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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]
Some species, such as sperm whales, are particularly well adapted for diving to great depths to catch squid and other favoured prey. Whales evolved from land-living mammals, and must regularly surface to breathe air, although they can remain underwater for long periods of time.
Scientists believe the first whales evolved over 50 million years ago, according to the University of California, Berkeley's Museum of Paleontology. Today, 92 whale species can be found swimming ...
Though it was known that cetaceans descended from land mammals before the discovery of Ambulocetus, the only evidence of this in the fossil record was the 52-million-year-old (fully terrestrial) Pakicetus and the Paleocene mesonychians (as there was a hypothesised link between cetaceans and mesonychians). The limbs of more aquatic Eocene ...
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.
The larynx evolved when the first land vertebrates started breathing air and needed to separate food from air to prevent choking. Whales evolved from land mammals roughly 50 million years ago.
Cetacea (/ s ɪ ˈ t eɪ ʃ ə /; from Latin cetus ' whale ', from Ancient Greek κῆτος () ' huge fish, sea monster ') [3] is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises.
Whales share this characteristic with extinct marine reptiles, but not present-day marine mammals. [61] A very derived form of hyperphalangy, with six or more phalanges per digit, evolved convergently in rorqual whales and oceanic dolphins, and was likely associated with another wave of signaling within the interdigital tissues. [62]