Cetacea

The infraorder^[2] Cetacea /sɨˈteɪʃⁱə/ includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean 'whale'. Its original meaning, 'large sea animal', was more general. It comes from Ancient Greek κῆτος (kētos), used for whales and other huge fish or sea monsters. Cetology is the branch of marine science associated with the study of cetaceans. An ancient ancestor of the whale, Basilosaurus was thought to be a reptile until vestigial parts were recognized.^[3] Traditionally Cetacea was treated as an order, but it has become increasingly aware based on physiological data that cetaceans are not only a clade of even-toed ungulates, but that Cetacea might be recognized as an infraorder.^[2]

Fossil evidence suggests that the cetaceans share a common ancestor with hippopotamuses that began living in marine environments around 50 million years ago.^[4][5][6][7] Today, they are the mammals best adapted to aquatic life. The body of a cetacean is fusiform (spindle-shaped). The forelimbs are modified into flippers. The tiny hindlimbs are vestigial; they do not attach to the backbone and are hidden within the body. The tail has horizontal flukes. Cetaceans are nearly hairless, and are insulated from the cooler water they inhabit by a thick layer of blubber.

Some species are attributed with high levels of intelligence. At the 2012 meeting of the American Association for the Advancement of Science, support was reiterated for a cetacean bill of rights, listing cetaceans as non-human persons.^[8]

The collective noun "pod"^[9] is often used for a herd or school of marine mammals, especially a small herd or family group of whales or dolphins.

Physical characteristics

Respiration

Cetaceans breathe air, and surface periodically to exhale carbon dioxide and inhale a fresh supply of oxygen. During diving, a muscular action closes the blowholes (nostrils), which remain closed until the cetacean returns to the surface; when it surfaces, the muscles open the blowholes and warm air is exhaled.

Cetaceans' blowholes have evolved to a position at the top of the head, simplifying breathing in sometimes rough seas. When the stale air, warmed from the lungs, is exhaled, it condenses as it meets colder external air. As with a terrestrial mammal breathing out on a cold day, a small cloud of 'steam' appears. This is called the 'blow' or 'spout' and varies by species in terms of shape, angle, and height. Species can be identified at a distance using this characteristic.

Cetaceans can remain under water for much longer periods than most other mammals, (about seven to 120 minutes, varying by species) due to large physiological differences. Two studied advantages of cetacean physiology let this order (and other marine mammals) forage underwater for extended periods without breathing:

• Mammalian myoglobin concentrations in skeletal muscle have much variation. New Zealand white rabbits have 0.08 to 0.60% myoglobin by weight in wet muscle,^[10] whereas a northern bottlenose whale has 6.34 grams (0.224 oz) myoglobin per 100 grams wet muscle.^[11] Myoglobin, by nature, has a higher oxygen affinity than hemoglobin. The higher the myoglobin concentration in skeletal muscle, the longer the animal can stay underwater.
• Increased body size also increases maximum dive duration. Greater body size implies increased muscle mass and increased oxygen stores. Cetaceans also obey Kleiber's law, which states that mass and metabolic rate are inversely related, i.e., larger animals consume less oxygen than smaller animals per unit mass.

Vision, hearing and echolocation

Cetacean eyes are set on the sides rather than the front of the head. This means only cetaceans 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 light that reaches deep water. Cetaceans make up for their generally poor vision (with the exception of the dolphin) with excellent hearing.

