The South American endemic dung beetle genus Ennearabdus Lansberge is revised. Description, diagnosis and illustrations are presented for the only known species of the genus, E. lobocephalus (Harold). A lectotype is designated for Onthophagus lobocephalus Harold, the type species of Ennearabdus. The biology, biogeography, conservation status, and distribution based on the predictive distribution model of E. lobocephalus are also discussed.
The genus Ennearabdus Lansberge is a monotypic endemic of the Argentinean North Western region that is rarely collected (probably because the area is not frequently visited by entomologists) and is consequently rare in collections. This genus is a member of the tribe Eucraniini, a relatively small tribe of dung beetles currently with four genera that is endemic to Argentina. The systematic placement of the genus within dung beetle classifications has been enigmatic and has changed numerous times. The only known species, E. lobocephalus (Harold 1868), was originally placed in the genus Onthophagus Latreille (Onthophagini). Later, Lansberge (1874), described the genus Ennearabdus and indicated that the genus was related to the Phanaeini as a “transition form” between them and the “Coprides”(i.e, Copris Geoffrey, Dichotomius Hope). Since Lansberge (1874), the genus was placed in catalogs as a Phanaeini (Gillet 1911; Bruch 1911; Blackwelder 1944). Olsoufieff (1924) did not treat the genus in his revision of Phanaeini. Later, Pereira and Martinez (1956) considered that there was not enough justification to keep Ennearabdus in Phanaeini and described the tribe Ennearabdini for this monotypic genus, but they did not indicate its phylogenetic relationships. Zunino (1983, 1985) was the first author to indicate the relationship between Ennearabdus and the tribe Eucraniini, at that time composed of three genera, Eucranium Brullé, Anomiopsoides Blackwelder, and Glyphoderus Westwood. Philips et al. (2002) and Ocampo and Hawks (2006), in their phylogenetic analysis based on morphological and molecular data, respectively, proposed a close relationship of the four Eucraniini genera and its sister group, the Phanaeini. Zunino et al. (1993), Monteresino and Zunino (2003), and Ocampo and Hawks (2006) described various aspects of the biology and behavior of E. lobocephalus.
The purpose of this contribution is to provide a taxonomic revision of Ennearabdus, and discuss this species' biology, biogeography, and conservation status.
Material and Methods
Body measurements, puncture density, puncture size, fovea density, fovea size, and density of setae are based on the following standards. Body length was measured from the apex of the pronotum (at the middle) to the apex of the elytra, head is excluded and measured separately because the variable position of the head and length of clypeal teeth render it impractical to include in the body length). Body width was measured across mid-pronotum. Puncture density was considered “dense” if punctures were nearly confluent to less than two puncture diameters apart, “moderately densely foveate” if punctures were two to six diameters apart, and “sparse” if punctures were separated by more than six diameters apart. Puncture size was defined as “small” if punctures were < 0.02 mm in diameter, “moderate” if 0.02–0.07 mm in diameter, and “large” if > 0.07 mm in diameter. Surface was defined as “sparsely foveate” if there was (on average) a space of more than one diameter between foveae, “moderately dense” if there were 0.5–1.0 diameters between foveae, and “densely foveate” if foveae were confluent or separated by less than 0.5 diameters. Setae were defined as “sparse” if there were few setae and surface is distinctively visible, “moderately dense” if the surface was visible but with many setae, and “dense” if the surface was not visible through the setae. Elytral carinae were counted from the elytral suture. Specimen labels were copied literally using a “/” between lines.
Lectoypes are here designated to provide the nomenclatural stability of the taxon studied, according to Article 72 of the International Code of Zoological Nomenclature.
Specimens for this research were collected, borrowed from and deposited in the following institutions and collections.
CMNC: Canadian Museum of Nature, Ottawa, Canada (RS Anderson, F. Génier).
IAZA: Instituto Argentino de Investigaciones de las Zonas Áridas, Mendoza, Argentina (S Roig-Juñent, FC Ocampo).
MNHN: Muséum National d'Histoire Naturelle, Paris, France (O Montreuil).
UNSM: University of Nebraska State Museum, Lincoln, NE, USA (BC Ratcliffe, ML Jameson-Russell).
