Onthophagus humboldti, Kohlmann, Bert, Solis, Angel & Alvarado, Guillermo E., 2019

Kohlmann, Bert, Solis, Angel & Alvarado, Guillermo E., 2019, Description of Onthophagus humboldti and Uroxys bonplandi, two new scarab beetles (Coleoptera, Scarabaeidae, Scarabaeinae) from Costa Rica, with notes on tropical mountain brachyptery and endemicity, ZooKeys 881, pp. 23-51 : 25-29

publication ID	https://dx.doi.org/10.3897/zookeys.881.38026
publication LSID	lsid:zoobank.org:pub:ADCA057E-3E1B-45D8-B5C9-665683F51B59
persistent identifier	https://treatment.plazi.org/id/C13D9441-5A22-4CA1-974F-88B6A97199AC
taxon LSID	lsid:zoobank.org:act:C13D9441-5A22-4CA1-974F-88B6A97199AC
treatment provided by	ZooKeys by Pensoft
scientific name	Onthophagus humboldti
status	sp. nov.

Treatment

Onthophagus humboldti sp. nov. Figures 1 View Figure 1 , 2a, c, e View Figure 2 , 3a, c View Figure 3 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 9 View Figure 9

Type locality.

Costa Rica. Prov. Puntarenas. Buenos Aires, P.N. La Amistad. Tres Colinas.

Type deposition.

Museo Nacional de Costa Rica, Santo Domingo de Heredia, Costa Rica.

Type material.

Holotype male, pinned, with genitalia in a separate microvial. Original label: "Costa Rica. Provincia Puntarenas. Buenos Aires, Parque Nacional La Amistad. Tres Colinas. 2100-2200 m. 27-29 Febrero 2008. A. Solís, M. Moraga. Trampa Foso. L S 343850 565700." "HOLOTYPE/ Onthophagus humboldti Kohlmann, Solís, Alvarado [red printed label]".

Other material.

Paratypes. (8 males, 4 females). "Costa Rica. Provincia Puntarenas. Buenos Aires, Parque Nacional La Amistad. Tres Colinas. 2100-2200 m. 27-29 Febrero 2008. A. Solís, M. Moraga. Trampa Foso. L S 343850 565700."

Diagnosis.

Elytra as long as or shorter than pronotum ( Fig. 1 View Figure 1 ), due to brachyptery ( Fig. 3c View Figure 3 ). Broad clypeal horn bifurcation ( Fig. 2a View Figure 2 ); pygidium and apex of elytra with evident setae; clypeal margin indented at junction with clypeo-genal suture ( Fig. 2e View Figure 2 ).

Description.

Holotype. Male ( Fig. 1 View Figure 1 ), length 7.2 mm; maximum width 4.3 mm. Oval, shining reddish black. Centre of the clypeus projected forming a slender bifid horn ( Figs 1 View Figure 1 , 2c View Figure 2 ); genae projected forming an angle ( Fig. 2e View Figure 2 ), genal sutures almost effaced; head punctures coarse, regular, dense, becoming finer and sparser towards the center; clypeal carina absent, vertex carina substituted by two vertical asymmetric platelets, modestly developed, and obliquely oriented; eyes two times longer than wide and separated by eight times the eye width.

Pronotum ( Fig. 2c View Figure 2 ) very convex, lateral margins with a small and irregular fovea, not lineal; lateral pronotal margins bordered by a deep sulcus, anterior and basal borders margined; pronotal surface reticulate and covered by dense, regular, coarse, annular, and deep punctures without setae; pronotal projection well-developed ( Figs 1 View Figure 1 , 2c View Figure 2 ), forming a broad bilobed plate slightly bent downwards, with a depressed area antero-centrally, and having clear antero-lateral margins; anterior angles projected as long, slender, and curved projections ( Figs 1 View Figure 1 , 2c View Figure 2 ); pronotal base with a sulcus extending forward one third its length; scutellum not visible between the base of the elytra.

Elytra convex, with clear margins and without a humeral callus; with eight well-marked striae, fine and clearly impressed and with crenulating punctures; intervals clearly punctured, punctures big and dense, not aligned, bearing short, stiff setae along the lateral and apical margins; microsculpture reticulate and regular. Wing brachypterous, measuring 0.75 mm ( Fig. 3c View Figure 3 ). Pygidium moderately shiny and shagreen, margined border, with big, coarse, annular punctures bearing short and stiff setae. Aedeagus as Fig. 3a View Figure 3 .

Mesosternum with evident annular punctures bearing no setae. Metasternum shagreen and finely punctured, more coarsely laterally, basal third with a sulcus. Abdominal segments shagreen and finely punctured.

Fore femur long, slender, and punctured; meso- and metafemur short and elongate, light yellow. Fore tibia long, slender and arched ( Fig. 1 View Figure 1 ); with four external teeth; tibial spur elongated, straight, pointed, deflexed anteriorly, extending to second tarsal segment. Middle- and hind femur light yellow at middle.

Female, length 6.3 mm; maximum width 3.6 mm. It is similar to the male and varies in having a clypeus not forming a horn, clypeus shagreen, genae not projected as teeth, with a head frons keel, two small platelet projections at head vertex, no pronotal projection, no projected pronotal anterior angles, fore tibia short, fore femur short, last abdominal sternite broad.

Variation.

Length 5.6 to 7.2 mm. Width 3.2 to 4.3 mm. Small males do not have the bifid clypeal horn, just a small erect lamella; vertex platelets forming a small projection; anterior pronotal angles not projected, pronotal projection forming a small carina. Body color varying from black to piceous red.

Etymology.

This species is dedicated in honor of Friedrich Wilhelm Heinrich Alexander von Humboldt, Prussian geographer, explorer, and naturalist, commemorating the 250th anniversary of his birth. He is widely recognized for fathering the work on physical and plant geography, which laid the foundation for the development of modern biogeography.

