This work presents a taxonomic revision of Acosmium Schott, including an identification key, descriptions, illustrations, and a distribution map for the taxa. Acosmium is a South American genus with three accepted species: A. cardenasii H.S. Irwin & Arroyo, A. diffusissimum (Mohlenbr.) Yakovlev, and A. lentiscifolium Schott. Acosmium fallax (Taub.) Yakovlev is proposed as a new synonym of A lentiscifolium. In addition, aspects on morphology and specific delimitation in Acosmium, as well as on its geographical distribution, which appears to be strongly associated with the distribution of the seasonally dry tropical forests in South America, are discussed.231164174Ab'Sáber, A.N., Espaços ocupados pela extensão dos climas secos na América do Sul, por ocasião dos períodos glaciais quaternários (1977) Paleoclimas, 3, pp. 1-19Bentham, G., On the genera Sweetia, Sprengel, and Glycine, Linn., simultaneously published under the name of Leptolobium (1865) Journal of the Linnean Society, Botany, 8, pp. 259-267Bentham, G., Leguminosae: Genera Sophoreis Addenda (1870) Flora Brasiliensis, 15 (2), pp. 1-8. , In: C.F.P. Martius & A. Eichler (eds.), Lipsiae, F. FleischerBridson, G.D.R., Smith, E.R., (1991) Botanicum-Periodicum- Huntianum/Supplementum, , Pittisburgh, Hunt Institute for Botanical DocumentationBrummitt, R.K., Powell, C.E., (1992) Authors of Plant Names, , Kew, Royal Botanic GardensFont Quer, P., (1979) Diccionario de Botánica, , Barcelona, Editorial LaborFredericksen, T.S., Pariona, W., Licona, J.C., (2000) Algunos indicadores de la sostenibilidad del aprovechamiento forestal en el manejo de bosques naturales en Bolivia, , Santa Cruz, Chemonics International. Documento técnico 90/2000Harms, H., Leguminosae (1903) Plantae novae americanae imprimis Glaziovianae. Bleiblatt zu den Botanischen Jahrbüchern, 33, pp. 15-33. , In: I. Urban (ed.)Harms, H., Leguminosae (1909) Beiträge zur Flora von Bahia. I. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie, 42, pp. 191-238. , In: E. Ule (ed.)Holmgren, P.K., Holmgren, N.H., Barnett, L.C., (1990) Index Herbariorum, Part 1: The Herbaria of the World, , 8th ed, New York, The New York Botanical Garden PressIrwin, H.S., Arroyo, M.T.K., Three new legumes species from South America (1974) Brittonia, 26, pp. 264-270Lawrence, G.H.M., Buchheim, A.F.G., Daniels, G.S., Dolezal, H., (1968) Botanicum-Periodicum-Huntianum, , Pittisburgh, Hunt Botanical LibraryLewis, G.P., (1987) Legumes of Bahia, , Kew, Royal Botanic GardensMcNeill, J., Barrie, F.R., Burdet, H.M., Demoulin, V., Hawksworth, D.L., Marhold, K., Nicolson, D.H., Turland, N.J., (2007) Código International de Nomenclatura Botânica (Código de Viena) adotado pelo XVII Congresso International de Botânica Viena, Áustria, julho de 2005, , São Carlos, Rima EditoraMereles, M.F., Perez Molas, L., Delmas de Rojas, G., Acosmium cardenasii H. Irwin & Arroyo, Fabaceae- Papilionoideae, nueva mención para la flora paraguaya (2004) Rojasiana, 6, pp. 126-128Mohlenbrock, R.H., A revision of the leguminous genus Sweetia (1963) Webbia, 17, pp. 223-263Oliveira Filho, A.T., Fontes, M.A., Patterns of floristic differentiation among Atlantic forests in Southeastern Brazil and the influence of climate (2000) Biotropica, 32, pp. 793-810Peixoto, A.L., Gentry, A., Diversidade e composição florística da mata de tabuleiro na Reserva Florestal de Linhares (Espírito Santo, Brasil) (1990) Revista Brasileira de Botânica, 13, pp. 19-25Pennington, R.T., Lavin, M., Ireland, H., Klitgaard, B., Preston, J., Hu, J.