This order comprises four families. 

Genus-level phylogeny of extant Procellariiformes according to the results of Estandía et al. (2021), with the distribution of each family being indicated by the colour-code used throughout this website (Distribution code). Note that the four genera of Hydrobatidae recognised here may also be united in the broader genus Hydrobates. 

References

Ferrer-Obiol J, James HF, Chesser RT, Bretagnolle V, González-Solís J, Rozas J, Riutort M, and Welch AJ (2021), Integrating sequence capture and restriction site-associated DNA sequencing to resolve recent radiations of pelagic seabirds, Sys. Biol. 70, 976-996. (free pdf)

Ferrer-Obiol J, Herranz JM, Paris JR, Whiting JR, Rozas J, Riutort M, and González-Solis J (2023), Species delimitation using genomic data to resolve taxonomic uncertainties in a speciation continuum of pelagic seabirds, Mol. Phylogenet. Evol. 179, e:107671. (free reading)

Grosser S, Robertson F, Shepherd LD, Tennyson AJD, Miskelly CM, Taylor GA, and Robertson BC (2021), Phylogenetic affinities of the Whenua Hou Diving Petrel: implications for conservation, Emu 121, 102-112. (abstract)

Norambuena HV, Barros R, Jaramillo Á, Medrano F, Gaskin C, King T, Baird K, and Hernández CE (2024), Resolving the conflictive phylogenetic relationships of Oceanites (Oceanitidae: Procellariiformes) with description of a new species, Zootaxa 5486, 451-475. (pdf)

Sausner J, Torres-Mura JC, Robertson J, and Hertel F (2016), Ecomorphological differences in foraging and pattering behavior among storm-petrels in the eastern Pacific Ocean, Auk 133, 397-414. (free pdf)