The Phanaeus endymion species group is defined as a lineage of dung beetles distributed from Mexico to Ecuador. The current arrangement of the P. endymion species group includes 18 species (five newly described and three revalidated herein): P. arletteae Arnaud, 2018; P. bravoensis Moctezuma, Sánchez-Huerta & Halffter, 2017; P. chiapanecus sp. nov.; P. edmondsi Moctezuma, Deloya & Halffter, 2019; P. endymion Harold, 1863; P. funereus Balthasar, 1939 stat. rev.; P. halffterorum Edmonds, 1979; P. huichol Moctezuma, Sánchez-Huerta & Halffter, 2017; P. jackenioi sp. nov.; P. malyi Arnaud, 2002; P. olsoufieffi Balthasar, 1939 stat. rev.; P. pacificus sp. nov.; P. panamensis sp. nov.; P. porioni Arnaud, 2001 stat. rev.; P. pyrois Bates, 1887; P. rzedowskii sp. nov.; P. zapotecus Edmonds, 2006; and P. zoque Moctezuma & Halffter, 2017. Phanaeus dionysius Kohlmann, Arriaga-Jiménez & Rös, 2018 syn. nov. is considered as a new junior subjective synonymy of P. zapotecus Edmonds, 2006. Phanaeus blanchardi Olsoufieff, 1924 and P. bothrus Blackwelder, 1944 are junior objective synonyms of P. olsoufieffi Balthasar, 1939 stat. rev.

In this study, we take the Onthophagus chevrolati species group, likely a monophyletic species group as an example to analyze the processes that led to the biogeographic integration of the Holarctic fauna in the mountains of the Mexican Transition Zone to test our biogeographic hypotheses. We propose a change from the status of subspecies to species for O. oaxacanus Zunino & Halffter, 1988 new status; O. howdeni Zunino & Halffter, 1988 new status; O. jaliscensis Zunino & Halffter, 1988 new status; O. longecarinatus Zunino & Halffter, 1988 new status; O. omiltemius Bates, 1889 revised status; and O. retusus Harold, 1869 revised status. Consequently, the O. chevrolati group of species is currently made up of 47 species belonging to four species lines: O. vespertilio, O. hippopotamus, O. cyanellus and O. chevrolati. The diversification of the Onthophagus chevrolati species group in this region resulted from three hypothetical stages of evolution. In the first, the penetration and expansion of the ancestor of the O. chevrolati species group occurred before the Miocene and the Trans-Mexican Volcanic Belt arose. During the second stage, the O. hippopotamus species line expanded and evolved, integrating with the paleogeographic changes and the formation of the Trans-Mexican Volcanic Belt, as a consequence of volcanism during the Miocene-Pliocene. In the third and most recent stage, the O. chevrolati species line used the existing mountain systems and interglacial climate fluctuations of the Pleistocene to expand and diversify. Thus, the mountains of the Mexican Transition Zone are not simply periglacial refugia. The entomofauna of Holarctic origin present in the region evolved while the Earth’s geological processes were underway.

The genus Phanaeus is a well-known group whose taxonomy has been described multiple times. Its distribution was previously classified into 11 ecogeographic groups that are equivalent to areas of endemism. Here we use Species Distribution Models to describe species richness patterns. We measured beta-diversity and regionalized its distribution into one region and one transition zone, both with three dominions: Mexican Transition Zone (North American, Mexican, and Mesoamerican dominions) and Neotropical region (Pacific, Brazilian, and Atlantic Forest dominions). We also present a species checklist and updated the distribution maps for 73 of 81 species described so far that reflects all the taxonomical updates. We include a list of all the recorded locations (by country, state, and province), list the recorded habitats and biomes, and describe the modelled environmental conditions for each species.

Two new species of the genusAteuchusWeber are described from the region of Los Chimalapas, Oaxaca, Mexico:A.benitojuarezisp. n.andA.colossussp. n.A diagnosis for distinguishing these new species from the other species of this genus in North America is included. This paper is illustrated with pictures of the dorsal habitus and the male genitalia of the new species. The evolutionary relationships of the species are discussed, as well as their distribution and ecology. It is considered that the species of the genusAteuchuspresent in North and Central America correspond to the Typical Neotropical and Mountain Mesoamerican distribution patterns.

Recent intensive samplings carried out across the mountainous regions of El Pinal (Puebla, Mexico) have provided new insights into the main environmental factors that affect the geographic distribution of the scarabaeinae beetles of the Trans-Mexican Volcanic Belt above 2500 m a.s.l. This study is part of an ongoing project investigating the diversity and biogeography of copro-necrophagous beetles (Scarabaeinae, Aphodiinae, Geotrupinae and Silphidae) in the easternmost areas of the Trans-Mexican Volcanic Belt. Previous experience allows us to propose a series of predictions that we expect will provide possible explanations for current distribution patterns observed in Scarabaeinae and other groups of insects found in the Trans-Mexican Volcanic Belt. This mountain range has a primarily biogeographic importance, limiting the Mexican High Plateau in the South and connecting the western and eastern Sierra Madre mountain chains, which are considered the most important routes for dispersal of mountain fauna of northern origin. The taxonomic and biogeographic study of the species collected so far in El Pinal (including Onthophagus clavijeroi sp. n. and Onthophagus martinpierai sp. n. described here), along with their possible relationships with other known species, allows us to answer the preliminary assumptions proposed.