The taxon comprises ~74 species in three families. 

Genus-level phylogeny of extant Bucerotiformes based on Gonzalez et al. (2013) and Tamashiro et al. (2019). The distribution of each family is indicated by the colour-code used throughout this website (Distribution code). Interfamiliar divergence times have been adopted from Stiller et al. (2024), who considered four bucerotiform genera (Buceros, Bucorvus, Rhinopomastus and Upupa). Intrafamilar divergence times have not been determined yet.

Genus-level classification of extant Bucerotiformes.

References

Gonzalez JCT, Sheldon BC, Collar NJ, and Tobias JA (2013), A comprehensive molecular phylogeny for the hornbills (Aves: Bucerotidae), Mol. Phylogenet. Evol. 67, 468-483. (abstract) (corrigendum)

Kuhl H, Frankl-Vilches C, Bakker A, Mayr G, Nikolaus G, Boerno ST, Klages S, Timmermann B, and Gahr M (2021), An unbiased molecular approach using 3'UTRs resolves the avian family-level tree of life, Mol. Biol. Evol. 38, 108-127. (free pdf)

Tamashiro RA, White NE, Braun MJ, Faircloth BC, Braun EL, and Kimball RE (2019), What are the roles of taxon sampling and model fit in tests of cyto-nuclear discordance using avian mitogenomic data?, Mol. Phylogenet. Evol. 130, 132-144. (abstract)