Onthophagus sancristobalensis Moctezuma and Halffter, 2020

Onthophagus sancristobalensis Moctezuma and Halffter View in CoL , new species

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( Figs. 1 View Fig , 2, 4 View Figs , 6, 7 View Figs )

Type Locality. Mexico, Chiapas, San Cristóbal de Las Casas .

Type Material. Five males, one female. Holotype male: MEXICO: Chiapas: “ 8 kms. N.O. San Cristóbal de Las Casas, Carretera Comitán . 3-XI-74. J. Mateu. Bosque de pino. Alt. 2255 m.” ( GHC) . Paratypes: MEXICO: Chiapas: Same data as holotype ( CMNC: 1 male; GHC: 1 male, 1 female; IEXA: 1 male; VMC: 1 male) .

Description. Holotype male ( Fig. 1 View Fig ). Length 11.5 mm. Dark blue, matte. Head: Dorsal surface roughened, punctate, glabrous. Clypeus concave, transverse. Clypeogenal suture lightly indicated. Genae rounded. Frons slightly convex. Clypeal carina absent. Frontal carina sinuate medially, with 2 strongly developed horns laterally ( Fig. 2 View Figs ). Pronotum: Surface punctate. Integument glabrous, shagreened, without micropunctures. Prominence obtusely trapezoidal, with apex strongly protruded frontally ( Fig. 2 View Figs ). Intermediate tubercles situated on anterior half. Posterior tubercles situated midway. Frontal angles of pronotum acute, lateral angles rounded. Elytra: Striae well-defined, with evenly spaced, rounded punctures. Interstriae glabrous, smooth, superficially punctate; integument shagreened. Pygidium: Surface with roughened punctures, each puncture bearing a conspicuous seta. Integument shagreened. Legs: Protibia elongate, quadridentate, slender, inwardly bent on apical third. Protibial apical spur obliquely curved ventrally. Genitalia: Apex of parameres distinctly notched apically ( Fig. 6 View Figs ). Inferior left lobe and medial keel of endophallite copulatrix poorly developed ( Fig. 7 View Figs ).

Minor Male. Similar to major male except for the reduction of secondary sexual characters (pronotal projection, pronotal tubercles, frontal carina, head horns) and the shorter and wider protibia.

Female. Similar to the male except for the less transverse clypeus; clypeal carina distinctly developed; frontal carina trapezoidal, without horns; pronotal prominence and intermediate tubercles absent; posterior tubercles located in the anterior half of pronotum; and widened protibia ( Fig. 4 View Figs ).

Variation. Mean length from the apex of the clypeus to the pygidium is 8.8 mm ( 8.4–9.1 mm).

Diagnosis. This species is easily recognizable among others of the O. cyanellus species complex by the presence of two strongly developed cephalic horns in major males ( Fig. 2 View Figs ).

Etymology. The specific epithet refers to the type locality.

Distribution and Ecology. Onthophagus sancristobalensis is restricted to the Central Highlands of Chiapas, Mexico, where it occurs in temperate pine forests between 2,200 and 2,300 m elevation ( Fig. 10 View Fig ).

Comments. Zunino and Halffter (1988) considered O. sancristobalensis as a population of O. cyanellus that differed in morphology from the rest of the populations of O. cyanellus ( Figs. 3, 5 View Figs , 8–9 View Figs ): “La población de San Cristóbal de Las Casas, Chiapas, exhibe algunas diferencias morfológicas constantes, representadas principalmente por la acentuación en ambos sexos de los caracteres de las quillas cefálicas, la puntación de disco del pronoto algo más fina, las interestr´ıas elitrales muy débilmente convexas y el aspecto general más distintamente ser´ıceo-mate”. [The population from San Cristóbal de Las Casas, Chiapas, exhibits some constant morphological differences, represented principally by the accentuation in both sexes of the characters of the cephalic carinae, the somewhat finer punctation on the pronotal disc, the very weakly convex elytral interstriae, and the general aspect more distinctly sericeous-matte].

Nevertheless, Zunino and Halffter (1988) commented that the San Cristóbal population did not even deserve subspecific rank because differences in genital morphology were not observed: “No se han revelado diferencias en los aparatos copuladores, por lo que no se considera que dicha población alcance el nivel de subespecie distinta” [Differences in the copulatory apparatus have not been found; therefore, it is not considered that said population attains the level of distinct subspecies]. Nonetheless, the apex of the parameres is frontally notched, and the apex of the inferior left lobe of the endophallite copulatrix is more curved in O. sancristobalensis than in O. cyanellus ( Figs. 6–9 View Figs ). Given the fact that the San Cristóbal population is clearly diagnosable by a unique combination of character states, we consider it a distinctly separate species.

The external and genital morphology of O. sancristobalensis fits well within the O. cyanellus species complex. In particular, the obtusely trapezoidal pronotal prominence in major males is shared with O. cyanellus , leading us to hypothesize a close phyletic relationship between these species, together forming the O. cyanellus species complex. The closely related O. chiapanecus , O. salvadorensis , and O. semiopacus hypothetically form the O. semiopacus species complex as identified by the obtusely triangular pronotal prominence in major males ( Halffter et al. 2019; Joaqui et al. 2019).