The external ear of cetaceans has lost the pinna (visible ear), but still retains an extremely narrow external auditory meatus. To register sounds, instead, the posterior part of the mandible has a thin lateral wall (the pan bone) behind which a concavity houses a large fat pad. The fat pad passes anteriorly into the greatly enlarged mandibular foramen to reach in under the teeth, and posteriorly to reach the thin lateral wall of the ectotympanic. The ectotympanic only offers a reduced attachment area for the tympanic membrane and the connection between this auditory complex and the rest of the skull is reduced in cetaceans — to a single, small cartilage in oceanic dolphins. In odontocetes, the complex is surrounded by spongy tissue filled with air spaces, while in mysticetes it is integrated into the skull similar to land mammals. In odontocetes, the tympanic membrane (or ligament) has the shape of a folded-in umbrella that stretches from the ectotympanic ring and narrows off to the malleus (quite unlike the flat, circular membrane found in land mammals.) In mysticetes, it also forms a large protrusion (known as the "glove finger"), which stretches into the external meatus, and the stapes are larger than in odontocetes. In some small sperm whales, the malleus is fused with the ectotympanic. The ear ossicles are pachyosteosclerotic (dense and compact) in cetaceans and very different in shape compared to land mammals (other aquatic mammals, such as sirenians and earless seals, have also lost their pinnae). In modern cetaceans, the semicircular canals are much smaller relative to body size than in other mammals.^[12]

In modern cetaceans, the auditory bulla is separated from the skull and composed of two compact and dense bones (the periotic and tympanic) referred to as the tympano-periotic complex. This complex is located in a cavity in the middle ear, which, in Mysticeti, is divided by a bony projection and compressed between the exoccipital and squamosal but, in Odontoceti, is large and completely surrounds the bulla (hence called "peribullar"), which is therefore not connected to the skull except in physeterids. In odontoceti, the cavity is filled with a dense foam in which the bulla hangs suspended in five or more sets of ligaments. The pterygoid and peribullar sinuses that form the cavity tend to be more developed in shallow water and riverine species than in pelagic mysticeti. In odontoceti, the composite auditory structure is thought to serve as an acoustic isolator, analogous to the lamellar construction found in the temporal bone in bats.^[13]

Odontoceti (toothed whales, which includes dolphins and porpoises) are generally capable of echolocation.^[14] From this, Odontoceti can discern the size, shape, surface characteristics, distance and movement of an object. With this ability, cetaceans can search for, chase and catch fast-swimming prey in total darkness.^[15] Echolocation is so advanced in most Odontoceti, they can distinguish between prey and nonprey (such as humans or boats); captive Odontoceti can be trained to distinguish between, for example, balls of different sizes or shapes. Mysticeti (baleen whales) have exceptionally thin, wide basilar membranes in their cochleae without stiffening agents, making their ears adapted for processing low to infrasonic frequencies.^[16]

Cetaceans also use sound to communicate, whether it be groans, moans, whistles, clicks, or the complex 'singing' of the humpback whale. Besides hearing and vision, at least one species, the tucuxi or Guiana dolphin, is able to use electroreception to sense prey.^[17]

Tails

All cetaceans have tails containing (or known as) flukes. These lobes are horizontally oriented and the tail moves up and down, unlike fish tails. The feature evolved by the time of basilosauridae and dorudontinae.

Feeding

The toothed whales, such as the sperm whale, beluga, dolphins, and porpoises, have teeth for catching fish, squid or other marine life. When a killer whales catch a seal, they bite off and swallow one chunk at a time.

Instead of teeth, the Mysticeti (Baleen whale) have baleen plates made of keratin (the same substance as human fingernails), which hang from the upper jaw. These plates filter small animals (such as krill and fish) from the seawater. Not all Mysticeti feed on plankton.

The larger Cetaceans, like the blue, humpback, bowhead, and minke whales, eat small shoaling fish, such as herring and sardines, called micronecton. The gray whale (Eschrichtius robustus), is a benthic feeder, primarily eating sea-floor crustaceans. Instead of preying on few species, Beluga whales are opportunistic feeders. They prey on about 100 different kinds of primarily bottom-dwelling animals. They eat octopus, squid, crabs, snails, sandworms, and fishes such as capelin, cod, herring, smelt, and flounder.

