| Rheiformes | |
|---|---|
| | |
| Greater rhea (Rhea americana) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Infraclass: | Palaeognathae |
| Clade: | Notopalaeognathae |
| Order: | Rheiformes Forbes, 1884 |
| Subgroups [2] | |
| |
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
Today, the order is represented by the sole living genus Rhea , though it contains 4-5 genera in total depending on the affiliation of the extinct genus Diogenornis. The taxonomy of the order is as follows: [9]
Order Rheiformes(Forbes, 1884) Furbringer, 1888 [Rheimorphae Bonaparte, 1849; Rheae Forbes 1884] [10] [11] [12] [13] [14]
The IOC World Bird List (version 15.1) recognizes 2 species of Rheiformes. [15] As of January 2026, IUCN/BirdLife International have assessed both species within the order, but neither have a global population estimate.
| Common name | Binomial name | Population | Status | Trend | Notes | Image |
|---|---|---|---|---|---|---|
| Greater rhea | Rhea americana | unknown [6] | NT [6] | | ||
| Lesser rhea (Darwin's rhea) | Rhea pennata | unknown [7] | LC [7] | The populations of subspecies R. p. tarapacensis and R. p. garleppi are estimated to total 1,000-2,499 mature individuals. The population of the nominate subspecies, R. p. pennata, is expected to be much larger but has not been quantified. [7] | |
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