RESUMO
Despite 12 coccidian species had been recorded from passerines of the Thraupidae family, none of them has been reported in the Parque Nacional do Itatiaia, in Southeastern Brazil. This locality is a protected area with a high degree of vulnerability, and is considered a "conservation island" of biodiversity. The aim of the current work was describe Isospora ramphoceli Berto, Flausino, Luz, Ferreira, Lopes, 2010 from ruby-crowned tanagers Tachyphonus coronatus Vieillot, 1822 in the Parque Nacional do Itatiaia. The oocysts of I. ramphoceli are subspheroidal, 23.1 × 22.1 µm, with smooth, bilayered wall. Micropyle, oocyst residuum and polar granule are absent. Sporocysts are ellipsoidal or ovoidal, 16.2 × 10.8 µm. Stieda body is knob-like and substieda body is large and homogeneous. Sporocyst residuum is composed of many scattered granules. Sporozoites are vermiform with a posterior refractile body and a nucleus. In addition to new locality, this is the first description of I. ramphoceli from T. coronatus.