USNM: United States National Museum, Washington D.C. USA (D Furth).
Predictive models of species distribution
Species distribution models are used to predict species potential distribution by relating known species collection localities to a set of environmental variables that, presumably, reflect the ecological niche of the species (Guisan and Thuillier 2005). Known localities for E. lobocephalus were georeferenced and mapped to model its distribution using predictive methods based on bioclimatic variables. MaxEnt (Phillips et al. 2006) was used combined with 19 bioclimatic variables obtained from WorldClim dataset (Hijmans et al. 2005). The resolution of the environmental layers was approximately 4.6 × 4.6 km.
Type species: Onthophagus lobocephalus Harold 1868: 84, by monotypy.
Lectotypes. Lectotype at MNHN labeled: “Mendoza;” “lobocephalus / Harold;” “Ex. Musæo / E. Harold;” “Muséum Paris / ex coll / R. Oberthür / 1952;” “Ennearabdus lobocephalus / det: F. C. Ocampo / ID: FCO5062;” “Onthophagus lobocephalus / Harold / Lectotype / F. Ocampo det.” (red label, handwritten).
Paratypes. One paralectotype at MNHN with same label as lectotype except: “Ennearabdus lobocephalus / det: F. C. Ocampo / ID: FCO5063;” “Onthophagus lobocephalus / Paralectotype / F. Ocampo det.” (yellow label, handwritten). One paralectotype at IADIZA labeled: “Mendoza / lobocephalus / Har.;” Museum Paris / coll. H. W. Bates / 1952;” “Museum Paris / ex coll. / R. Oberthür / 1952;” “Ennearabdus lobocephalus / det: F. C. Ocampo / ID: FCO5064;” “Onthophagus lobocephalus / Paralectotype / F. Ocampo det.” (yellow label, handwritten). Four paralectotypes at MHNH and one at IADIZA labeled: “Ex. Musæu / E. Harold”; “Museum Paris / ex coll. / R. Oberthür / 1952;” “Ennearabdus lobocephalus / det: F. C. Ocampo / ID: FCO5065” (and sequential numbers: FCO5066–69). “Onthophagus lobocephalus / Paralectotype / F. Ocampo det.” (yellow label, handwritten). One paralectotype at MNHN labeled: “Ex. Musæu / E. Harold;” “Museum Paris / ex coll. / R. Oberthür / 1952;” “Ennearabdus lobocephalus / det: F. C. Ocampo / ID: FCO5070;” “Onthophagus lobocephalus / Paralectotype / F. Ocampo det.” (yellow label, handwritten).
Diagnosis. Ennearabdus lobocephalus can be recognized from other members of the tribe by the hind wings fully developed (obsolete in the other genera), the metasternum relatively wide between mesocoxae (narrow in the other genera); and meso- and metatarsi with tarsal claws present, although reduced (tarsal claws absent in the other genera). The genus Ennearabdus can be recognized from the Phanaeini genera, to which Eucraniini is the sister taxon, by the meso- and metatibiae slender, expanded at apex and the meso- and metatarsal claws developed. The genus Ennearabdus can be recognized from South American Dichotomiini genera by the meso-and metatibiae slender, the metasterno gibbose, and the protarsi not developed.
Redescription. Male. Body length 7.56–10.80 mm, width 6.13–8.78 mm, head length 3.37–4.19 mm. (n = 78). Color: head, pronotum and elytra dull to shiny black, rarely with metallic green reflections; venter shiny black. Head (Figures 1, 2, 9): Frons convex, surface punctate at apex to rugopunctate at base. Paraocular area slightly convex, surface densely punctate, with small, reflexed tooth at apex. Postocular lobes of parietal depressed transversely (Figure 2). Cephalic carinae well developed, with 2 simple horns, horns variable in length (Figures 1, 9). Eyes small, completely divided, dorsal and ventral half not dorso-ventrally aligned. Canthal area distinct, slightly concave (Figure 2). Clypeus transverse; surface densely rugose (net-like), punctures large, clypeal anterior border smooth, with fringe of short setae, quadridentate, reflexed; me