidae, Bolboceratinae)

Abstract The taxonomy of the Bolboceras inaequale group of species is discussed. The group as here conceived comprises three species in the Indian subcontinent: Bolboceras inaequale Westwood, 1848 (reputedly also ranging into sub-Saharan Africa), and two new species: Bolboceras duplicatum, and Bolboceras orissicum, both from India. All three are keyed, diagnosed, and illustrated; variability and potential taxonomic obstacles are briefly discussed.


Introduction
Within the mainly South Asian genus Bolboceras Kirby, 1819(nomenclature, cf. ICZN 2006 various operational groups of species can be recognized (Krikken in press). One is the Bolboceras inaequale group, comprising a few species with -at least in major individuals -a characteristic set of three pronotal concavities behind and between a transversely arranged double pair of antediscal tubercles (two discoparamedian and two discolateral tubercles, terminology by Krikken (in press)); the discomedian impression is enclosed all around (basin-like), and characteristically shaped in major individuals. The single named species in the group, Bolboceras inaequale Westwood, 1848, has been recorded from both the Indian subcontinent and northern sub-Saharan Africa. This paper is intended to show that there is more to the inaequale group than this single described species, by discussing the diversity among South Asian group members, while focusing on the identification of two new relatives from India. It is very likely that in the future, based on informative series from more localities, additional taxa will be recognized, while any minor individuals can then be interpreted better than is currently the case; the identity of sub-Saharan material referred to B. inaequale (by Paulian 1941) may also be clarified in the process.
Comparisons of the aedeagi are, as usual in Bolboceratinae, important, but the principle is: externally different aedeagal shapes indicate potentially different species, similar shapes do not necessarily indicate a single particular species. The basic structure and terminology of the aedeagus in Bolboceras is illustrated in Krikken (in press).
The inaequale operational group is defined below, the second paragraph including the broader generic Bolboceras features as applicable to the Asian species.

Material and methods
For more information on Bolboceras, its nomenclature, subdivision into groups, related genera, and technical conventions, cf. Krikken (2013). The list of material examined under B. inaequale follows the original label texts. Specimens and body parts are pictured as is -no remounting, to prevent damage.

Collections
The material on which this study is based comes from the collections listed hereafter. I most gratefully acknowledge the patient collaboration of the staff concerned.

