Neornithes Gadow, 1893 - living birds Palaeognathae - palaeognaths see Cohort Palaeognathae Pycraft, 1900 ratites see Subcohort Ratitae Merrem, 1813 Family Rheidae Bonaparte, 1849 - rheas Genus Pterocnemia Gray, 1871 [monotypic] Pterocnemia pennata (d'Orbigny, 1834) - lesser rhea Pterocnemia pennata pennataᵀ (d'Orbigny, 1834)