Onthophagus basicarinatus, Rossini & Vaz-de-Mello & Zunino, 2018

Rossini, Michele, Vaz-de-Mello, Fernando Z. & Zunino, Mario, 2018, A taxonomic revision of the New World Onthophagus Latreille, 1802 (Coleoptera: Scarabaeidae: Scarabaeinae) of the osculatii species-complex, with description of two new species from South America, Journal of Natural History 52 (9 - 10), pp. 541-586 : 566-568

Onthophagus basicarinatus sp. nov.

( Figures 2 (e – g), 2(m – q), 5(b))

Diagnosis

Males of O. basicarinatus are easily recognized by the frontal horns carinated at the base ( Figure 2 (g)), clypeus triangular and truncated at middle. The anteromedial pronotal protuberance of male is triangular and very narrow between the cephalic horns. The female has two cephalic carinae, the frontal carina is entire and straight at middle, the clypeus is triangular and distinctly narrower towards the apex, the pronotal disc is strongly and densely punctated (separated by less than one diameter).

Description

Body length 6 – 8 mm. Colour. Body reddish-brown to dark brown and shining, sides of pronotum, and humeral umbones paler, ventral side of the body brownish, pygidium, last abdominal sternite, middle-, metafemurs, scape, antennal articles I – V and mouthparts brownish-orange, antennal club orange-yellow. Head. Clypeus triangular and elongated forward, clypeal margin narrowly and transversally truncated at middle and slightly reflexed, head margin barely sinuated at the clypeo-genal junction. Fronto-clypeal region without carina, frons with two strong horns, slightly and evenly curved inward, internobasal side of the horns strongly expanded and carinate ( Figure 2 (g)). Clypeus very finely punctated, fronto-clypeal region and frons with deeper punctures. Thorax. Pronotum with lateral margins evenly curved, anterior angles acuminated, anterior and lateral margins bordered, posterior margin with border evanescent near posterior angles. Anteromedial pronotal protuberance narrowly rounded between cephalic horns (almost triangular-shaped), protuberance flanked by two wide concavities, superior side of protuberance flattened to slightly depressed. Pronotal surface densely and evenly punctated, punctures shallow and with a central pit, main punctation mixed with secondary punctures, anterior angles simply punctated, posteromedial region of pronotum widely sulcate, sulcus long (sometimes reaches the anterior protuberance), depressed region finely microreticulated and shallowly punctated. Elytral striae shallow, stria VII slightly more impressed near the base, interstriae flat and finely microreticulated, punctation dense, sparse and shallow, interstria VII and base of interstria VI with setiferous punctures, setae very short, straight and yellow, scattered setae even at the apex of elytra. Propleuron with a very small and triangular tubercle in proximity of the anterior angles of pronotum (visible at high magnitude, 40× – 50×), propleural carina thin and sinuated near external margin, setiferous and asperous punctures in front of the propleural carina, setiferous and coarse punctures along the external margin of propleuron, setae long and straight. Prosternum distinctly and obtusely acuminated at middle, with short and straight setae, mesosternal surface crowded with setiferous punctures, setae short and light. Metasternum simply swollen between mesocoxae, metasternal surface polished, setiferous punctures along the inner margin of mesocoxae, metasternal disc with very fine points. Abdomen. Pygidium feebly convex to flat and completely bordered, surface densely and coarsely punctated, punctures with a central pit, several punctures associated with a short and straight seta. Legs. Foretibiae slender, with four external teeth separated at most by two small denticles, basal and external margin with a series of serrate denticles, anterior and internoapical margin of protibiae with an obtuse tooth and few straight setae, apical spur curved downward, tip obtuse. Middle and hind legs unmodified. Male genitalia. In dorsal view, distal-superior area of the paramerites obtusely acuminated at the apex, lateral margin slightly but clearly excavated. In lateral view, distalinferior area of the paramerites swollen and sinuated near the apex, tip of the paramerites slightly curved downward ( Figure 2 (m), 2(n)). Superior margin of the lamella copulatrix straight to feebly concave at middle, superior left lobe narrow and slightly longer than inferior left lobe, narrow and evenly curved outward at the apex, apical margin obtuse. Inferior right lobe distinctly longer than inferior left lobe. Secondary lamella pear-like, with right margin sinuate and narrower at middle and left margin slightly curved, inferior margin widely curved, superior margin truncate. Female genitalia. Ventral sclerotization of the vagina very feeble, central and inferior margin more sclerotized and abruptly curved upward at middle ( Figure 2 (q)).