In terms of food intake, a blue whale eats up to 3,600 kg (8,000 lb) of krill each day for about 120 days while it is estimated to take 1,000 kg (2,200 lb) of food to fill a blue whale's stomach. Gray whales eat about 150,000 kg (340,000 lb) of food during a 130 to 140 day feeding period - a daily average intake of about 1,089 kg (2,400 lb.). It is estimated to take 300 kg (660 lb.) of food to fill a gray whale's stomach. Gray whales gain about 16% to 30% of their total body weight during a feeding season.^[18]

Sexual Reproduction

Cetaceans evolved from land-dwelling ancestors and lost external hind limbs. They evolved significantly reduced pelvic bones that seemed to serve no other function except to anchor muscles that maneuver the penis. Cetacean pelvic bones are unique because they are no longer constrained by sacral and hind limb attachments or by hind limb locomotion.^[19]

Cetacean pelvic bones were often thought of as “useless vestiges” of their land-dwelling ancestors.^[20] However, they are a critical component of male reproductive fitness.

The paired pelvic bones anchor the genitalia and the paired ischiocavernosus muscles that control the penis.^[21][22] In male cetaceans, the paired ischiocavernosus muscles insert deeply toward the distal end of the penis, while proximally encapsulating the paired crus of the penis that anchor to each pelvic bone.^[23][24] The ischiocavernosus muscles appear to maneuver the penis by pulling it to one side or the other^[25] and may also maintain erection by compressing the corpus cavernosusm proximally.^[26] The ischiocavernosus muscles may work in coordination with other soft tissue innovacations to control the penis, which suggests the importance of ischiocavernosus muscles in penis movement.

Both size and shape of pelvic bones are evolutionary correlated to relative testes mass, which is a strong indication of postcopulatory sexual selection.^[27][28] Male cetacean with relatively intense sexual selection tend to evolve larger penises and pelvic bones compared to their body length. The relative size of pelvic bones increases with relative testes mass. With PGLS (Phlogenetic generalized least squares) methodology, relative pelvic size was positively correlated with relative testes mass (phylogenetically controlled, P = 0.0006, r = 0.55), a pattern not observed in ribs.^[19] Sexual Selection also appears to favor divergence in shape. Pelvic bone shape diverges more rapidly among species that have diverged in inferred mating system. According to analysis on pelvic and rib bones, pelvic bone shape divergence (independent of size) was positively correlated (Pearson’s correlation P = 0.003, r = 0.82). However such a relationship did not help explaining rib bones (Pearson’s correlation P = 0.98, r = -0.009).^[19]

Taxonomy

Cetacea contains about 90 species, all marine except for four species of freshwater dolphins. Cetaceans can be divided into two further groups: Mysticeti (baleen whales) and Odontoceti (toothed whales, which includes dolphins, porpoises, and the Sperm Whale). The species range in size from Commerson's dolphin, smaller than a human, to the blue whale, the largest animal ever known to have lived.

Traditionally Cetacea was recognized as a unique order of mammals. However based on the molecular research and recent fossil discoveries show that cetaceans are nested within an other order of mammals, Artiodactyla, with a close relationship with the family Hippopotamidae^{[4][5][6][7][29][30][31][32][33][34]} At least one author believes that Cetacea should be best recognized as an infraorder in the suborder Whippomorpha in Artiodactyla.^[2]

Artiodactyla	Tylopoda    Artiofabula     Suina        Cetruminantia     Ruminantia    Whippomorpha     Hippopotamidae  Cetacea

Mammalian characteristics include warm-bloodedness, breathing air through their lungs, suckling their young, and growing hair, although in the case of cetaceans, very little of it.

Another way of distinguishing a cetacean from a fish is the shape and orientation of the tail. Fish tails are vertical and move from side to side when the fish swims. A cetacean's tail — called a fluke — is horizontal and moves up and down, because cetacean spines bend in the same manner as a human spine.

