Artiodactyla

Artiodactyla is the mammalian order traditionally called even-toed ungulates, including pigs, camels, ruminants, whales, and dolphins. Its living members are often classified within the broader clade Cetartiodactyla.

Ungulate: A hoofed mammal, or a member of a broader group traditionally associated with hoofed mammals. Artiodactyla is one of the principal mammalian groups historically recognized as ungulates.
Astragalus: A bone in the ankle that articulates with the tibia and forms part of the hind-foot joint. Its distinctive pulley-like ends helped identify fossil artiodactyls.
Suina: A suborder of artiodactyls that includes pigs and peccaries. Suines retain a non-ruminant body plan unlike that of most familiar hoofed relatives.
Even-toed ungulate: A traditional name for hoofed mammals whose weight is borne mainly by the third and fourth toes. The name describes the typical foot structure but excludes the hoofless descendants, whales.
Whale evolution: The evolutionary history through which terrestrial mammals became fully aquatic cetaceans. Whale evolution explains why a group once defined by hooves includes animals without limbs or hooves.
Mammalian taxonomy: The classification of mammals into nested groups based on shared ancestry and distinguishing traits. Artiodactyla’s limits depend on whether classification follows traditional anatomy or evolutionary relationships.
Molecular phylogenetics: The reconstruction of evolutionary relationships using comparisons of DNA, RNA, or protein sequences. Molecular trees established cetaceans as nested within the artiodactyl lineage.
Tylopoda: A suborder of artiodactyls that includes camels and their extinct relatives. Camelids represent a distinctive lineage outside the ruminant group.
Pakicetus: An extinct early whale from the Eocene of South Asia, known from fossils including a largely terrestrial skeleton. Pakicetus documents an early stage in the evolutionary transition toward cetaceans.
Phylogenetic nomenclature: A system of naming biological groups according to evolutionary relationships and ancestry. The placement of cetaceans raised questions about whether Artiodactyla should include all descendants of its common ancestor.

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