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The order Artiodactyla consists of 349 extant species belonging to 132 genera. This does not include hybrid species or extinct prehistoric species. Modern molecular studies indicate that the 132 genera can be grouped into 23 families; these families are grouped into named suborders and many are further grouped into named clades, and some of these families are subdivided into named subfamilies.
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]
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 sperm whale or cachalot (Physeter macrocephalus) is the largest of the toothed whales and the largest toothed predator.It is the only living member of the genus Physeter and one of three extant species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia.
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.
Andrewsarchus (/ ˌ æ n d r uː ˈ s ɑːr k ə s /), meaning "Andrews' ruler", is an extinct genus of artiodactyl that lived during the Middle Eocene in what is now China. The genus was first described by Henry Fairfield Osborn in 1924 with the type species A. mongoliensis based on a largely complete cranium.
The largest known basilosaurid, Perucetus colossus, is believed to be even bigger, with a length of about 17–20 metres (56–66 ft) and possibly comparable to, if not larger than, the modern blue whale in terms of weight, [15] though other researchers argue that it was much lighter.
If the upper size estimates for Bruhathkayosaurus are accurate, it would even rival the size of the largest recorded blue whale. Mature blue whales can reach 30 m (98 ft) in length, and the record-holder blue whale was recorded at 173 tonnes (190 short tons), [23] with estimates of up to 199 tonnes (220 short tons). [24]