Evolution

Cetacean (whales, dolphins and porpoises) evolution has one of the most complete fossil records, which makes tracking the intermediates between families easier. They are marine mammal relatives of the artiodactyl family Raoellidae, a group of land mammals characterized by an even-toed ungulate skull, slim limbs, and an ear with significant similarities to that of early whales.^[35] One of these in particular, Indohyus, was characterized by a long snout and osteosclerosis, the second of which suggests that "Indohyus" was aquatic.^[36] The terrestrial origins of cetaceans are indicated first by their need to breathe air from the surface, the bones of their fins, which resemble the limbs of land mammals, and by the vestigial remains of hind legs inherited from their four-legged ancestors. Loss of external hind limbs is particularly well documented and had been investigated to further explore the evolution of the families Pakicetidae, Ambulocetidae, Remingtonocetidae, Protocetidae, and Basilosauridae.

The question of how land animals became ocean-going was a mystery until discoveries starting in the late 1970s in Pakistan revealed several stages in the transition of cetaceans from land to sea:^[37]

This image does not capture the true phylogenetic evolution of a particular species, but it is an illustrative representation of the evolution of cetaceans from terrestrial four-legged mammals, from their probable ancestor, through different stages of adaptation to aquatic life to modern cetaceans type, hydrodynamic body shape, fully developed caudal fin and vestigial hind legs. Although Pakicetidae still had weight supporting hind limbs, they are considered to be the first cetaceans and are not included in Artiodactylia.^[38] This gave rise to Ambulocetidae whose strong tail suggested a life of more swimming.^[39] Remingtonocetidae remained able to support its own weight but also developed a strong base for foot-powered swimming.^[40] Protoceids were the first cetaceans to be found all over the world instead of simply Pakistan and India indicating more advanced aquatic locomotion. Two main genera are known: "Artiocetus" and "Georgiacetus." The first had reduced hind limbs but was still able to bear weight, while "Georgiacetus" had a pelvis which was completely disconnected from the spine, meaning it could not support its own weight and thus spent all of its time in water.^[36] Basilosauridae were the first fully aquatic cetaceans. There were two main types, "Basilosaurus" and dorudontids. Both were characterized by tiny hind limbs, tail flukes, and an elongated vertebral column. This provided the foundation for the modern cetaceans mysticeti and odontoceti, respectively the suborders of baleen whales and toothed whales, a separation that occurred during the Oligocene (Janjucetus and Squalodon represent the early forms of their suborders).

Mysticeti vs Odontoceti

Fossils indicate, before evolving baleen, the Mysticeti also had teeth, so defining the Odontoceti by teeth alone is problematic. Instead, paleontologists have identified other features uniting fossil and modern odontocetes that are not shared by Mysticeti. It was also assumed that toothed whales evolved their asymmetrical skulls as an adaptation to their echolocation, but newer discoveries indicate the common ancestor of the present whales actually had a contorted skull, as well. Cranial asymmetry is now known to have evolved in ancient whales as part of a set of traits linked to directional hearing, including pan-bone thinning of the lower jaws, the development of mandibular fat pads, and the isolation of the ear region.^[41] This likely means, while the asymmetry in the Odontoceti skull has increased over time, the Mysticeti skull has evolved from asymmetrical to symmetrical.^[42]

Characteristic	Odontoceti	Mysticeti
Feeding	Echolocation, fast	Filter feeder, not fast
Size	Smaller (except Sperm whale and beaked whale)	Larger (except pygmy right whale)
Blowhole	One	Two
Dentition	Teeth	Baleen plates
Melon	Ovoid, in anterior facial region	Vestigial or none
Skull and facial tissue	Dorsally asymmetric	Symmetric
Sexual dimorphism	Some species have larger males	Females always larger
Mandible	Symphyseal (fused anteriorly)	Nonsymphyseal
Pan bone of lower jaw	Yes	No
Maxillae projection	Outward over expanded supraorbital processes	Under eye orbit, with bony protuberance anterior to eye orbit
Olfactory nerve and bulb	Absent[43]	Vestigial[44]
Periotic bone	External to skull, fused with tympanic bulla	Fused with skull[45]

Classification

The classification here closely follows Dale W. Rice, Marine Mammals of the World: Systematics and Distribution (1998), which has become the standard taxonomy reference in the field. There is very close agreement between this classification and that of Mammal Species of the World: 3rd Edition (Wilson and Reeder eds., 2005). Any differences are noted using the abbreviations "Rice"^[46] and "MSW3"^[1] respectively. Further differences due to recent discoveries are also noted.

