The southern South American genus Brachysternus Guérin-Méneville is revised and now includes seven species: B. angustus (Philippi and Philippi), B. germaini (Ohaus) new combination, B. marginatus Germain, B. olivaceus Philippi and Philippi, B. patagoniensis Jameson and Smith new species, B. prasinus Guérin-Méneville, and B. spectabilis Erichson. The following species names are new synonyms of B. prasinus: B. vicinus Guérin-Méneville, B. sinuatifrons Germain, B. pubescens Germain, B. viridis Germain, B. dilatatus Germain, B. viridipes Ohaus, and B. hirtus Ohaus. The following species names are new synonyms of B. olivaceus: B. chloris Philippi and Philippi, B. riverae Germain, B. herbaceus Germain, and B. araucanicus Ohaus. The following names were incorrect: “B. viridis Guérin-Méneville” (lapsus calami), “B. viridis Laporte” (lapsus calami), “B. viridis Solier” (incorrect author), and “B. fulvescens Germain” (misapplication). Lectotypes are designated for the following names: B. araucanicus Ohaus, B. chloris Philippi and Philippi, B. dilitatus Germain, B. fulvipes Guérin-Méneville, B. hirtus Ohaus, B. marginatus Germain, B. obscurus Philippi and Philippi, B. olivaceus Philippi and Philippi, B. philippii Germain, B. pubescens Germain, B. riverae Germain, B. spectabilis Erichson, B. vicinus Guérin-Méneville, B. viridipes Ohaus, and B. viridis Germain. Neotypes are designated for B. germaini (Ohaus) and B. prasinus Guérin-Méneville. Keys to adults, diagnostic characters, descriptions, and distributions are presented.

The southern Neotropical genus Hylamorpha (Scarabaeidae: Rutelinae: Anoplognathini: Brachysternina) is comprehensively reviewed. Hylamorpha elegans (Burmeister) is now the only species in the genus with H. cylindrica Arrow entered into new synonymy. Hylamorpha elegans var. australis Philippi is recognized as an unavailable name. Hylamorpha elegans is established as the type species for the genus, and a neotype for H. elegans is designated. Nomenclatural history, descriptions, illustrations, and commentary are included.

Phylogenetic analyses were performed on the 17 taxa in the subtribe Brachysternina (Coleoptera: Scarabaeidae: Rutelinae: Anoplognathini) as a means of resolving classification conflicts and of identifying monophyletic groups. Results demonstrated that the subtribe is monophyletic and is composed of three monophyletic genera: Aulacopalpus Guérin-Méneville (nine species), Brachysternus Guérin-Méneville (seven species), and Hylamorpha Arrow (one species). Characters that define the genera are discussed, and the biogeography of the group is discussed.

The genus Aulacopalpus is revised and now includes A. aconcaguensis new species, A. castaneus (Laporte), A. ciliatus (Solier), A. clypealis Ohaus, A. pilicollis (Fairmaire), A. punctatus (Fairmaire and Germain), A. pygidialis Ohaus, A. valdiviensis new species, and A. viridis Guérin-Méneville. The generic name Tribostethes Curtis is placed in synonymy with the valid name Aulacopalpus Guérin-Méneville; the species name Aulacopalpus fulvovirens Ohaus is placed in synonymy with the valid name Aulacopalpus castaneus (Laporte); the species name Amblyterus variabilis Philippi is placed in synonymy with the valid name Aulacopalpus punctatus (Fairmaire and Germain); and the species name Aegolasia michaelseni Kolbe is placed in synonymy with the valid name Aulacopalpus pilicollis (Fairmaire). Aulacopalpus viridis Guérin-Méneville is designated as the type species for the generic name Amblyterodes Germain. Phytholaema herrmanni herrmanni Germain is designated as the type species for the generic name Melicurus Germain, and the genus is transferred from the Brachysternina to the tribe Xylonychini (Scarabaeidae: Melolonthinae) as a junior synonym of the genus Phytholaema Blanchard. A lectotype is designated for each of the following names: Amblyterus variabilis Philippi, Aulacopalpus clypealis Ohaus, Aulacopalpus fulvovirens Ohaus, Aulacopalpus pygidialis Ohaus, Bembegeneius fulvescens Solier, Tribostethes ciliatus Solier, and Tribostethes pilicollis Fairmaire. A neotype is designated for Aegolasia michaelseni Kolbe, Aulacopalpus viridis Guérin-Méneville, Brachysternus castaneus Laporte, Tribostethes punctatus Fairmaire and Germain, and Tribostethes virens Philippi and Philippi. Descriptions of all species are included. A key to the genera of Neotropical Anoplognathini and species in the genus Aulacopalpus is provided.

The larvae of Platycoelia gaujoni Ohaus and Platycoelia lutescens Blanchard (Coleoptera: Scarabaeidae: Rutelinae) are described. These are the first descriptions of Neotropical Anoplognathini larvae. The character states shared by larval Platycoelia and two previously described Australian Anoplognathini larvae are examined. Character states that separate known Anoplognathini larvae from other Rutelinae tribes are also discussed.

Hybochaetodus flaco Ocampo, new species, from Cusco, Peru is described and illustrated. The genus Hybochaetodus now includes two species, H. flaco and H. obscurus Arrow, both from Peru. The two species are compared and a diagnosis for the genus Hybochaetodus Arrow is provided.