Abstract
The gigas species group of the subgenus Canthidium (Neocanthidium) is defined and described. This species group is composed of three described species [C. gigas Balthasar, 1939, Brazilian Atlantic Forest, including intrusions into Cerrado, C. bokermanni (Martínez et al., 1964), Chaco and western Cerrado in Brazil, Bolivia, Paraguay, and Argentina, and C. kelleri (Martínez et al., 1964), Brazilian Cerrado and neighbouring open areas] and three new species: Canthidium stofeli sp. nov. from the western and southern regions of the Brazilian Amazon, Canthidium feeri sp. nov. from French Guiana, and Canthidium ayri sp. nov. from the Brazilian Atlantic Forest. We present descriptions and redescriptions, illustrations, an identification key and comments on the distributions of the species of the gigas group.
Highlights
The genus Canthidium Erichson, 1847 is diagnosed by the presence of nine-articulated antennae with a pubescent club; cylindrical labial palpi; ventral clypeal process usually absent, if present in the form of one longitudinal carina; mesoventrite very short; metaventrite usually convex; and dilation of meso and metatibia with a curved inner margin and an more or less straight outer margin in ventral view (Vaz-de-Mello et al 2011)
Canthidium is currently subdivided into two subgenera, Canthidium s. str. and Neocanthidium Martínez & Halffter, 1986, with some species not presently assigned to any subgenus
Formal species groups have been delimited in several Scarabaeinae genera such as Dichotomius Hope, 1838 (Luederwaldt 1929; Nunes & Vaz-de-Mello 2013), Onthophagus Latreille, 1802 (Zunino & Halffter 1997), Eurysternus Dalman, 1824 (Génier 2009), Ontherus Erichson, 1847 (Génier 1996), and Canthon Hoffmannsegg, 1817 (Halffter & Martínez 1977)
Summary
The genus Canthidium Erichson, 1847 is diagnosed by the presence of nine-articulated antennae with a pubescent club; cylindrical labial palpi; ventral clypeal process usually absent, if present in the form of one longitudinal carina; mesoventrite very short; metaventrite usually convex; and dilation of meso and metatibia with a curved inner margin and an more or less straight outer margin in ventral view (Vaz-de-Mello et al 2011). Due to the large number of species included in many New World dung beetle genera, efforts towards delimiting species groups that facilitate taxonomic revisions are highly desirable. In a preliminary attempt to discriminate some species group within Canthidium, we propose a readily distinguishable species group around Canthidium gigas Balthasar, 1939. Characters defining this group include the large size of its species in relation to the other species of the genus, strongly convex body and uniform black colour. The gigas group includes three previously described species ‒ namely, Canthidium (N.) gigas Balthasar, 1939, C. (N.) bokermanni (Martínez et al, 1964) and C. (N.) kelleri (Martínez et al, 1964), ‒ and three new species described below
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