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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]
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.
Cetacean eyes are set on the sides rather than the front of the head. This means only species with pointed 'beaks' (such as dolphins) have good binocular vision forward and downward. Tear glands secrete greasy tears, which protect the eyes from the salt in the water. The lens is almost spherical, which is most efficient at focusing the minimal ...
The narwhal is a stocky cetacean with a relatively blunt snout, a large melon, and a shallow ridge in place of a dorsal fin. Males of this species have a large (1.5–3.0 m (4 ft 11 in – 9 ft 10 in)) long tusk , which is a protruding left canine thought to function as a weapon, a tool for feeding, in attracting mates or sensing water salinity.
A phylogenetic tree, phylogeny or evolutionary tree is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time. [ 1 ] [ 2 ] In other words, it is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon ...
A researcher fires a biopsy dart at an orca.The dart will remove a small piece of the whale's skin and bounce harmlessly off the animal. Cetology (from Greek κῆτος, kētos, "whale"; and -λογία, -logia) or whalelore (also known as whaleology) is the branch of marine mammal science that studies the approximately eighty species of whales, dolphins, and porpoises in the scientific ...
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.
They greatly affected cetacean evolution , because they spread across Earth's oceans. [7] They had long snouts, large eyes, and a nasal opening located farther up the head than in earlier archaeocetes — suggesting they could breathe with the head held horizontally, similar to modern cetaceans — a first step towards a blowhole.