Editing Whale (section)

==Taxonomy and evolution==
{{See also|List of cetaceans|List of extinct cetaceans}}

===Phylogeny===
The whales are part of the largely terrestrial mammalian [[clade]] [[Laurasiatheria]]. Whales [[paraphyletic|do not form a clade or order]]; the infraorder Cetacea includes [[dolphin]]s and [[porpoise]]s, which are not considered whales in the informal sense.{{Citation needed|date=November 2018}} The [[phylogenetic tree]] shows the relationships of whales and other mammals, with whale groups{{Citation needed|date=November 2018}} marked in green.

{{clade
|style=font-size:85%;line-height:85%
|label1=[[Laurasiatheria]]
|sublabel1={{circa|99&nbsp;[[MYA (unit)|Mya]]}}
|1={{clade
   |label1=[[Ferae]]
   |1=([[carnivorans]] and allies) [[File:Crocuta crocuta sideview.jpg|60 px]]
   |label2=[[Perissodactyla]]
   |2=([[horse]]s, [[rhino]]s, [[tapir]]s) [[File:Hartmann zebra hobatere S.jpg|60 px]]
   |label3=[[Artiodactyla]]
   |sublabel3={{circa|53&nbsp;[[MYA (unit)|Mya]]}}
   |3={{clade
      |label1=[[Tylopoda]]
      |1=([[camelid|camels, llamas]]) [[File:07. Camel Profile, near Silverton, NSW, 07.07.2007.jpg|45 px]]
      |label2=[[Artiofabula]]
      |2={{clade
         |1={{clade
            |label1=[[Suina]]
            |1=([[List of suines|pigs, hogs, peccaries]]) [[File:Scavenger feast - Yala December 2010 (1) (cropped).jpg|60 px]]
            |label2=[[Cetruminantia]]
            |2={{clade
               |label1=[[Ruminantia|Ruminants]]
               |1=([[cattle]], [[sheep]], [[antelope]]s) [[File:Walia ibex illustration white background.png|60 px]]
               |label2=[[Whippomorpha]]
               |2={{clade
                  |label1=[[Hippopotamidae]]
                  |1=([[Hippopotamidae|hippos]]) [[File:Hippopotamus amphibius in Tanzania 2830 Nevit.jpg|60 px]]
                  |label2=[[Cetacea]]
                  |2={{clade
                     |label1=<br/>
                     |sublabel1=<br/>
                     |1={{clade
                        |label1={{extinct}}[[Archaeocetes]]
                        |sublabel1=[[Archaeocetes|ancient whales]]&emsp;<br/>
                        |1=({{extinct}}''[[Ambulocetus]]'', {{extinct}}''[[Protocetus]]'', {{extinct}}''[[Basilosaurus]]'')
                        }}
                     |2={{clade
                        |label1=[[Mysticeti|<span style="color: green">Mysticeti</span>]]
                        |sublabel1=<span style="color: green">baleen whales</span>&emsp;<br/>
                        |1=([[right whale|<span style="color: green">right whales</span>]], [[gray whale|<span style="color: green">grey whales</span>]], [[rorqual|<span style="color: green">rorquals</span>]])
                        |label2=[[Odontoceti]]
                        |sublabel2=toothed whales
                        |2={{clade
                           |label1=[[Delphinoidea]]
                           |1=([[dolphin]]s, [[porpoise]]s, [[beluga whale|<span style="color: green">beluga whales</span>]], [[narwhal|<span style="color: green">narwhals</span>]])
                           |label2=[[Lipotoidea]]
                           |2=([[river dolphins]])
                           |label3=[[Physeteroidea|<span style="color: green">Physeteroidea</span>]]
                           |3=([[Physeteridae|<span style="color: green">sperm whales</span>]])
                           |label4=[[Ziphioidea|<span style="color: green">Ziphoidea</span>]]
                           |4=([[beaked whale|<span style="color: green">beaked whales</span>]])
                           }}
                        }}
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
}}

Cetaceans are divided into two parvorders. The larger parvorder, [[Mysticeti]] (baleen whales), is characterized by the presence of baleen, a sieve-like structure in the upper jaw made of [[keratin]], which it uses to filter [[plankton]], among others, from the water. [[Odontoceti|Odontocetes]] (toothed whales) are characterized by bearing sharp teeth for hunting, as opposed to their counterparts' baleen.{{sfn|Klinowska|1991|p=4}}

