4.3.1 | Mylassini, a new tribe of Cryptocephalinae

Mylassa Stål, 1857 is a small, enigmatic genus considered part of the Cryptocephalini, with eight species distributed in Chile and southern Argentina (Jerez & Briones, 2010; Monrós, 1949). The genus, which displays a unique combination of morphological traits both in immature and in adult stages (Agrain et al., 2017; Jerez & Briones, 2010; Monrós, 1949), has been consequently surrounded by taxonomic controversy, early since its inception. Suffrian (1863) synonymized it with Cryptocephalus, a treatment that was followed in most catalogues, as recently as in Seeno and Wilcox (1982). Other authors did not question the validity of the genus, but proposed alternative systematic arrangements either within the Cryptocephalina (Monrós, 1949) or the Pachybrachina (Jacobson, 1924; Schöller, 2000). In all our analyses, M. obliquata appeared consistently as an orphan branch stemming from the basal polytomy of Cryptocephalinae also subtending the four highly supported clades defining the tribes recognized here. Constraining Mylassa to group alternatively with each of these clades did not produce statistically significant differences in the likelihood of the respective optimal trees with the results of the unconstrained analysis (AU test: p =.128–.313). Since we could not discard sister-group relationships or a closer phylogenetic proximity of Mylassa to any of the other four tribes, a most conservative approach is treating this evolutionary lineage with the same rank as the others. Consequently, we formally propose here the new tribe Mylassini trib. n., type genus (by monotypy): Mylassa Stål, 1857, currently with eight species. Diagnosis: long filiform antennae (pectinated in one species) and weakly protruding slightly reniform eyes; posterior border of pronotum with median truncate lobe and devoid of basal margin and crenulation; lateral border of elytron lobed at basal half and surface of elytra pubescent, with ten regular rows of punctures; all femora of similar size and tibiae without apical spurs; unique type of kotpresse most similar to that of the African genus Acolastus Gerstäcker (Agrain et al., 2017; Monrós, 1949; Schöller, 2000).