Discussion of synonyms and subspecies are relegated to the relevant genus and species articles.

• ORDER CETACEA
  • Suborder Mysticeti: Baleen whales
    • Family Balaenidae: Right whales and bowhead whale
      • Genus Balaena
        • Bowhead whale, Balaena mysticetus
      • Genus Eubalaena – Rice considered the three right whales as subspecies of Balaena glacialis
        • North Atlantic right whale, Eubalaena glacialis
        • North Pacific right whale, Eubalaena japonica
        • Southern right whale, Eubalaena australis
    • Family Balaenopteridae: Rorquals
      • Subfamily Balaenopterinae
        • Genus Balaenoptera
          • Common minke whale, Balaenoptera acutorostrata
          • Antarctic minke whale, Balaenoptera bonaerensis
          • Sei whale, Balaenoptera borealis
          • Bryde's whale, Balaenoptera brydei
          • Eden's whale Balaenoptera edeni – Rice lists this as a separate species, MSW3 does not
          • Omura's whale – Balaenoptera omurai - MSW3 lists this is a synonym of Bryde's whale but suggests this may be temporary.
          • Blue whale, Balaenoptera musculus
          • Fin whale, Balaenoptera physalus
      • Subfamily Megapterinae
        • Genus Megaptera
          • Humpback whale, Megaptera novaeangliae
    • Family Eschrichtiidae
      • Genus Eschrichtius
        • Gray whale, Eschrichtius robustus
    • Family Cetotheriidae
      • Genus Caperea
        • Pygmy right whale, Caperea marginata
  • Suborder Odontoceti: toothed whales
    • Family Delphinidae: Dolphin
      • Genus Cephalorhynchus
        • Commerson's dolphin, Cephalorhyncus commersonii
        • Chilean dolphin, Cephalorhyncus eutropia
        • Heaviside's dolphin, Cephalorhyncus heavisidii
        • Hector's dolphin, Cephalorhyncus hectori
      • Genus Delphinus
        • Long-beaked common dolphin, Delphinus capensis
        • Short-beaked common dolphin, Delphinus delphis
        • Arabian common dolphin, Delphinus tropicalis. Rice recognises this as a separate species. MSW3 does not.
      • Genus Feresa
        • Pygmy killer whale, Feresa attenuata
      • Genus Globicephala
        • Short-finned pilot whale, Globicephala macrorhyncus
        • Long-finned pilot whale, Globicephala melas
      • Genus Grampus
        • Risso's dolphin, Grampus griseus
      • Genus Lagenodelphis
        • Fraser's dolphin, Lagenodelphis hosei
      • Genus Lagenorhynchus
        • Atlantic white-sided dolphin, Lagenorhynchus acutus
        • White-beaked dolphin, Lagenorhynchus albirostris
        • Peale's dolphin, Lagenorhynchus australis
        • Hourglass dolphin, Lagenorhynchus cruciger
        • Pacific white-sided dolphin, Lagenorhynchus obliquidens
        • Dusky dolphin, Lagenorhynchus obscurus
      • Genus Lissodelphis
        • Northern right whale dolphin, Lissodelphis borealis
        • Southern right whale dolphin, Lissodelphis peronii
      • Genus Orcaella
        • Irrawaddy dolphin, Orcaella brevirostris
          • Australian snubfin dolphin, Orcaella heinsohni A 2005 discovery, thus it is not recognized by Rice or MSW3 and subject to revision.
      • Genus Orcinus
        • Killer whale, Orcinus orca
      • Genus Peponocephala
        • Melon-headed whale, Peponocephala electra
      • Genus Pseudorca
        • False killer whale, Pseudorca crassidens
      • Genus Sotalia
        • Tucuxi, Sotalia fluviatilis, see the species article for a discussion
        • Costero, Sotalia guianensis, see the species article for a discussion
      • Genus Sousa
        • Pacific humpback dolphin, Sousa chinensis
        • Indian humpback dolphin, Sousa plumbea
        • Atlantic humpback dolphin, Sousa teuszii
      • Genus Stenella
        • Pantropical spotted dolphin, Stenella attenuata
        • Clymene dolphin, Stenella clymene
        • Striped dolphin, Stenella coeruleoalba
