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Artiodactyla is an order of placental mammals composed of even-toed ungulates – hooved animals which bear weight equally on two of their five toes with the other toes either present, absent, vestigial, or pointing posteriorly – as well as their descendants, the aquatic cetaceans. Members of this order are called artiodactyls.
Comparison of even-toed ungulate and cetaceans genetic material has shown that the closest living relatives of whales and hippopotamuses is the paraphyletic group Artiodactyla. [ 7 ] [ 8 ] Dan Graur and Desmond Higgins were among the first to come to this conclusion, and included a paper published in 1994. [ 9 ]
The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. Cetaceans are fully aquatic mammals belonging to the order Artiodactyla and branched off from other artiodactyls around 50 mya.
Cetaceans are deeply nested within the artiodactyls; the two groups together form a clade, a natural group with a common ancestor, for which the name Cetartiodactyla is sometimes used. Modern nomenclature divides Artiodactyla (or Cetartiodactyla) into four subordinate taxa: camelids (Tylopoda), pigs and peccaries (Suina), ruminants (Ruminantia ...
Nevertheless, artiodactyls were far from dominant at that time: the perissodactyls were much more successful and far more numerous. Artiodactyls survived in niche roles, usually occupying marginal habitats, and it is presumably at that time that they developed their complex digestive systems, which allowed them to survive on lower-grade food ...
The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. [2] Cetaceans are fully aquatic mammals belonging to the order Artiodactyla and branched off from other artiodactyls around 50 mya.
The astragalus bone, which is present in the ankle of artiodactyls and archaic whales that retained feet, has similar dimensions in both Eocene artiodactyls and Ichthyolestes. [5] In addition to lending evidence to the theory of a direct relationship between artiodactyls and cetaceans, [ 11 ] this knowledge has led to two competing hypotheses ...
The family Balaenidae, the right whales, contains two genera and four species. All right whales have no ventral grooves; a distinctive head shape with a strongly arched, narrow rostrum, bowed lower jaw; lower lips that enfold the sides and front of the rostrum; and long, narrow, elastic baleen plates (up to nine times longer than wide) with fine baleen fringes.