Taxonomic review of theDichotomius mamillatusgroup (Coleoptera: Scarabaeidae), with a description of a new species,Dichotomius(Dichotomius)gandiniisp. nov., from western Amazonia

Abstract

We conducted a morphologically based taxonomic revision of the Dichotomius mamillatus species group (Scarabaeinae). A new species, Dichotomius (Dichotomius) gandinii sp. nov., from western Amazonia is described, illustrated and included in this group, along with Dichotomius (Dichotomius) mamillatus (Felsche, 1901), Dichotomius (Dichotomius) robustus (Luederwaldt, 1935) and Dichotomius (Dichotomius) worontzowi (Pereira, 1942). The external and genital morphology of the mamillatus group and its species are defined through an in‐depth examination of the surviving type material, as well as hundreds of reference specimens deposited in several natural history collections. An illustrated identification key to the Dichotomius species of the group is provided. Pinotus calcaratus Arrow, 1913 (currently Dichotomius calcaratus) is considered to be a junior subjective synonym of Dichotomius (Dichotomius) mamillatus. This research further resolves the many taxonomic questions that are still hampering the correct identification of Dichotomius species in the Neotropics, providing key diagnostic tools for researchers interested in these scarab beetles. The comprehensive morphological study of the D. mamillatus group highlights the important taxonomic value of the often‐overlooked endophallic structures, as well as their central role in informing hypotheses of systematic relationships.

Towards a comprehensive taxonomic revision of the Neotropical dung beetle subgenus Deltochilum (Deltohyboma) Lane, 1946 (Coleoptera: Scarabaeidae: Scarabaeinae): Division into species-groups

“…Recently, Rossini and Vaz-de-Mello [ 74 ]⁠ discussed the relevance of the endophallic structures for taxonomy, reconstruction of evolutionary scenarios and systematics of Scarabaeinae, as well as how these structures aid in a more accurate morphological characterisation of species-groups in Dichotomius Hope, 1838 and which also help to propose, at least initially, hypotheses of systematic relationships. Based on the new characters and on the study of the aedeagus and the endophallus it is possible to hypothesise on potential relationships between the species-groups.…”

Morphometric changes on dung beetle Dichotomius problematicus (Coleoptera: Scarabaeidae: Scarabaeinae) related to conversion of forest into grassland: A case of study in the Ecuadorian Amazonia

“…The genus Dichotomius (Scarabaeidae: Scarabaeinae) are endemic dung beetles from the New World, consisting of approximately 170 named species (Schoolmeesters, 2021 ) that are distributed from the northeastern United States to central Argentina and the highest diversity is found in tropical South America (Nunes & Vaz‐de‐Mello, 2020 ; Rossini & Vaz‐de‐Mello, 2020 ). They are paracoprids and the genus is divided into four subgenera: Dichotomius s.…”

“…Dichotomius problematicus (Rossini & Vaz‐de‐Mello, 2020 )is in the IUCN category of Data Deficient (DD) (Vaz‐de‐Mello et al, 2014 ). There is a lack of information basic about the specific ecological or population dynamics of D. problematicus .…”

“…Dichotomius problematicus (Rossini & Vaz-de-Mello, 2020)is in the IUCN category of Data Deficient (DD) (Vaz-de-Mello et al, 2014).…”

Taxonomic revision of the batesi species group of Dichotomius Hope, 1838, with the description of three new Amazonian species (Coleoptera, Scarabaeidae, Scarabaeinae)

“…The scarcity of taxonomic information has resulted in difficulties for modern biologists who seek to identify species accurately. Many recent papers dealing with taxonomic revisions on Dichotomius species groups have provided redescriptions and diagnoses after careful comparison of types and additional material deposited in collections (Nunes and Vazde-Mello 2013;Maldaner et al 2015;Nunes et al 2016;Valois et al 2017;Arias-Boriticá & Vaz-de-Mello 2019;Nunes & Vaz-de-Mello 2019;Rossini & Vaz-de-Mello et al 2020;Cassenote et al 2020;Montoya-Molina & Vaz-de-Mello 2021). However, in Dichotomius (Selenocopris) such efforts have been concentrated in groups that have practical characteristics for identification, such as: 1) low diversity, with less than ten species; and (2) easy definition based on a distinctive character, such as the presence of metallic coloration (Maldaner et al, 2015), a pair of deep foveae on pronotum (Valois et al 2017), or hairy depression on hypomera (Nunes et al 2016).…”