Taxonomic considerations.

Kohlmann and Solís (2001) report the existence of 39 species of Onthophagus for Costa Rica. This new species would increase their numbers to 40. Onthophagus humboldti sp. nov. belongs to the Onthophagus dicranius Bates species group, as defined by Kohlmann and Solís (2001).

Onthophagus humboldti sp. nov. will key out to O. micropterus Zunino & Halffter, 1981, in Kohlmann and Solís´ key ( 2001). It can be easily differentiated by the following characteristics: In males clypeal horn slender at middle and very bifurcated at apex ( Fig. 2a View Figure 2 ) ( O. humboldti sp. nov.) versus broad at middle and notched at apex ( Fig. 2b View Figure 2 ) ( O. micropterus ); genae projected forming an angle ( Fig. 2e View Figure 2 ) ( O. humboldti sp. nov.) versus genae projected forming a tooth ( Fig. 2f View Figure 2 ) ( O. micropterus ); vertex platelets forming a carina ( O. humboldti sp. nov.) versus a pointed projection ( O. micropterus ); anterior lateral angles of pronotum projected as long, slender, and curved projections ( Fig. 2c View Figure 2 ) ( O. humboldti sp. nov.) versus a short, curved projection ( Fig. 2d View Figure 2 ) ( O. micropterus ); pronotal central forward projection well-developed, forming a broad bilobed plate slightly bent downwards ( Fig. 2c View Figure 2 ) ( O. humboldti sp. nov.) versus a bilobed plate projecting forward ( Fig. 2d View Figure 2 ) ( O. micropterus ). In females: vertex platelets forming a carina ( O. humboldti sp. nov.) versus a pointed projection ( O. micropterus ).

Geographical distribution.

This species is so far only known from the area of Tres Colinas, near Buenos Aires, in the province of Puntarenas ( Fig. 5 View Figure 5 ). It has been collected from 2100 to 2200 m altitude in the month of February in lower montane rain forest.

Chorological affinities.

Onthophagus humboldti sp. nov. is endemic to the Cordillera de Talamanca and is the tenth known brachypterous Onthophagus species to be described worldwide. A closely related species, O. micropterus , is also distributed in the Cordillera de Talamanca ( Fig. 6 View Figure 6 ), from 2100 to 3000 m altitude in tropical mountain rainforest and has been collected from October to February.

Biogeography.

This species belongs to the O. dicranius species group, as established by Kohlmann and Solís (2001). This group of species has extra-American affinities, in which Howden and Gill (1993) indicate that the American fauna of Onthophagus is the result of invasive species from East Asia and that the O. dicranius group presents characters in common with New Guinea species. This agrees with the hypothesis originally proposed by Zunino and Halffter (1988), which points out for the supraspecific groups of American Onthophagus , an origin of its lineages, which in the case of the current representatives is distributed in East or Southeast Asia; and for this case, the Asian representation of the ancestral line, like the American one, has its distribution present in the humid tropics. On the other hand, the O. dicranius species group has its present-day center of diversity in tropical North America and relatives in South America ( Zunino and Halffter 1997; Kohlmann and Solís 2001).

This situation seems to be in congruence with the boreotropical distribution hypothesis ( Wang 1961; Wolfe 1975; Lavin and Luckow 1993; Xiang and Soltis 2001; Davis et al. 2002), where current flora groups show a tropical disjunct distribution, generally centered in America, Africa, and tropical Asia. This hypothesis is based on the observation of the existence of tropical broadleaf forests during the Early Paleogene (in old Stratigraphy terminology, Early Tertiary) at high latitudes in regions that are currently temperate, directed by a Late Paleocene-Early Eocene thermal maxima (ca. 52 ma, Zachos et al. 2001) and that many current angiosperm temperate taxa have evergreen relatives in subtropical rainforests ( Axelrod 1966). This proposal then suggests the existence of northern bridges that were once at lower latitudes, such as the Bering Bridge during the Early Paleogene and the North Atlantic Bridge during the Eocene, which may have served as migration routes for groups of organisms that currently present intercontinental disjunct distributions. This hypothesis suggests that a taxon with a present-day center of diversity in tropical North America, and with an early Paleogene fossil record from any region there, has a high probability of having sister-group relatives in the Paleotropics and derived relatives in South America ( Lavin and Luckow 1993).

This pattern of distribution would clarify those proposed by Halffter ( Halffter and Morrone 2017) for the "Mexican Transition Zone" in particular one of them, the so-called "Paleoamerican Dispersion Pattern" ( Halffter 1964). This pattern of dispersion corresponds to northern taxa that arrived in North America from Eurasia, and has been subdivided by Halffter et al. (1995) into four variants, where one of them, called the "Paleoamerican Tropical Pattern", corresponds to species found in the lowlands of the tropics and at medium altitudes, their distribution being very similar to that of the Neotropical pattern, but their affinities are with the Old World taxa. Halffter et al. (1995, 2008) placed the Onthophagus clypeatus and> Onthophagus dicranius species groups of the genus Onthophagus within this pattern.

Actually, the groups of species mentioned above are congruent with the typical characteristics of the so-called boreotropical distribution. Therefore, the aforementioned distribution variant, the "Paleoamerican Tropical Pattern", seems to be the same with the boreotropical distribution and it is proposed here to use the term boreotropical distribution from now on as it is a more complete and well-founded concept, besides being an older one. This pattern has been studied and characterized at very fine phylogenetic and biogeographic analysis levels in animal and plants ( Lidgard and Crane 1990; Xiang and Soltis 2001; Davis et al. 2002; Feng et al. 2009; Guo et al. 2012; Ye et al. 2016).