Two hippopotamuses underwater


It may seem that mostly land-dwelling even-toed ungulates such as giraffes and deer have little in common with exclusively aquatic whales and dolphins. However, recent scientific evidence suggests that cetaceans may have evolved from even-toed ungulate ancestors. Shared origins can now be seen within the fossil record, with early cetaceans possessing a specialised ankle bone that brings together Cetacea and Artiodactyla into a mammalian superorder, Cetartiodactyla. This groups the largest animal ever to have lived (the blue whale) together with the tiny, 2kg mouse deer.

Scientific name: Cetartiodactyla

Rank: Superorder

Cetartiodactyla family tree

An evolutionary tree showing the relationships between hippos, whales and animals with hooves.

An evolutionary tree for the group of mammals known as Cetartiodactyla. When the evolution of mammals is analysed, some surprises emerge - such as the fact that hippos and deer share a common ancestor with whales.


Discover what these behaviours are and how different plants and animals use them.

Viviparous Viviparous
Viviparous animals bear live young that have developed inside the mother's body. Most familiar to us in mammals, there are a few unexpected ocurrences in animal groups usually associated with egg-laying such as reptiles, amphibians, fish and scorpions.

Additional data source: Animal Diversity Web

When they lived

Discover the other animals and plants that lived during the following geological time periods.


  1. Life
  2. Animals
  3. Vertebrates
  4. Mammals
  5. Cetartiodactyla

BBC News about Cetartiodactyla