Odontocetes

The odontocetes (Odontoceti) comprise all the cetaceans that have teeth and an echolocation system. Unlike the mysticetes, they have no baleen: they hunt individual prey (fish, squid, sometimes other marine mammals) which they locate with a biosonar. This suborder brings together the dolphins, the killer whales, the porpoises, the sperm whales, the beaked whales and the river dolphins. According to the reference list of the Society for Marine Mammalogy (SMM, Committee on Taxonomy), which is regularly updated, there are about 79 living odontocete species, out of a total of about 94 living cetacean species, 15 of them mysticetes, spread across 10 families.

This page sets out an inventory structured by family and faithful to that reference list. It flags the disputed taxonomic points (synonymies, recent splits) explicitly rather than settling them arbitrarily.

Family Delphinidae, the oceanic dolphins (19 genera, 38 species)

The Delphinidae are by far the richest family of the suborder, with 38 species in 19 genera. It includes the small dolphins as well as the killer whale and the pilot whales, taxonomically “dolphins”. The list below follows the Society for Marine Mammalogy in its current version, which has endorsed the revision by Galatius et al. (2025) reorganising the genus Lagenorhynchus.

Points under debate. The “long-beaked” common dolphin (formerly Delphinus capensis) is no longer a distinct species: the Society for Marine Mammalogy placed it in synonymy with Delphinus delphis as early as 2016; a possible reinstatement in the north-east Pacific (D. delphis bairdii) remains at subspecies level. The revision by Galatius et al. (2025), now followed by the SMM, has broken up the genus Lagenorhynchus, long recognised as polyphyletic: only the white-beaked dolphin (L. albirostris) remains in it; the Atlantic white-sided dolphin moves into Leucopleurus, the Pacific white-sided and dusky dolphins into the new genus Aethalodelphis, while Peale’s and hourglass dolphins join Cephalorhynchus. This new arrangement, adopted here, has not yet been taken up by every database. Tamanend’s bottlenose dolphin (Tursiops erebennus), recently reinstated as a distinct species, and the killer whale are also under discussion: the SMM now recognises three killer whale subspecies, O. o. ater (“resident”), O. o. rectipinnus (“Bigg’s” or “transient”) and O. o. orca (the nominate form), whose elevation to the rank of distinct species is debated but not yet accepted.

Family Phocoenidae, the porpoises (3 genera, 7 species)

The vaquita (Phocoena sinus), endemic to the northern Gulf of California, is the most threatened cetacean in the world: the IUCN lists it as “Critically Endangered”, with an estimated population of about ten individuals, a victim of illegal gillnets.

Family Monodontidae, narwhal and beluga (2 genera, 2 species)

Family Ziphiidae, the beaked whales (6 genera, 24 species)

The second most diverse family of the odontocetes with 24 species, the Ziphiidae are deep divers that remain poorly known; several species have never been reliably observed alive. The genus Mesoplodon alone accounts for 16 species.

Family Physeteridae, the sperm whale (1 genus, 1 species)

Family Kogiidae, pygmy and dwarf sperm whales (1 genus, 2 species)

Family Platanistidae, the Asian river dolphins (1 genus, 2 species)

Point under debate. The recognition of two distinct Platanista species, the Ganges river dolphin (P. gangetica) and the Indus river dolphin (P. minor), is adopted here but remains under discussion: some authorities still treat the Indus river dolphin as a subspecies (P. gangetica minor) rather than as a species in its own right.

Family Iniidae, the Amazonian boto (1 genus, 1 species)

Point under debate. A second species, Inia araguaiaensis (the Araguaian river dolphin), was proposed in 2014, but it is not recognised by the Committee on Taxonomy of the SMM, for want of consensus; we therefore mention it as a proposed taxon, not a validated one. Likewise, the position of Inia and Pontoporia, as separate families (adopted here) or grouped into an enlarged Iniidae, varies between authors.

Family Lipotidae, the baiji (1 genus, 1 species)

  • Lipotes vexillifer, baiji, Yangtze river dolphin

The baiji is still carried on the SMM reference list among the 79 odontocetes, but the IUCN lists it as “Critically Endangered (Possibly Extinct)”: its last confirmed sighting dates from 2002 and a 2006 expedition detected no individuals. It has not, however, been officially declared extinct. It is a stark illustration of how vulnerable river dolphins are to the engineering of rivers.

Family Pontoporiidae, the La Plata dolphin (1 genus, 1 species)

Taxonomic summary of the odontocetes

FamilyGeneraSpecies
Delphinidae1938
Ziphiidae624
Phocoenidae37
Monodontidae22
Kogiidae12
Platanistidae12
Physeteridae11
Iniidae11
Lipotidae11
Pontoporiidae11
Total36 genera≈ 79 species
Counts follow the List of Marine Mammal Species and Subspecies of the Society for Marine Mammalogy (Committee on Taxonomy), in its current, regularly updated version.

