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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.
This list currently includes only fossil genera and species. However, the Atlantic population of gray whales ( Eschrichtius robustus ) became extinct in the 18th century, and the baiji (or Chinese river dolphin, Lipotes vexillifer ) was declared " functionally extinct " after an expedition in late 2006 failed to find any in the Yangtze River .
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.
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 ...
Livyatan is an extinct genus of macroraptorial sperm whale containing one known species: L. melvillei.The genus name was inspired by the biblical sea monster Leviathan, and the species name by Herman Melville, the author of the famous novel Moby-Dick about a white bull sperm whale.
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.
Protocetus atavus ("first whale") is an extinct species of primitive cetacean from Egypt.It lived during the middle Eocene period 45 million years ago. The first discovered protocetid, Protocetus atavus was described by Fraas 1904 based on a cranium and a number of associated vertebrae and ribs found in middle Lutetian Tethyan marine limestone from Gebel Mokattam near Cairo, Egypt.
That is, the names are not capitalised except for the first word of a sentence and any proper names that are part of the common name. An example of the general use is bowhead whale. Examples of the inclusion of a proper name are North Pacific right whale (where "North Pacific" is a placename) and Bryde's whale (where Bryde was a person's name).