The superorder Palaeognathae is restricted to the order Struthioniformes comprising the following families:

  • Tinamidae (tinamous)
  • Casuariidae (Emu & cassowaries)
  • Apterygidae (kiwi)
  • Rheidae (rheas)
  • Struthionidae (ostriches)

Genus-level timetree of extant Palaeognathae based on Stiller et al. (2024), with the distribution of each family being indicated by the colour-code used throughout this website (Distribution code). The intrinsic phylogeny of Tinamidae follows Almeida et al. (2022) and Musher et al. (2024).

Genus-level classification of extant Palaeognathae. Note that the genera Nothoprocta and Nothura, as currently defined, are not monophyletic. Also note that Musher et al. (2024) provided convincing evidence that Nothoprocta pentlandii is not monophyletic.

Tinamidae (tinamous) are remarkable for being the only volant birds in a group of otherwise cursorial birds. The flying ability, however, is very poor. To date, the phylogenetic position of tinamous within the order couldn’t be resolved with certainty.

Struthionidae (ostriches) are traditionally regarded as a single species, Struthio camelus. However, mitochondrial DNA seems to justify the distinction of two species, Struthio camelus (Common Ostrich) and Struthio molybdophanes (Somali Ostrich). The two species are thought to have separated from each other by the formation of the East African Rift Valley some 4 Ma. 

Extant ostriches are restricted to Africa, while the remaining palaeognaths (Notopalaeognathae) occur in South America, Australia, and New Zealand.

All palaeognaths, except the Struthionidae, exhibit paternal care, with incubation of the eggs relying entirely on the male (Birchard et al., 2013). In ostriches the hen incubates during the day, and the cock during the night. Paternal care is a rather unusual reproductive trait (Owens, 2002). 

Palaeognaths comprise several interesting fossil taxa:

  • Elephant birds (Aepyornithidae) are a recently extinct family from Madagascar that comprised the genera Mullerornis and Aepyornis (Yonezawa et al., 2017). Interestingly, ancient DNA has been extracted from subfossil elephant-bird remains (Grealy et al., 2017; Yonezawa et al., 2017).
  • Moas (Dinornithidae) are an extinct taxon from New Zealand. They probably became extinct some 150 years after Polynesian settlement.
  • Lithornithidae represent an extinct taxon from North America and Europe.


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