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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.
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 ]
Whales are fully aquatic, open-ocean animals: they can feed, mate, give birth, suckle and raise their young at sea. Whales range in size from the 2.6 metres (8.5 ft) and 135 kilograms (298 lb) dwarf sperm whale to the 29.9 metres (98 ft) and 190 tonnes (210 short tons) blue whale, which is the
Baleen whales range in size from the 6 m (20 ft) and 3,000 kg (6,600 lb) pygmy right whale to the 31 m (102 ft) and 190 t (210 short tons) blue whale, the largest known animal to have ever existed. [1] [2] They are sexually dimorphic.
The skull shares many characteristics with other sperm whales, and is comparable in size to that of the dwarf sperm whale. Like the modern Kogia, it probably hunted squid in the twilight zone, and frequented continental slopes. The environment it inhabited was likely a calm, nearshore area with a combination sandy and hard-rock seafloor.
Orcas also prey on larger species such as sperm whales, grey whales, humpback whales and minke whales. [ 84 ] [ 40 ] On three separate occasions in 2019 orcas were recorded to have killed blue whales off the south coast of Western Australia, including an estimated 18–22-meter (59–72 ft) individual. [ 89 ]
The smallest basilosaurid whale is Tutcetus and measures 8.2 ft (2.5 m) long. [34] The large size of basilosaurids is due to the extreme elongation of their lumbar vertebrae. They had a tail fluke, but their body proportions suggest that they swam by caudal undulation and that the fluke was not used for propulsion.
The pygmy right whale shares several characteristics with the right whales, with the exception of having a dorsal fin. Also, pygmy right whales' heads are no more than one quarter the size of their bodies, whereas the right whales' heads are about one-third the size of their bodies. [11] The pygmy right whale is the only extant member of its ...