Palaeognathae

Struthioniformes

The superorder Palaeognathae contains only the order Struthioniformes with the following families: 

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

Timetree of 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 restricted to Central and South American, with 46 species in nine genera. Two subfamilies are distinguished: Rhynchotinae (Field Tinamous) and Tinaminae (Field Tinamous). Tinamous are remarkable for being the only volant birds in a group of otherwise flightless birds. However, the flying ability is very poor. 

 


Casuariidae comprise two genera, Dromaius (emus) with only a single species Dromaius novaehollandiae (Emu), and Casuarius (cassowaries) with three species

 

Struthionidae (Ostriches) are represented by a single genus, Struthio, restricted to Africa: 

  • Struthio camelus (Common Ostrich)
  • Struthio molybdophanes (Somali Ostrich)

Traditionally regarded as a single species, Struthio camelus (Ostrich), mitochondrial DNA data seem to justify the distinction of two species, Struthio camelus (Common Ostrich) and Struthio molybdophanes (Somali Ostrich). Common and Somali ostriches are thought to have been sparated by the formation of the East African Rift Valley some 4 mya. Reching a top spead of about 70 km/h, or 45 mph, ostriches are the fastest running birds in the world. 

 

Palaeognaths are the most intriguing and enigmatic clade of birds. Unfortunately, it turned out to be extremely difficult to reconstruct their phylogenetic interrelationships. The only consistent result obtained by molecular data is that Struthionidae branched off first. The intrinsic relationships among the ramining families, the Notopalaeognathae, are still obscure. 

 

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. 

References

Baker, A.J., O. Haddrath, J.D. McPherson, and A. Cloutier (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 A.L. Porzecanski (2003), Tinamou (Tinamidae) systematics: a preliminary combined analysis of morphology and molecules, Ornitol.

Neotrop. 15 (suppl.), 293-299. (pdf)

Bertelli, S., L.M. Chiappe, and G. Mayr (2014), Phylogenetic interrelationships of living and extinct Tinamidae, volant palaeognathous

 birds from the New World, Zool. J. Linn. Soc. 172, 145-184. (abstract)

Birchard, G.F., M. Ruta, and D.C. Deeming (2013), Evolution of parental incubation behaviour in dinosaurs cannot be inferred from clutch mass in birds,

Biol. Lett. 9 (4). (abstract)

Braun, E.L., and R.T. Kimball (2020), Data types and the phylogeny of Neoaves, Preprints 2020, 2020110423. DOI: 10.20994/preprints202011.0423.v1. (pdf)

Cloutier, A., T.B. Sackton, P. Grayson, M. Clamp, A.J. Baker, and S.V. Edwards (2019), Whole-genome analyses resolve the phylogeny of flightless birds

(Palaeognathae) in the presence of an empirical anomaly zone, Syst. Biol. 68(6), 937-955. DOI: 10.1093/sysbio/syz019. (abstract)

Freitag, S. and T.J. Robinson (1993), Phylogeographic patterns in mitochondrial DNA of the Ostrich (Struthio camelus), The Auk 110 (3),

 614-622. Doi:10.2307/4088425(pdf)

Grealy, A., M. Phillips, G. Miller, M.T.P. Gilbert, J.-M. Rouillard, D. Lambert, M. Bunce, and J. Haile (2017), Eggshell palaeogenomics: Palaeognath

evolutionary history revealed through ancient nuclear and mitochondrial DNA from Madagascan elephant bird (Aepyornis sp.) eggshell, Molec. Phylogen. Evol. 109, 151-169. (abstract)

Haddrath, O, and A.J. Baker (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., J. Zoethout, and R.D. Müller (2013), Kinematics of the South Atlantic rift, Solid Earth 4, 215-253. (pdf)

Kuhl, H., C. Frankl-Vilches, A. Bakker, G. Mayr, G. Nikolaus, S.T. Boerno, S. Klages, B. Timmermann, and M. Gahr (2021), An unbiased molecular approach

 using 3'UTRs resolves the avian family-level tree of life, Mol. Biol. Evol. 38(1), 108-127. DOI: 10.1093/molbev/msaa191. (pdf)

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

DOI: 10.1126/science.1251981. (abstract)

Owens, I.P.F. (2002), Male-only care and classical polyandry in birds: phylogeny, ecology and sex differences in remating opportunities. Phil. Trans. R. Soc.

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Pratt, T.K. and B.N. Beehler (2014), "Birds of New Guinea", 2nd edition,  Princeton University Press(link)

Prum, R.O, J.S.Berv, A. Dornburg, D.J. Fields, J.P. Townsend, E.M. Lemmon, and A.R. Lemmon (2015), A comprehensive phylogeny of birds (Aves) using

targeted next-generation DNA sequencing. Nature 526, 569-573. (abstract)

Ramstad, K.M, and L.T. Dunning (2020), Population genomics advances and opportunities in conservation of kiwi (Apteryx spp.)In: Population Genomics,

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Sackton, T.B, P. Grayson, A. Cloutier, Z. Hu, J.S. Liu, N.E. Wheeler, P.P. Gardner, J.A. Clarke, A.J. Baker, M. Clamp, and S.V. Edwards (2019), Convergent

regulatory evolution and loss of flight in paleognathous birds. Science 364, 47-78. DOI: 10.1126/science.aat7244. (link)

Smith, J.V, E.L. Braun, and R.T. Kimball (2013), Ratite nonmonophyly: Independent evidence from 40 novel loci. Syst. Biol. 62(1), 35-49. (pdf)

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

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Wang, Z., J. Zhang, X. Xu, C. Witt, Y. Deng, G. Chen, G. Meng, S. Feng, T. Szekely, G. Zhang, and Q. Zhou (2019), Phylogeny, transposable element and sex

chromosome evolution of the basal lineage of birds. BioRxiv. DOI: 10.1101/750109. (pdf)

Yonezawa, T, T. Segawa, H. Mori, P.F. Campos, Y. Hongoh, H. Endo, A. Akiyoshi, N. Kohno, S. Nishida, J. Wu,H. Jin, J. Adachi, H. Kishino, K. Kurokawa, Y.

Nogi, H. Tanabe, H. Mukoyama, K. Yoshida, A.Rasoamiaramanana, S. Yamagishi, Y. Hayashi, A. Yoshida, H. Koike, F. Akishinonomiya, E. Willerslev, and M. Hasegawa (2017), Phylogenomics and morphology of extinct paleognaths reveal the origin and evolution of the ratitesCurr. Biol. 2768-77. (pdf)

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