        • Atlantic spotted dolphin, Stenella frontalis
        • Spinner dolphin, Stenella longirostris
      • Genus Steno
        • Rough-toothed dolphin, Steno bredanensis
      • Genus Tursiops – Rice and MSW3 tentatively agree on this classification
        • Indian Ocean bottlenose dolphin, Tursiops aduncus
        • Burrunan dolphin, Tursiops australis
        • Common bottlenose dolphin, Tursiops truncatus
    • Family Monodontidae
      • Genus Delphinapterus
        • Beluga, Delphinapterus leucas
      • Genus Monodon
        • Narwhal, Monodon monoceros
    • Family Phocoenidae: Porpoises
      • Genus Neophocaena
        • Finless porpoise, Neophocaena phocaenoides
      • Genus Phocoena
        • Spectacled porpoise, Phocoena dioptrica
        • Harbour porpoise, Phocoena phocaena
        • Vaquita, Phocoena sinus
        • Burmeister's porpoise, Phocoena spinipinnis
      • Genus Phocoenoides
        • Dall's porpoise, Phocoenoides dalli
    • Family Physeteridae: Sperm whale family
      • Genus Physeter
        • Sperm whale, Physeter catodon (syn. P. macrocephalus)
    • Family Kogiidae – MSW3 treats Kogia as a member of Physeteridae
      • Genus Kogia
        • Pygmy sperm whale, Kogia breviceps
        • Dwarf sperm whale, Kogia sima
    • Superfamily Platanistoidea: River dolphins
      • Family Iniidae
        • Genus Inia
          • Amazon river dolphin, Inia geoffrensis
          • Bolivian river dolphin, Inia boliviensis (considered a sub-species of I. geoffrensis by much of the scientific community)
          • Araguaian river dolphin. Inia araguaiaensis. A 2014 discovery, thus it is not recognized by Rice or MSW3 and subject to revision.
      • Family Lipotidae – MSW3 treats Lipotes as a member of Iniidae
        • Genus Lipotes
          • Baiji, Lipotes vexillifer
      • Family Pontoporiidae – MSW3 treats Pontoporia as a member of Iniidae
        • Genus Pontoporia
          • La Plata dolphin, Pontoporia blainvillei
      • Family Platanistidae
        • Genus Platanista
          • South Asian river dolphin, Platanista gangetica. MSW3 treats Platanista minor as a separate species, with common names Ganges River dolphin and Indus River dolphin, respectively.
    • Superfamily Ziphioidea: Beaked whales
      • Family Ziphidae,
        • Genus Berardius
          • Arnoux's beaked whale, Berardius arnuxii
          • Baird's beaked whale (North Pacific bottlenose whale), Berardius bairdii
        • Subfamily Hyperoodontidae
          • Genus Hyperoodon
            • Northern bottlenose whale, Hyperoodon ampullatus
            • Southern bottlenose whale, Hyperoodon planifrons
          • Genus Indopacetus
            • Indo-Pacific beaked whale (Longman's beaked whale), Indopacetus pacificus
          • Genus Mesoplodon, Mesoplodont whale
            • Sowerby's beaked whale, Mesoplodon bidens
            • Andrews' beaked whale, Mesoplodon bowdoini
            • Hubbs' beaked whale, Mesoplodon carlhubbsi
            • Blainville's beaked whale, Mesoplodon densirostris
            • Gervais' beaked whale, Mesoplodon europaeus
            • Ginkgo-toothed beaked whale, Mesoplodon ginkgodens
            • Gray's beaked whale, Mesoplodon grayi
            • Hector's beaked whale, Mesoplodon hectori
            • Strap-toothed whale, Mesoplodon layardii
            • True's beaked whale, Mesoplodon mirus
            • Perrin's beaked whale, Mesoplodon perrini, recognized in 2002 and as such is listed by MSW3 but not Rice.
            • Pygmy beaked whale, Mesoplodon peruvianus
            • Stejneger's beaked whale, Mesoplodon stejnegeri
            • Spade-toothed whale, Mesoplodon traversii
            • Deraniyagala's beaked whale, Mesoplodon hotaula, recognized in 2014
        • Genus Tasmacetus
          • Shepherd's beaked whale, Tasmacetus shepherdi
        • Genus Ziphius
          • Cuvier's beaked whale, Ziphius cavirostris

