Cetartiodactyla is a group comprised of two orders of mammals that are superficially quite different and that, until recently, were recognized as two separate monophyletic clades. These orders are Artiodactyla, the even-toed ungulates, including animals such as cows (Bovidae), camels (Camelidae), and deer (Cervidae), and Cetacea, a group of mammals that are highly specialized for an aquatic lifestyle, including whales, dolphins (Delphinidae), and porpoises (Phocoenidae). Recent molecular evidence suggests that Cetacea evolved from artiodactyl ancestors. Making Artiodactyla non-monophyletic unless Cetacea is included. Experts suggest the monophyletic clade representing artiodactyls and cetaceans be called Cetartiodactyla. (Boisserie, Lihoreau, and Brunet, 2005; Gatesy et al., 1996; Gatesy et al., 1999; Gatesy, 1997; Graur and Higgins, 1994; Milinkovitch and Thewissan, 1997; Montgelard, Catzeflis, and Douzery, 1997; Naylor and Adams, 2001; O'Leary and Geisler, 1999; Shimamura et al., 1997; Thewissen, Williams, and Hussain, 2001)
- O'Leary, M., J. Geisler. 1999. The position of Cetacea within Mammalia: Phylogenetic analysis of morphological data from extinct and extant taxa. Systematic Biology, 48(3): 455-490.
- Graur, D., D. Higgins. 1994. Molecular evidence for the inclusion of cetaceans within the order Artiodactyla. Molecular Biology and Evolution, 11(3): 357-364.
- Montgelard, C., F. Catzeflis, E. Douzery. 1997. Phylogenetic relationships of artiodactyls and cetaceans as deduced from the comparison of cytochrome b and 12S rRNA mitochondrial sequences. Molecular Biology and Evolution, 14(5): 550-559.
- Gatesy, J. 1997. More DNA support for a Cetacea/Hippopotamidae clade: The blood-clotting protein gene Y-Fibrinogen. Molecular Biology and Evolution, 14(5): 537-543.
- Shimamura, M., H. Yasue, K. Ohshima, H. Abe, H. Kato, T. Kishiro, M. Goto, I. Munechika, N. Okada. 1997. Molecular evidence from retroposons that whales form a clade within even-toed ungulates. Nature, 388: 666-670.
- Gatesy, J., C. Hayashi, M. Cronin, P. Arctander. 1996. Evidence from milk casein genes that cetaceans are close relatives of hippopotamid artiodactyls. Molecular Biology and Evolution, 13(7): 954-963.
- Thewissen, J., E. Williams, S. Hussain. 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature, 413: 277-281.
- Boisserie, J., F. Lihoreau, M. Brunet. 2005. The position of Hippopotamidae within Cetartiodactyla. Proceedings of the National Academy of Sciences, 102: 1537-1541.
- Gatesy, J., M. Milinkovitch, V. Waddell, M. Stanhope. 1999. Stability of cladistic relationships between Cetacea and higher-level artiodactyl taxa. Systematic Biology, 48(1): 6-20.
- Milinkovitch, M., J. Thewissan. 1997. Even-toed fingerprints on whale ancestry. Nature, 388: 622-624.
- Naylor, G., D. Adams. 2001. Are the fossil data really at odds with the molecular data? Morphological evidence for Cetartiodactyla phylogeny reexamined. Systematic Biology, 50(3): 444-453.