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

  • Tinamidae (Tinamous)
  • Casuariidae (Emu and Cassowaries)
  • Apterygidae (Kiwis)
  • Rheidae (Rheas)
  • Struthionidae (Ostriches)

Genus-level timetree of extant Palaeognathae based on Prum et al. (2015), and Kuhl et al. (2021), with the distribution of each family being indicated by the colour-code used throughout this website (see Distribution code). The divergence times follow Kuhl et al. (2021), and differ significantly from Prum et al. (2015). The intrinsic phylogeny of Tinamidae represents the molecular tree in Bertelli & Porzecanski (2003) and partly Wang et al. (2019) .  


Tinamidae (tinamous) are remarkable for being the only volant birds in a group of otherwise flightless birds. However, the flying ability is very poor. Unfortunately, the phylogenetic position of tinamous within Struthioniformes couldn‘t be clarified yet, despite considerable efforts. 

Struthionidae (Ostriches) are traditionally regarded as a single species, Struthio camelus (Ostrich). However, mitochondrial DNA seems to justify the distinction of two species, Struthio camelus (Common Ostrich) and Struthio molybdophanes (Somali Ostrich). Somali ostriches are thought to have sparated from each other by the formation of the East African Rift Valley some 4 mya. Reaching a top spead of about 70 km/h, or 45 mph, ostriches are the fastest running birds in the world.

Within palaeognaths, only Tinamidae are capable of flight whereas other palaeognaths are strictly cursorial. Therefore, the ability to fly either must have been lost several times, or must have been gained independently from neognathous birds by tinamous. It should be noted, however, that tinamous are extremely poor and reluctant flyers, unable to fly for extended periods. Thus, it remains unclear whether ancestral Palaeognathae were volant. 


Extant ostriches are restricted to Africa, while notopalaeognaths occur in South America, Australia, and New Zealand. The simplest explanation for this disjunct distribution is to assume that the ancestral notopalaeognath once happened to enter South America, either via Africa or via Central America. 


All palaeognaths, with the exception of Struthionidae, show paternal care, with incubation of the eggs relying entirely on the male (Birchard et al., 2013, fig.2). Paternal care is a fairly unusual reproductive trait that occurs in species where remating opportunities are rare for both sexes and particularly scarce for males (Owens, 2002). In ostriches, on the other hand, the hen incubates during the day and the cock during the night. 

Palaeognaths comprise a number of interesting fossil taxa: 

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


Baker AJ, Haddrath O, McPherson JD, and Cloutier A (2014), Genomic support for a Moa-Tinamou clade and adaptive morphological convergence in flightless Ratites, Mol. Biol. Evol. 31, 1686-1696. (pdf)


Bertelli S, and Porzecanski AL (2003), Tinamou (Tinamidae) systematics: a preliminary combined analysis of morphology and molecules, Ornitol. Neotrop. 15 (suppl.), 293-299. (pdf)


Bertelli S, Chiappe LM, and Mayr G (2014), Phylogenetic interrelationships of living and extinct Tinamidae, volant palaeognathous birds from the New World, Zool. J. Linn. Soc. 172, 145-184. (abstract)


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Cloutier A, Sackton TB, Grayson P, Clamp M, Baker AJ, and Edwards SV (2019), Whole-genome analyses resolve the phylogeny of flightless birds  (Palaeognathae) in the presence of an empirical anomaly zone, Syst. Biol. 68, 937-955. (abstract)


Freitag S, and Robinson TJ (1993), Phylogeographic patterns in mitochondrial DNA of the Ostrich (Struthio camelus), The Auk 110, 614-622. (pdf)


Grealy A, Phillips M, Miller G, Gilbert MTP, Rouillard JM, Lambert D, Bunce M, and Haile J (2017), Eggshell palaeogenomics: palaeognath evolutionary history revealed through ancient nuclear and mitochondrial DNA from Madagascan elephant bird (Aepyornis sp.) eggshell, Mol. Phylogen. Evol. 109, 151-169. (abstract)


Haddrath O, and Baker AJ (2012), Multiple nuclear genes and retroposons support vicariance and dispersal of the palaeognaths, and Early Cretaceous origin of modern birds. Proc. Royal Soc. B 279, 4617-4625. (pdf)


Heine C, Zoethout J, and Müller RD (2013), Kinematics of the South Atlantic rift, Solid Earth 4, 215-253. (pdf)


Kuhl H, Frankl-Vilches C, Bakker A, Mayr G, Nikolaus G, Boerno ST, Klages S, Timmermann B, and Gahr M (2021), An unbiased molecular approach using 3'UTRs resolves the avian family-level tree of life, Mol. Biol. Evol. 38, 108-127. (pdf)


Mitchell KJ et al. (2014), Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution, Science 344, 898(abstract)


Owens IPF (2002), Male-only care and classical polyandry in birds: phylogeny, ecology and sex differences in remating opportunities, Phil. Trans. R. Soc. Lond. B (2002) 357, 283-293(pdf)


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Sackton TB, Grayson P, Cloutier A, Hu Z, Liu JS, Wheeler NE, Gardner PP, Clarke JA, Baker AJ, Clamp M, and Edwards SV (2019), Convergent regulatory evolution and loss of flight in paleognathous birds. Science 364, 47-78. (link)


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Springer MS, and Gatesy J (2019), Retroposon insertions within a multispecies coalescent framework suggest that ratite phylogeny is not in the 'anomaly zone'. bioRxiv, . (pdf)


Wang Z, Zhang J, Xu X, Witt C, Deng Y, Chen D, Meng G, Feng S, Szekely T, Zhang G, and Zhou Q (2019), Phylogeny, transposable element and sex  chromosome evolution of the basal lineage of birds. BioRxiv. (pdf)


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