-M., Phylogenetic relationships of basal Papilionoideae legumes based upon sequences of the chloroplast trnL intron (2001) Systematic Botany, 26, pp. 537-556Pennington, R.T., Prado, D.E., Pendry, C.A., Neotropical seasonally dry forests and Quaternary vegetation changes (2000) Journal of Biogeography, 27, pp. 261-273Pirani, J.R., Diversidade taxonômica e padrões de distribuição geográfica em Picramnia (Simaroubaceae) no Brasil (1990) Acta Botanica Brasilica, 4, pp. 19-44Polhill, R.M., Sophoreae (1981) Advances in Legume Systematics. Part 1, pp. 213-230. , In: R.M. Polhill & P.H. Raven (eds.), Kew, Royal Botanic GardensPrado, D.E., Gibbs, P.E., Patterns of species distributions in the dry seasonal forests of South America (1993) Annals of the Missouri Botanical Garden, 80, pp. 902-927Prance, G.T., Schaller, G.B., Preliminary study of some vegetation types of the Pantanal, Mato Grosso, Brazil (1982) Brittonia, 34, pp. 228-251Radford, A.E., Dickison, W.C., Massey, J.R., Bell, C.R., (1974) Vascular Plant Systematics, , New York, Harper & RowReatto, A., Correia, J.R., Spera, S.T., Solos do Bioma Cerrado: Aspectos pedológicos (1998) Cerrado: ambiente e flora, pp. 47-86. , In: S.M. Sano & S.P. Almeida (eds.), Planaltina, Embrapa-CPACRodrigues, R.S., Tozzi, A.M.G.A., Guianodendron, a new genus of Leguminosae (Papilionoideae) from South America (2006) Novon, 16, pp. 130-133Rodrigues, R.S., Tozzi, A.M.G.A., Morphological analysis and re-examination of the taxonomic circumscription of Acosmium (Leguminosae, Papilionoideae, Sophoreae) (2007) Taxon, 56, pp. 439-452Rodrigues, R.S., Tozzi, A.M.G.A., Systematic relevance of seedling morphology in Acosmium, Guianodendron, and Leptolobium (Leguminosae, Papilionoideae) (2008) Brittonia, 60, pp. 287-296Salis, S.M., Silva, M.P., Mattos, P.P., Silva, J.S.V., Pott, V.J., Pott, A., Fitossociologia de remanescentes de floresta estacional decidual em Corumbá, Estado do Mato Grosso do Sul, Brasil (2004) Revista Brasileira de Botânica, 27, pp. 671-684Schott, H., Fasciculus plantarum brasiliensium (1827) Systema Vegetabilium, 4 (2), pp. 403-410. , In: K.P.J. Sprengel (ed.), 16th ed., (Curae Post.)Silva, G.C., Nascimento, M.T., Fitossociologia de um remanescente de mata sobre tabuleiros no norte do estado do Rio de Janeiro (Mata do Carvão) (2001) Revista Brasileira de Botânica, 24, pp. 51-62Sprengel, K.P.J., (1825) Systema Vegetabilium, 2. , 16th edStafleu, F.A., Cowan, R.S., (1976) Taxonomic Literature, , 2 ed. I-VII. Utrecht: Bohn, Scheltema & HolkemaStearn, W.T., (1992) Botanical Latin, , London, David & Charles Bookvan der Maesen, L.J.G., Primitiae Africanae VIII. A revision of the genus Cadia Forskal (Caes.) and some remarks regarding Dicraeopetalum Harms (Pap.) and Platycelyphium Harms (Pap.) (1970) Acta Botanica Neerlandica, 19, pp. 227-248Vogel, T., Caesalpinieis Brasiliae (1837) Linnaea, 11, pp. 381-416Warwick, M.C., Pennington, R.T., Revision of Cyclolobium (Leguminosae-Papilionoideae) (2002) Edinburgh Journal of Botany, 59, pp. 247-257White, F., The vegetative structure of African Ebenaceae and the evolution of rheophytes and ring species (1998) The Biological Monograph, pp. 95-113. , In: H.C.F. HopkinsC.R. HuxleyC.M. PannellG.T. Prance & F. White (eds.), Kew, Royal Botanic GardensYakovlev, G.P., A review of Sweetia and Acosmium (1969) Notes from the Royal Botanic Garden Edinburgh, 29, pp. 347-355