This superorder contains the following orders and families:
Timetree of Palaeognathae based on Yonezawa et al. (2017), Cloutier et al. (2019), Springer & Gatesy (2019), and Wang et al. (2019), with the distribution of each family being indicated by the colour-code used throughout this website (see Distribution colour code). It is not yet clear whether Rheidae represent the sister-group of all other notopalaeognaths (Yonewawa et al., 2017), of the clade comprising Casuariidae + Apterygidae (Cloutier et al., 2019; Springer & Gates, 2019) or of the Tinamidae (Wang et al., 2019). The depicted phylogeny of Tinamidae represents the molecular tree in Bertelli & Porzecanski (2003).
Scientifically, palaeognaths are the most intriguing and enigmatic bird taxon providing invaluable information for the reconstruction of the avian ground pattern, i.e. the morphology and biology of the first modern bird species. However, uncertainties regarding the origin and evolution of Palaeognathae stem from the difficulty in reliably estimating their phylogenetic interrelationships and in particular their divergence times and their geographical origin. In particular, it still has to be shown whether the present-day distribution is explained by the breakup of Gondwana or by overseas dispersal. Unfortunately, the branching pattern of the extant paleognath phylogeny itself can obviously not answer these questions.
Within palaeognaths, only Tinamiformes 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 still remains to be proven that the 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.
Most 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 particularly interesting fossil taxa:
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.
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)
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)
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)
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.
Lond. B (2002) 357, 283-293. (pdf)
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,
(Rajora, O.P., ed.), pages 1-29, Springer, Cham. DOI: 10.1007/13836_2019_71. (abstract)
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
zone'. bioRxiv, May 21, 2019. doi: http://dx.doi.org/10.1101/643296. (pdf)
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 ratites. Curr. Biol. 27, 68-77. (pdf)