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Species of the infraorder Cetacea A phylogenetic tree showing the relationships among cetacean families. [1]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]
Arktocara is an extinct genus of river dolphin from the Oligocene epoch of Alaska, containing one species, A. yakataga. Having been discovered in 25-million-year-old strata near the 60th parallel north, it is perhaps the oldest-known crown toothed whale and the northmost river dolphin discovered.
The following is a list of currently existing (or, in the jargon of taxonomy) 'extant' species of the infraorder cetacea (for extinct cetacean species, see the list of extinct cetaceans). The list is organized taxonomically into parvorders , superfamilies when applicable, families , subfamilies when applicable, genus , and then species.
Representing the earliest cetacean radiation, they include the initial amphibious stages in cetacean evolution, thus are the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti. [2] This initial diversification occurred in the shallow waters that separated India and Asia 53 to 45 mya , resulting in some 30 species adapted to a ...
The list of extinct cetaceans features the extinct genera and species of the order Cetacea.The cetaceans (whales, dolphins and porpoises) are descendants of land-living mammals, the even-toed ungulates.
'True' river dolphins are descendants of ancient evolutionary lineages that evolved in freshwater environments. [12] Some species of cetacean live in rivers and lakes, but are more closely related to oceanic dolphins or porpoises and entered fresh water more recently. Such species are considered facultative freshwater cetaceans as they can use ...
This puts mesonychians as a distant relative of cetaceans rather than an ancestor, and their somewhat similar morphology was possibly a result of convergent evolution. The oldest known cetacean is the ambulocetid Himalayacetus identified in 1998 and dated to 52.5 million years ago (predating the terrestrial pakicetids), though the exact dating ...
South Asian river dolphins possess some features that are "primitive" for a cetacean, such as a cecum connected to the gut and air sacs near the blowhole. The testes of the males are located closer to the underside than in marine dolphins and descend more. [15]