A new species of dragon's blood Croton (Euphorbiaceae) from Serra dos Órgãos (Rio de Janeiro, Brazil).

Crotonrizzinii Farias & Riina, sp. nov. is a new species from Serra dos Órgãos National Park in the Atlantic Rain Forest domain (Rio de Janeiro state, Brazil). It is known from the municipalities of Guapimirim, Teresópolis and Petrópolis, where it grows in montane ombrophilous dense forest, between 500 and 1500 m elevation. This arborescent species belongs to CrotonsectionCyclostigma Griseb., a Neotropical lineage distributed in forest habitats from Mexico to northern Argentina. It is mainly characterised by its laciniate-glandular stipules, bracts with two inconspicuous glands (colleters) at the base and campanulate pistillate flowers with sepals covering the ovary. We describe and illustrate the new species, and compare it with close relatives occurring in the Atlantic Rain Forest. We also provide a distribution map, habitat information and suggestions for the assessment of its conservation status.