Diogenornis is an extinct genus of ratites, that lived from the Middle Paleocene[1] to the Early Eocene (Riochican to Casamayoran in the SALMA classification).

[2] It was described in 1983 by Brazilian scientist Herculano Marcos Ferraz de Alvarenga based on fossils found in the Itaboraí Formation in southeastern Brazil.

[4] While initially considered a member of the family Opisthodactylidae, further examination of the fossil remains showed that it was more similar to the modern rhea.

This may reevaluate the origins and distribution of this clade, expanding their range to the South American Paleocene, well before the appearance of Emuarius.

[5] Recent findings nonetheless show that it co-existed with early rheas, meaning the ratite diversity of South America was very high during the Paleogene.