Type series for 35 type species of Macrodactylini (Coleoptera: Scarabaeidae: Melolonthinae) are studied and taxonomic changes are proposed. The following 35 lectotypes are designated: Agaocnemis pruina Moser, 1918; Amphicrania ursina Burmeister, 1855; Anomalochilus singularis Blanchard, 1850; Anomalonyx uruguayensis Moser, 1921; Aulanota sulcipennis Moser, 1924; Barybas nanus Blanchard, 1850; Barybas volvulus Burmeister, 1855; Calodactylus tibialis Blanchard, 1850; Ceraspis pruinosa LePeletier de Saint-Fargeau & Audinet-Serville, 1828; Ceratolontha venezuelae Arrow, 1948; Chariodactylus chacoensis Moser, 1919; Clavipalpus dejeani Laporte, 1832; Corminus canescens Burmeister, 1855; Ctenotis obesa Burmeister, 1855; Ctilocephala pellucens Burmeister, 1855; Demodema fallax Blanchard, 1850; Euryaspis gaudichaudii Blanchard, 1851; Faula cornuta Blanchard, 1850; Gama grandicornis Blanchard, 1850; Gastrohoplus mirabilis Moser, 1921; Mallotarsus spadiceus Blanchard, 1850; Manodactylus gaujoni Moser, 1919; Manopus biguttatus Conte de Castelnau, 1840; Melolontha rufipennis Fabricius, 1801; Oedichira pachydactyla Burmeister, 1855; Pachycerus castaneipennis Guérin-Méneville, 1831; Pachylotoma viridis Blanchard, 1850; Pectinosoma elongata Arrow, 1913; Philochlaenia virescens Blanchard, 1842; Plectris tomentosa LePeletier de Saint-Fargeau & Audinet-Serville, 1828; Pseudohercitis viridiaenea Moser, 1921; Rhinaspoides aeneofusca Moser, 1919; Schizochelus flavescens Blanchard, 1850; Serica marmorea Guérin-Méneville, 1831; and Ulomenes hypocrita Blanchard, 1850. The following six genera are revalidated: Byrasba Harold, 1869 (formerly a synonym of Rhinaspis Perty, 1833); Euryaspis Blanchard, 1851 (formerly a synonym of Plectris LePeletier de Saint-Fargeau & Audinet-Serville, 1828); Junkia Dalla Torre, 1913 (formerly a synonym of Plectris); Faula Blanchard, 1850 (formerly a synonym of Ceraspis LePeletier de Saint-Fargeau & Audinet-Serville, 1828); Paulosawaya Martínez & d’Andretta, 1956 (formerly a synonym of Clavipalpus Laporte, 1832); and Pseudoserica Guérin-Méneville, 1838 (formerly a synonym of Plectris). The following 11 new generic synonymies are proposed: Anomalochilus Blanchard, 1850 a new synonym of Plectris; Amphicrania Burmeister, 1855 (formerly a synonym of Clavipalpus and a homonym of Amphicrania Dejean, 1833) and Pseudoleuretra Martínez & d’Andretta, 1956 are synonymized with Paulosawaya; Aulanota Moser, 1924 and Hadrocerus Guérin-Méneville, 1838 are synonymized with Philochloenia; Ctenotis Burmeister, 1855 a new synonym of Euryaspis Blanchard, 1851; Gama Blanchard, 1850, Pachylotoma Blanchard, 1850 (formerly a synonym of Gama) and Harpodactyla Burmeister, 1855 (formerly a synonym of Gama) are synonymized with Pseudoserica; Gastrohoplus Moser, 1921 a new synonym of Schizochelus Blanchard, 1850; and Hercitis Burmeister, 1855 a new synonym of Barybas Blanchard, 1850. One new specific synonymy is proposed: Hercitis pygmaea Burmeister, 1855 a synonym of Barybas nana Blanchard, 1850. Philochloenia armata nom. nov. is proposed for Aulanota sulcipennis Moser, 1924 to avoid secondary homonymy. Ancistrosoma Curtis, 1835, nomen protectum, has priority over Sciuropus Dejean, 1833, nomen oblitum. Taxonomic remarks, diagnoses and a key are given to all Macrodactylini genera.