Females differ from males by the following combination of characters: clypeal margin narrowly curved to clearly sub-trapezoidal and elongated forward, fronto-clypeal carina low, frons with a distinct and sub-trapezoidal carina, which is straight to weakly curved backward at middle. Clypeal surface transversely wrinkled, fronto-clypeal region and frontal surface very densely and more strongly punctated than male. Foretibiae of the female unmodified and larger, anteromedial pronotal region weakly but clearly swollen, last abdominal sternite evenly large at middle.

Minor males are very similar to females and they can often be distinguished in having the frontal carina slightly elevated at both sides and the last abdominal sternite narrower at middle.

Etymology

Refers to the distinctive character observed at the base of the cephalic horns of major males.

Distribution and ecology

To date, only known from north-eastern Ecuador, northern and central Peru, southern Colombia and northern Brazil ( Figure 5 (b)). Species associated with Amazon forests.

Remarks

Although the external morphology of O. basicarinatus may lead one to consider this species to be a close relative of species assigned to the rubrescens complex (e.g. O. rubrescens , O. haematopus and O. onorei ), the examination of the genital organs of both sexes led us to include this species within the osculatii complex. Specifically, the shape of the superior left lobe of the lamella copulatrix, which is very narrow, with sides parallel and apex distinctly acuminated are clear diagnostic signals that suggest close relationships between O. basicarinatus and the remain- der species assigned to the osculatii complex.

Type specimens examined

Holotype (♂ CMNC): 1: COLOMBIA: AMAZONAS. Leticia , Isla Santa Sofia, 215m, 23-II-2- III-1974, J. Kukalova-Peck (printed on white label). 2 : HOLOTYPE: Onthophagus basicarinatus Rossini , Vaz-de-Mello & Zunino, 2018 (printed on red label with black border).

Paratypes (all the specimens listed below bear a yellow label with black border that contains the following information: PARATYPE, Onthophagus basicarinatus Rossini, Vazde-Mello & Zunino, 2018 ):

COLOMBIA: Amazonas: Leticia . Isla Santa Sofia. 215 m . II-III-1974 (53 ♂♂, 50 ♀♀ CMNC; 11 ♂♂, 9 ♀♀ CNCI). BRAZIL: Acre: Cruzeiro do Sul . I-II-1988 (1 ♂ CMNC) . Pará: Abaetetuba . 04-25-VII-1994 (9 ♂♂, 3 ♀♀ CEMT) . Belém. IPEAN. X-1984 (2 ♂♂, 4 ♀♀ CEMT) . Serra dos Carajás . XI-1984 (1 ♂ CEMT) . Mocajuba. Mangabeira. X-XII-1952 (5 ♂♂, 4 ♀♀ CMNC) . ECUADOR: Napo: Estación Cientifica Yasuní . 215 m . 05-10-IX-1999 (1 ♂ TAMU). PERU: Loreto: Miguel Grau . 06°37 ’ 27.4 ” S, 75°3 ’ 54.1 ” W. 140 m (2 ♂♂ IEXA) . San Lorenzo. 17-20-VII (1 ♂, 1 ♀ CEMT) . Ucayalli: San Lorenzo . X-XI-1992 (2 ♂♂, 2 ♀♀ CEMT) .

Figures

Figure 2. Onthophagus transisthmius. (a, b) Dorsal habitus of male and female. (c, d) Dorsal habitus of the holotype and original labels (scale bar: 1 mm). (h, i) Lateral and dorsal view of the parameres (scale bar: 0.05 mm). (j, k) Lamella copulatrix and accessory lamellae. (l) Female genitalia (scale bar: 0.02 mm). Onthophagus basicarinatus sp. nov. (e, f) Dorsal habitus of male (holotype) and female. (g) Detail of the male horns (scale bar: 1 mm). (m, n) Lateral and dorsal view of the parameres (scale bar: 0.05 mm). (o, p) Lamella copulatrix and accessory lamellae (scale bar: 0.02 mm). (q) Female genitalia (scale bar: 0.02 mm).

Figure 5. Geographic distribution of the species of the osculatii complex.