This order comprises a single family, Otididae (bustards).
Genus-level phylogeny of extant Otididae, with the distribution of each family being indicated by the colour-code used throughout this website (see Distribution code). The depicted cladogram is based on Cohen (2011), who didn´t provide a timescale.
Cohen C (2011), The phylogenetics, taxonomy and biogeography of African arid zone terrestrial birds: the bustards (Otididae), sandgrouse (Pteroclidae), coursers (Glareolidae) and Stone Partridge (Ptilopachus), Ph.D. Dissertation, University of Cape Town. (pdf)
Yang R, Wu X, Yan P, Su X, and Yang B (2009) Complete mitochondrial genome of Otis tarda (Gruiformes: Otididae) and phylogeny of Gruiformes inferred from mitochondrial DNA sequences, Mol. Biol. Rep. 37 (7), 3057-3066. (pdf)