ABSTRACT During fieldwork in the Campos Amazônicos National Park, Amazonas state, Brazil, a new endemic species of Mabea was collected in savanna areas. Field collections and specimens in RON, MG, and HRCB were analyzed. To understand the species distribution and verify possible areas of occurrence, niche modeling was conducted using the sdm package in R. Mabea dalyana, the new species is a subshrub with xylopodia and reduced size (less than 1 m height) and small, yellow thyrses. There are several allopatric species of Mabea growing in Amazonian savannas, some widespread but others locally restricted, such as M. uleana from central Amazonia that has some superficial resemblance in leaves and inflorescences but can be distinguished from M. dalyana by pubescent adaxial leaf surface (vs. glabrous), 12-21 submarginal glands (vs. 10 submarginal glands), thyrse brownish to red (vs. yellow thyrse) and conspicuous caruncle (vs. caruncle inconspicuous). M. dalyana is endemic to hyperseasonal savanna, very well adapted to savanna, and fire tolerant. It has notable characteristics, such as a subshrub habit, a xylopodium, glabrous leaves, and sepals noticeably larger than the ovary.

As Euphorbiaceae sensu lato distribuem-se especialmente nos trópicos, nos mais variados tipos de vegetação e habitats, sendo uma das maiores, mais complexas e diversificadas famílias das Angiospermas. Foi recentemente dividida em quatro famílias e segundo os atuais sistemas de classificação, baseados em estudos filogenéticos envolvendo dados moleculares, está assim classificada: Euphorbiaceae sensu stricto, Phyllanthaceae, Putranjivaceae e Picrodendraceae, havendo uma proposição de estabelecer Peraceae, táxon ainda em discussão. Houve também mudanças no posicionamento taxonômico de gêneros de ampla distribuição no território brasileiro, tais como Amanoa, Drypetes, Pera, Phyllanthus, Podocalyx, Pogonophora e Richeria, entre outros. Além disso, novas espécies vêm sendo propostas e a amplitude dos limites de distribuição de diversos táxons vem aumentando no Brasil. Diante do exposto, os autores fornecem um panorama geral dos estudos mais recentes e avanços na taxonomia de Euphorbiaceae s.l. nas regiões Norte, Nordeste, Sudeste e Sul do país, concentrando-se nos trabalhos de revisão e floras regionais, bem como nas mudanças que resultaram em nova configuração taxonômica da família.

The Euphorbiaceae sensu lato are distributed mainly in the tropics, in various types of vegetation and habitats, being one of the largest, most complex and diverse families of angiosperms. It has recently been divided into four families, according to classification systems based on molecular phylogeny: Euphorbiaceae sensu stricto, Phyllanthaceae, Putranjivaceae, and Picrodendraceae. There is a proposition to establish Peraceae still under discussion. There were also changes in the taxonomic position of genera widely distributed in the Brazilian territory, such as Amanoa, Drypetes, Pera, Phyllanthus, Podocalyx, Pogonophora, and Richeria, among others. In addition, new species have been proposed and the limits of taxa distribution are expanding in Brazil. Thus, the authors provide an overview of recent studies and advances in the taxonomy of Euphorbiaceae s.l. in the Northern, Northeastern, Southeastern and Southern regions of Brazil, concentrating on review works and regional floras, as well as the changes that resulted in setting a new taxonomic family.