†Recently extinct

See also

• List of cetaceans by population
• Unihemispheric slow-wave sleep

References

External links

Wikispecies has information related to: Cetacea

Wikimedia Commons has media related to Cetacea.

The Wikibook Dichotomous Key has a page on the topic of: Cetacea

Look up Cetacea in Wiktionary, the free dictionary.

• "Cetaceans". Encyclopedia of Earth. Retrieved February 2011. 
• Scottish Cetacean Research & Rescue – see page on Taxonomy
• "Dolphin and Whale News". Science Daily. Retrieved March 2010. 
• Futuyma, Douglas J. (1998). "Cetacea Evolution". Retrieved 2010. 
• EIA Cetacean campaign: Reports and latest info.
• EIA in USA: reports etc.

Extant mammal orders by infraclass Kingdom Animalia Phylum Chordata Subphylum Vertebrata (unranked) Amniota Yinotheria Australosphenida Monotremata (Platypus and echidnas) Metatheria (Marsupial inclusive) Ameridelphia Paucituberculata (Shrew opossums) Didelphimorphia (Opossums) Australidelphia Microbiotheria (Monito del Monte) Notoryctemorphia (Marsupial moles) Dasyuromorphia (Quolls and dunnarts) Peramelemorphia (Bilbies and bandicoots) Diprotodontia (Kangaroos and relatives) Eutheria (Placental inclusive) Xenarthra Cingulata (Armadillos) Pilosa (Anteaters and sloths) Afrotheria Afrosoricida (Tenrecs and golden moles) Macroscelidea (Elephant shrews) Tubulidentata (Aardvark) Hyracoidea (Hyraxes) Proboscidea (Elephants) Sirenia (Dugongs and manatees) Boreoeutheria Laurasiatheria Soricomorpha (Shrews and moles) Erinaceomorpha (Hedgehogs and relatives) Chiroptera (Bats) Pholidota (Pangolins) Carnivora Perissodactyla (Odd-toed ungulates) Artiodactyla (Even-toed ungulates) Cetacea (Whales and dolphins) Euarchontoglires Rodentia (Rodents) Lagomorpha (Rabbits and relatives) Scandentia (Treeshrews) Dermoptera (Colugos) Primates

