Rheiformes is an order that contains the family Rheidae (rheas).[3] It is in the infraclass Paleognathae, which contains all ratites. Extant members are found in South America. While the IOC World Bird List and the Clements Checklist categorise Rheiformes as its own order,[3][4] the BirdLife Data Zone includes rheas, along with ostriches, tinamous, cassowaries, emu, and kiwis, in the order Struthioniformes.[5] Of the two extant species of rheas recognized by the IUCN Red List, as of 2022[update], Rhea americana is listed as near threatened,[6] while Rhea pennata is listed as least concern.[7] From 2014 to 2022, the IUCN recognised Rhea tarapacensis as a separate species, and listed it as near threatened in its last assessment in 2020;[8] in 2022, it was again recognised as a subspecies of R. pennata.[7]: Taxonomy
| Rheiformes | |
|---|---|
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| Greater rhea (Rhea americana) | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Infraclass: | Palaeognathae |
| Clade: | Notopalaeognathae |
| Order: | Rheiformes Forbes, 1884 |
| Families[2] | |
| |