The taxon is represented by ~16 species in a single family, the Pteroclidae. Intrafamiliar relationships are still rather uncertain. 

Genus-level phylogeny of extant Pteroclidae based on Cohen (2011), with the distribution of each species being indicated by the colour-code used throughout this website (Distribution code). The divergence times shown are imaginary and meaningless. 

Provisional genus-level classification of extant Pteroclidae according to the phylogenetic results of Cohen, 2011 (PhD thesis). The classification differs profoundly from the AviList checklist v2025, where all species (except Syrrhaptes paradoxus and S. tibetanus) are included in the genus Pterocles. (link) 

References

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)

Soares AER, Novak BJ, Haile J, Heupink TH, Fjeldsa J, Gilbert MTP, Poinar H, Church GM, and Shapira B (2016), Complete mitochondrial genomes of living and extinct pigeons revise the timing of the columbiform radiation, BMC Evol. Biol. 16: 230. (pdf)