Onthophagus bajacalifornianus Moctezuma and Halffterı, 2019

Moctezuma, Victor & Halffter, Gonzalo, 2019, New biogeographical makeup for colonisation of the Baja California Peninsulaı with the description of a new Onthophagus (Coleoptera: Scarabaeidae: Scarabaeinae), Journal of Natural History 53 (33), pp. 2057-2071 : 2057-2071

Onthophagus bajacalifornianus Moctezuma and Halffterı new species ( Figures 2 – 5 )

Type material

Only two specimens of the new species are known by usı that is the holotype and one paratype. These specimens are deposited in the IEXAı both of them labelled as follows: ‘ Mexicoı B.C.S. Cabo Sn. Lucası 30 mı 9/X/ 2003ı G. Nogueira Col. ’.

Description

Holotype major male ( Figure 2 ). Length 10.6 mmı pronotal width 5.7 mmı elytral width 5.7 mm. Dorsal surface dark blue colouredı mate and dullı with a greenish cast. Head. Dorsal surface glabrous. Clypeus concaveı with the apex rounded. Clypeal punctation coarseı irregular in shape and sizeı transverse and poorly defined towards the apex. Genae slightly projected and rounded. Genal punctation coarseı irregular in shape and size. Clypeo-genal sutures well-marked. Clypeal carina absent. Frons lacking horns or tubercles. Frons coarsely punctateı with circular punctures finer than the clypeal punctures. Frontal carina well developedı trapezoidal in shapeı lacking tubercles or dents. Pronotum. Dorsal surface glabrous. Pronotal prominence obtusely trapezoidalı with the apex blunt. Intermediate tubercles absent. Posterior tubercles strongly developedı located in the mid region of pronotum. Pronotal surface with well-defined circular puncturesı regularly spaced. The central region of pronotal punctures is distinctly glossyı making the tegument quite shiny. Pronotal punctures larger than the head punctures. Pronotal disk with micropunctures finely and shallowly impressed. Pronotal tegument with reticulate microsculpture. Elytra. Elytral striae well-markedı with largeı circular and regularly spaced puncturesı these punctures lacking setae. Interstriae with well- defined and regularly spaced circular puncturesı which are finer than the pronotal puncturesı some punctures bear an inconspicuous setae. Elytral tegument with reticulate microsculpture. Pygidium. Pygidial punctures irregular in size and shapeı becoming more transverse towards the apexı each puncture bearing an inconspicuous setae. Pygidial tegument with reticulate microsculpture. Legs. Protibiae slenderı elongated and inwardly bent in apical thirdı quadridentate. Protibial apical spur obliquely curved ventrally. Genitalia. Parameres external margin shortı wideı apex rounded with a slightly developed indentation that bents downwards ( Figure 3 ). Lamella copulatrix: medial keel ear-shaped; superior left lobe obtusely ovalı non-excavate at the apex; superior right lobe much longer than the left lobe; internal margin of the superior right lobe forming a tooth that bents frontally; apex of the superior right lobe acute ( Figure 4 ).

Variation

Female. Unknown. Minor male. Length 8 mmı pronotal width 4.4 mmı elytral width 4.5 mm. Differs from the major male by the pronotal prominence more acuteı pronotum more concave in the frontal-lateral regionsı showing an obtusely triangular shape; clypeal apex slightly sinuate; frontal carina sinuated mediallyı gradually tapering towards the eyes ( Figure 5 ).

Type locality

Cabo San Lucası Baja California Surı Mexico ( Figure 6 ).

Etymology

The specific epithet derives from the Baja California Peninsulaı where the type series was collected.

Diagnosis

The new species may be easily diagnosed by distributionı being the only one of the O. chevrolati species group occurring in the Baja California Peninsula. Major males of O. bajacalifornianus differ from the rest of the species in the O. chevrolati species group by the following combination of characters: dorsal surface dark blue colouredı mate and dullı with a greenish cast; clypeal carina absent; frontal carina trapezoidalı not sinuated medially; pronotal prominence obtusely trapezoidal; posterior tubercles strongly developedı located on the mid region of pronotum; glossy pronotal punctures; pronotal micropunctures finely and shallowly impressed; apex of parameres rounded with a slightly developed indentation that bents downwards. The new species and those of the O. chevrolati and O. cyanellus species lines only might be diagnosed by a full combination of characters ( Joaqui et al. 2019; Halffter et al. 2019)ı due to the lack of noteworthy autapomorphies.

Natural history

Onthophagus bajacalifornianus seems to be a coprophagous speciesı since it was collected with pitfall traps baited with dung. The type series was collected at approximately 50 m a .s .l . in the San Jose del Cabo areaı where the foothill of the Sierra de la Laguna arises . The mean annual temperature in the type locality is between 18°C and 22° Cı and the annual rainfall is between 300 and 600 mm ( INEGI 2019) . This species seems to be associated with xeric shrublands over a sandy soil area from the southern tip of the Baja Californian Peninsulaı also known as the Cape region ( Figure 6 ) . Onthophagus cartwrighti Howden 1973 also occurs in the Baja California Peninsulaı but its distributional area is not restricted to the southern Peninsula ( Figure 7 ) .

Taxonomical remarks

The new species does not conform to the known supraspecific units defined by Zunino and Halffter (1988a). We decided to assign the new species to its own monotypic lineageı the O. bajacalifornianus species line (see discussion). This new species keys out into the couplet number 12 in Zunino and Halffter (1988a).

Biogeographical distribution pattern

The new species follows the Baja Californian Paleoamerican sub-pattern (see discussion).

Figures

Figure 2. Dorsal habitus of O. bajacalifornianus major male.

Figure 3. Lateral view of the aedeagus of O. bajacalifornianus.

Figure 4. Lamella copulatrix O. bajacalifornianus.

Figure 5. Dorsal habitus of O. bajacalifornianus minor male.

Figure 6. Distribution of O. bajacalifornianus (black dot). Neighbouring species are shown to illustrate the distribution of the O. chevrolati species line (based on Zunino and Halffter 1988a), but they are not hypothesised to have close phyletic relationships with the new species: O. cochisus Brown 1927 (black triangle); O. fuscus Boucomont 1932 (white dot); and O. pseudofuscus Zunino and Halffter 1988a (white triangle). Onthophagus bajacalifornianus shows a vicariant distribution, following the Baja Californian Paleoamerican sub-pattern. The neighbouring species follow the Mountain Paleoamerican subpattern.

Figure 7. Distribution of O. cartwrighti (black dot) and closely related species (based on Howden and Cartwright 1963; Howden 1973; Anduaga and Halffter 1991b; and specimen labels of the Gonzalo Halffter Collection):O. arnetti Howden and Cartwright, 1963 (white triangle), O. browni (black triangle), and O. velutinus (white dot). These species illustrate the penetration of the Baja California Peninsula by the O. mexicanus species group, following the Mexican Plateau Paleoamerican sub-pattern.