Cetaceans and [[artiodactyl]]s now are classified under the order [[Cetartiodactyla]], often still referred to as Artiodactyla, which includes both whales and [[hippopotamus]]es. The hippopotamus and pygmy hippopotamus are the whales' closest terrestrial living relatives.{{sfn|Gatesy|1997}}

===Mysticetes===
{{See also|Mysticeti}}
Mysticetes are also known as baleen whales. They have a pair of [[Blowhole (anatomy)|blowhole]]s side by side and lack teeth; instead they have [[baleen plates]] which form a sieve-like structure in the upper jaw made of keratin, which they use to filter [[plankton]] from the water. Some whales, such as the humpback, reside in the polar regions where they feed on a reliable source of schooling fish and [[krill]].{{sfn|Johnson|Wolman|1984}} These animals rely on their well-developed flippers and tail fin to propel themselves through the water; they swim by moving their fore-flippers and [[Caudal fin|tail fin]] up and down. Whale ribs loosely articulate with their [[thoracic vertebrae]] at the [[proximal]] end, but do not form a rigid rib cage. This adaptation allows the chest to compress during deep dives as the pressure increases.{{cn|date=April 2025}} Mysticetes consist of four families: [[Balaenopteridae|rorquals (balaenopterids)]], [[Cetotheriidae|cetotheriids]], [[Balaenidae|right whales (balaenids)]], and [[Eschrichtiidae|grey whales (eschrichtiids)]].

The main difference between each family of mysticete is in their feeding adaptations and subsequent behaviour.
Balaenopterids are the rorquals. These animals, along with the cetotheriids, rely on their throat pleats to gulp large amounts of water while feeding. The throat pleats extend from the mouth to the navel and allow the mouth to expand to a large volume for more efficient capture of the small animals they feed on. Balaenopterids consist of two genera and eight species.{{sfn|Goldbogen|2010}}
Balaenids are the right whales. These animals have very large heads, which can make up as much as 40% of their body mass, and much of the head is the mouth. This allows them to take in large amounts of water into their mouths, letting them feed more effectively.{{sfn|Froias|2012}}
Eschrichtiids have one living member: the grey whale. They are bottom feeders, mainly eating crustaceans and benthic invertebrates. They feed by turning on their sides and taking in water mixed with sediment, which is then expelled through the baleen, leaving their prey trapped inside. This is an efficient method of hunting, in which the whale has no major competitors.{{sfn|Jefferson et al.}}

===Odontocetes===
{{See also|Odontoceti}}

Odontocetes are known as toothed whales; they have teeth and only one blowhole. They rely on their well-developed sonar to find their way in the water. Toothed whales send out [[ultrasound|ultrasonic]] clicks using the [[melon (cetacean)|melon]]. Sound waves travel through the water. Upon striking an object in the water, the sound waves bounce back at the whale. These vibrations are received through fatty tissues in the jaw, which is then rerouted into the ear-bone and into the brain where the vibrations are interpreted.{{sfn|Jeanette et al.|1990|pp=203–427}} All toothed whales are opportunistic, meaning they will eat anything they can fit in their throat because they are unable to chew. These animals rely on their well-developed flippers and tail fin to propel themselves through the water; they swim by moving their fore-flippers and [[Caudal fin|tail fin]] up and down. Whale ribs loosely articulate with their [[thoracic vertebrae]] at the [[proximal]] end, but they do not form a rigid rib cage. This adaptation allows the chest to compress during deep dives as opposed to resisting the force of water pressure.{{cn|date=April 2025}} Excluding dolphins and porpoises, odontocetes consist of four families: [[Monodontidae|belugas and narwhals (monodontids)]], [[Physeteridae|sperm whales (physeterids)]], [[Kogiidae|dwarf and pygmy sperm whales (kogiids)]], and [[Ziphiidae|beaked whales (ziphiids)]].{{sfn|McBrearty|1991|pp=33–65}}