Extant Cetacea species Kingdom Animalia Phylum Chordata Class Mammalia Infraclass Eutheria Superorder Laurasiatheria (unranked) Cetartiodactyla (unranked) Whippomorpha   Suborder Mysticeti (Baleen whales) Balaenidae Balaena Bowhead whale (B. mysticetus) Eubalaena (Right whales) Southern right whale (E. australis) North Atlantic right whale (E. glacialis) North Pacific right whale (E. japonica) Balaenopteridae (Rorquals) Balaenoptera Common minke whale (B. acutorostrata) Antarctic minke whale (B. bonaerensis) Sei whale (B. borealis) Bryde's whale (B. brydei) Pygmy Bryde's whale (B. edeni) Blue whale (B. musculus) Omura's whale (B. omurai) Fin whale (B. physalus) Megaptera Humpback whale (M. novaeangliae) Eschrichtiidae Eschrichtius Gray whale (E. robustus) Neobalaenidae Caperea Pygmy right whale (C. marginata)   Suborder Odontoceti (Toothed whales) (cont. below) Delphinidae (Oceanic dolphins) Cephalorhynchus Commerson's dolphin (C. commersonii) Chilean dolphin (C. eutropia) Haviside's dolphin (C. heavisidii) Hector's dolphin (C. hectori) Delphinus Long-beaked common dolphin (D. capensis) Short-beaked common dolphin (D. delphis) Feresa Pygmy killer whale (F. attenuata) Globicephala (Pilot whales) Short-finned pilot whale (G. macrorhynchus) Long-finned pilot whale (G. melas) Grampus Risso's dolphin (G. griseus) Lagenodelphis Fraser's dolphin (L. hosei) Lagenorhynchus Atlantic white-sided dolphin (L. acutus) White-beaked dolphin (L. albirostris) Peale's dolphin (L. australis) Hourglass dolphin (L. cruciger) Pacific white-sided dolphin (L. obliquidens) Dusky dolphin (L. obscurus) Lissodelphis (Right whale dolphins) Northern right whale dolphin (L. borealis) Southern right whale dolphin (L. peronii) Orcaella Irrawaddy dolphin (O. brevirostris) Australian snubfin dolphin (O. heinsohni) Orcinus Killer whale (O. orca) Peponocephala Melon-headed whale (P. electra) Pseudorca False killer whale (P. crassidens) Sotalia Tucuxi (S. fluviatilis) Costero (S. guianensis) Sousa Indo-Pacific humpback dolphin (S. chinensis) Atlantic humpback dolphin (S. teuszii) Stenella Pantropical spotted dolphin (S. attenuata) Clymene dolphin (S. clymene) Striped dolphin (S. coeruleoalba) Atlantic spotted dolphin (S. frontalis) Spinner dolphin (S. longirostris) Steno Rough-toothed dolphin (S. bredanensis) Tursiops Indo-Pacific bottlenose dolphin (T. aduncus) Burrunan dolphin (T. australis) Common bottlenose dolphin (T. truncatus)   Suborder Odontoceti (Toothed whales) (cont. above) Monodontidae Delphinapterus Beluga (D. leucas) Monodon Narwhal (M. monoceros) Phocoenidae (Porpoises) Neophocaena Finless porpoise (N. phocaeniodes) Phocoena Spectacled porpoise (P. dioptrica) Harbor porpoise (P. phocoena) Vaquita (P. sinus) Burmeister's porpoise (P. spinipinnis) Phocoenoides Dall's porpoise (P. dalli) Physeteridae Physeter Sperm whale (P. macrocephalus) Kogiidae Kogia Pygmy sperm whale (K. breviceps) Dwarf sperm whale (K. simus) Iniidae Inia Amazon river dolphin (I. geoffrensis) Lipotidae Lipotes Baiji (L. vexillifer) Platanistidae Platanista Ganges and Indus River dolphin (P. gangetica) Pontoporiidae Pontoporia La Plata dolphin (P. blainvillei) Ziphiidae (Beaked whales) Berardius Arnoux's beaked whale (B. arnuxii) Baird's beaked whale (B. bairdii) Hyperoodon Northern bottlenose whale (H. ampullatus) Southern bottlenose whale (H. planifrons) Indopacetus Tropical bottlenose whale (I. pacificus) Mesoplodon (Mesoplodont whales) Sowerby's beaked whale (M. bidens) Andrews' beaked whale (M. bowdoini) Hubbs' beaked whale (M. carlhubbsi) Blainville's beaked whale (M. densirostris) Gervais' beaked whale (M. europaeus) Ginkgo-toothed beaked whale (M. ginkgodens) Gray's beaked whale (M. grayi) Hector's beaked whale (M. hectori) Strap-toothed whale (M. layardii) True's beaked whale (M. mirus) Perrin's beaked whale (M. perrini) Pygmy beaked whale (M. peruvianus) Stejneger's beaked whale (M. stejnegeri) Spade-toothed whale (M. traversii) Tasmacetus Shepherd's beaked whale (T. sheperdi) Ziphius Cuvier's beaked whale (Z. cavirostris)