The Bolboceras inaequale group
Group characters. Upright conical-triangular discoparamedian tubercles on pronotum distinct, more or less approximated, connected by variably wide transverse saddle (watch out for minor morphs); major specimens with broad, well defined discomedian concavity situated (largely) behind these tubercles (shape of its posterior edge varying, arcuate to W-shaped) -minor specimens with similar, more superficial ornamentation; discomedian concavity on either side separated from discolateral concavity by variably elevated saddle (connecting discoparamedian tubercles to posterior disc). Outline of clypeus subtrapeziform (i.e. oblique lateral perimarginal ridges running to anterolateral angles of main surface on either side of transverse anterior ridge, not converging to a single anteromedian tubercle); clypeal surface inside perimarginal ridges without protrusion(s).
Total 47 males and females, 33 collection records, and Westwood's material. Diagnosis. Ridge (or saddle) separating discomedian and discolateral concavities on pronotum narrow, lowered in relation to surrounding discal surface; discoparamedian tubercles approximated (connected by saddle), their tip subacute; discolateral concavity in major males extending down, onto anterolateral surface. Posterior edge of discomedian concavity usually distinctly W-shaped in major individuals, in minors the pronotal ornamentation may be only just distinct (in oblique view); bottom of concavities more or less sericeous. Interocular ridge low, not reaching paraocular ridge on either side, situated between posterior part of eyes. Anterolateral corners of clypeus usually protuberant (in majors intervening ridge concave in axial view). Scutellum usually closely punctate. Intermesocoxal lobe of metasternum anteriorly with arcuate ridge. Aedeagus (Fig. 13) with acuminate parameres, median apparatus with pair of strongly sclerotized lateral stalks, their tip broad, shortly recurved-hooked. Colour uniformly brown. Body length usually 11-13, some series down to ca 9 mm or less (see next section).
Variation. There are small individuals (minors) from Northeast India and Bangladesh (a male from Dhanjuri in Bangladesh pictured here, ca 9 mm long, Figs 3-4, 10, 18-19), characterized by a minimal set of pronotal protrusions and impressions, but still with distinct traces of the basic pattern -and also with a smaller, but externally quite similar aedeagus. Some intermediates between these minors and the real majors (including the type) were seen. At this moment I find no morphological support for ranking the minors as a separate taxon -informative material from different locations required. Paulian (1941) mentions a length range for B. inaequale of 7-12 mm.
"W" (meaning Westwood's original collection), one of them with this label only. The specimen here qualified as syntype has a curatorial label of the 1960s, indicating its registration as Coleoptera type 516, plus additional post-Westwood labels. The three specimens are considered conspecific, and consequently, at this moment, an explicit lectotype designation appears unnecessary.
Distribution. India (southern occurrences to be confirmed), Bangladesh; northern sub-Saharan Africa (needs confirmation). Diagnosis. Saddle separating discomedian from discolateral concavities on pronotum short, thick, slightly lowered in relation to surrounding surface; discoparamedian tubercles approximated, but less than in the preceding species; discolateral concavity in no way extending onto anterolateral pronotal declivity. Interocular transverse ridge low, reaching paraocular ridge on either side, about halfway eye. Posterior edge of discomedian concavity only vaguely W-shaped. Pronotal tubercles with rounded tip. Anterolateral corners of clypeus appearing not strongly protuberant. Scutellum sparsely, finely punctate. Aedeagus unusual for Bolboceras: with blunt, membraneous parameres, the median apparatus lacking projecting sclerotized lateral stalks. Colour uniformly medium-brown. Body relatively large (length assumed roughly 10-11 mm).
Intercoxal anterior lobe of metasternum simply truncate in front. Protibia with 6 external denticles (tips worn off); apex unmodified, with robust, complanate, slightly tapering spur. Outher side of meso-and metatibiae with bilobate apical and one complete anteapical fossorial elevation (their crest fringed with fine spines).
Measurements of body parts. Median length of head (full-face, excluding labrum and mandibles) 2.5 mm, width 3.6 mm. Median length of pronotum (dorsal) 4.2 mm, maximum width 7.1 mm. Median length of scutellum 1.2 mm, maximum width 1.4 mm. Sutural length of elytra (dorsal) 4.1 mm, maximum width combined 7.2 mm. Width of genital capsule 1.20 mm.
Variation. Only one male seen -beware of possibly deceptive polymorphism. Distribution. Southeast India. Etymology. Name refers to its similarity to the preceding species. Diagnosis. Saddle separating discomedian and discolateral concavities on pronotum very short, broad, not lowered in relation to surrounding discal surface, discoparamedian tubercles distinctly separated by anterior part of discomedian concavity between them; discolateral concavity quasi-extending onto shallowly concave anterolateral corner; posterior edge of discolateral concavity well defined, "swollen" near saddle with discomedian concavity (outline in dorsal view sinuate). Posterior edge of discomedian concavity virtually rounded. Interocular transverse ridge situated between posterior part of eyes, low, not reaching paraocular ridge on either side. Anterolateral corners of clypeus strongly protuberant (intervening ridge concave in axial view). Scutellum usually abundantly punctate. Aedeagus with narrow, acuminate parameres, median apparatus with pair of strongly sclerotized lateral stalks, their tip very broadly recurved-hooked. Colour uniformly light-brown. Body length roughly 12.5-13.5 mm.
Labrum with emarginate anteromedian border, transverse ridge on rugulate upper surface fine, distinct. Clypeal surface with supra-anterolateral angles distinctly raised, dentate, intervening ridge concave in axial view, straight in full-face view; lateral perimarginal ridges distinct, strongly evenly curved, genal angle distinct. Clypeus densely punctate, remainder of head surface abundantly, evenly, distinctly punctate, primary punctures interspersed with fine secondary punctation being denser behind interocular ridge. Anterior edge of eye canthus raised to slight anterolateral angle, thence arcuate along edge of distal lobe; surface coarsely rugulate; paraocular ridge distinct, fine issuing from genal angle, virtually straight, extending posteriorly along eye. Transverse interocular elevation between posterior part of eyes, long, low, not reaching paraocular ridges, lateral slope slight, crest fine, unmodified, lateral angle obtuse on either end (axial view). Much of head surface subsericeous.
Protibia with 6 external denticles; apex unmodified, with robust, complanate, slightly tapering spur. Outer side of meso-and metatibiae with bilobate apical and one complete anteapical fossorial elevation (their crest fringed with fine spines).
Variation. Variation slight, but beware of possibly deceptive polymorphism (may be obvious in larger series).
Sexual dimorphism. No obvious sexual dimorphism. Distribution. Northeast India, apparently South of the Ganges. Comment. The place called Burju, origin of the paratypes, is mentioned in the list of "post-office pincodes" in the Ranchi District of Jharkhand (India), and at the time of the collection of the SMF specimens there was a German mission school in the area, with staff sending specimens to German entomologists (around 1890-1910).
Etymology. Named after the type region.