The differences between families of odontocetes include size, feeding adaptations and distribution. Monodontids consist of two species: the [[beluga whale|beluga]] and the [[narwhal]]. They both reside in the frigid arctic and both have large amounts of blubber. Belugas, being white, hunt in large pods near the surface and around pack ice, their coloration acting as camouflage. Narwhals, being black, hunt in large pods in the aphotic zone, but their underbelly still remains white to remain camouflaged when something is looking directly up or down at them. They have no dorsal fin to prevent collision with pack ice.{{sfn|Jefferson|2015a}}
Physeterids and Kogiids consist of [[sperm whale]]s. Sperm whales consist the largest and smallest odontocetes, and spend a large portion of their life hunting squid. ''P. macrocephalus'' spends most of its life in search of squid in the depths; these animals do not require any degree of light at all, in fact, blind sperm whales have been caught in perfect health. The behaviour of Kogiids remains largely unknown, but, due to their small lungs, they are thought to hunt in the [[photic zone]].{{sfn|Jefferson|2015b}}
Ziphiids consist of 22 species of [[beaked whale]]. These vary from size, to coloration, to distribution, but they all share a similar hunting style. They use a suction technique, aided by a pair of grooves on the underside of their head, not unlike the throat pleats on the [[rorqual]]s, to feed.{{sfn|Jefferson|2015c}}

As a formal clade (a group which does not exclude any descendant [[taxon]]), odontocetes also contains the [[porpoise]]s (Phocoenidae) and four or five living families of dolphins: oceanic dolphins ([[Delphinidae]]), [[South Asian river dolphin]]s ([[Platanistidae]]), the possibly extinct [[Yangtze River dolphin]] ([[Lipotidae]]), [[Inia|South American river dolphins]] ([[Iniidae]]), and [[La Plata dolphin]] (Pontoporiidae).

===Evolution===
{{Main|Evolution of cetaceans}}
[[File:Basilosaurus cetoides (1).jpg|right|thumb|[[Basilosaurus]] skeleton]]

Whales are descendants of land-dwelling mammals of the [[artiodactyl]] [[order (biology)|order]] (even-toed ungulates). They are related to the ''[[Indohyus]]'', an extinct [[chevrotain]]-like ungulate, from which they split approximately 48 million years ago.{{sfn|Northeastern Ohio Universities|2007}}{{sfn|Dawkins|2004}} Primitive cetaceans, or [[archaeocetes]], first took to the sea approximately 49 million years ago and became fully aquatic 5–10 million years later. What defines an archaeocete is the presence of anatomical features exclusive to cetaceans, alongside other primitive features not found in modern cetaceans, such as visible legs or asymmetrical teeth.{{sfn|Berkeley}}{{sfn|Thewissen et al.|2007}}{{sfn|Fahlke et al.|2011}}{{sfn|Gatesy|1997}} Their features became adapted for living in the [[Sea|marine environment]]. Major anatomical changes included their hearing set-up that channeled vibrations from the jaw to the earbone (''[[Ambulocetus]]'' 49 [[Mya (unit)|mya]]), a [[streamline (fluid dynamics)|streamlined]] body and the growth of flukes on the tail (''[[Protocetus]]'' 43 mya), the migration of the nostrils toward the top of the [[cranium]] ([[Blowhole (anatomy)|blowholes]]), and the modification of the forelimbs into flippers (''[[Basilosaurus]]'' 35 mya), and the shrinking and eventual disappearance of the hind limbs (the first odontocetes and mysticetes 34 mya).{{sfn|Kenneth|2001}}{{sfn|Bebej et al.|2012}}{{sfn|Reidenberg|2012|p=508}}

Whale morphology shows several examples of [[convergent evolution]], the most obvious being the streamlined fish-like body shape.{{sfn|Lam|1999}} Other examples include the use of [[Animal echolocation|echolocation]] for hunting in low light conditions&nbsp;— which is the same hearing adaptation used by [[bat]]s&nbsp;— and, in the rorqual whales, jaw adaptations, similar to those found in [[pelican]]s, that enable engulfment feeding.{{sfn|Moskowitz|2011}}

Today, the closest living relatives of cetaceans are the [[hippopotamus]]es; these share a [[Semiaquatic|semi-aquatic]] ancestor that branched off from other artiodactyls some 60 mya.{{sfn|Gatesy|1997}} Around 40 mya, a common ancestor between the two branched off into cetacea and [[anthracotheres]]; nearly all anthracotheres became extinct at the end of the Pleistocene 2.5 mya, eventually leaving only one surviving lineage&nbsp;– the hippopotamus.{{sfn|Boisserie|Lihoreau|Brunet|2005}}

Whales split into two separate parvorders around 34 mya&nbsp;– the baleen whales (Mysticetes) and the toothed whales (Odontocetes).{{sfn|PBS ''Nature''|2012}}{{sfn|Houben et al.|2013|pp=341–344}}{{sfn|Steeman et al.|2009|pp=573–585}}