Characteristics of the odontocetes

Odontocetes differ from mysticetes in a set of traits tied to active predation and to echolocation. They are recognised in particular by their single blowhole (against two in mysticetes) and by their asymmetrical skull, shaped by the sound-producing apparatus. For a comparative overview, see our page on the differences between whale, sperm whale and dolphin.

A dentition adapted to seizing prey, sometimes reduced

Most odontocetes have functional conical teeth, from 2 to more than 200 depending on the species, which serve to seize prey and not to chew it. The dentition is generally homodont (all the teeth have a similar shape). Some lineages are exceptions: in the beaked whales (Ziphiidae) the teeth are vestigial; females and juveniles often have none showing, and only males erupt one or two pairs of “tusks” that serve in fighting or display. These animals take their prey by suction. The narwhal, too, has no grasping dentition: its “tusk” is in fact a single, highly specialised tooth.

Echolocation: a high-precision biosonar

Odontocetes are the only cetaceans capable of echolocation. The mechanism rests on three stages:

  • Emission. The clicks are produced by the phonic lips (or “monkey lips”), located in the nasal passages, just below the blowhole, and not in the melon.
  • Focusing. The melon, a fatty lens in the forehead, shapes the sound beam and directs it forward.
  • Reception. The returning echoes are picked up by a fatty body housed in the hollow lower jaw, which transmits the vibrations to the tympanic bulla (middle ear) and then to the inner ear.

This system, which appeared in the first odontocetes during the Oligocene (about 34 to 23 million years ago), allows navigation and hunting of great precision, including in total darkness or at great depth.

A carnivorous diet and varied hunting strategies

All odontocetes are carnivorous. Their diet includes fish, squid and other cephalopods, crustaceans and, for certain specialised killer whale ecotypes, other marine mammals. Hunting may be solitary or coordinated within a group.

Cognition, sociality and culture

Odontocetes are among the most social and cognitively developed animals:

  • Cultural transmission of hunting techniques and of vocal dialects.
  • Alliances, social play and individual recognition through acoustic “signatures”.
  • Tool use: the best-documented case is sponging by the common bottlenose dolphins (Tursiops) of Shark Bay, Australia, which protect their rostrum with a marine sponge in order to probe the sea floor, a skill passed from mother to daughter.

A few emblematic species

  • Tursiops truncatus: the common bottlenose dolphin, much studied for its communication and its cognition.
  • Orcinus orca: the killer whale, an apex predator with elaborate social strategies and specialised ecotypes.
  • Ziphius cavirostris: Cuvier’s beaked whale holds the mammalian diving records, two distinct ones: down to about 2,992 m and up to nearly 3 h 42 min (222 minutes) of breath-hold (Schorr et al. 2014, PLoS ONE, for the depth).
  • Physeter macrocephalus: the sperm whale, the largest of the odontocetes and holder of the largest brain in the animal kingdom.
  • Monodon monoceros: the narwhal, whose “tusk” is a left canine drawn out into a spiral and richly innervated, with on the order of ten million open dentinal tubules connecting the pulp to the surface (Nweeia et al. 2014), and with sensory functions (salinity, temperature) and a role in sexual selection that are now documented.

Evolutionary origin of the odontocetes

Odontocetes and mysticetes together form the Neoceti (modern cetaceans), descended from four-legged land ancestors. The cetacean lineage separated from that of the hippopotamuses (Whippomorpha) about 53 to 55 million years ago (molecular estimate). It runs through Eocene artiodactyls such as Pakicetus (~50 Ma), semi-aquatic and tied to fresh water, whose closest known relative is the raoellid Indohyus (~48 Ma), then Ambulocetus and Rodhocetus, before the fully marine basilosaurids such as Basilosaurus and Dorudon. The split between odontocetes and mysticetes (within the Neoceti) took place about 34 to 39 million years ago (palaeontological data around 34 Ma); it is also at that period that echolocation appears, in early families such as the Xenorophidae. To go further, see our pages on cetacean evolution, the fossil ancestors, the land ancestor and the interactive phylogeny.

Conservation: among the most threatened species

Several odontocetes are among the most endangered marine mammals, according to the IUCN Red List:

  • Vaquita (Phocoena sinus): Critically Endangered, about ten individuals.
  • Baiji (Lipotes vexillifer): Critically Endangered, possibly extinct.
  • River dolphins (Ganges, Indus, La Plata): Endangered or Vulnerable.

Frequently asked questions

How many odontocete species are there?

The reference list of the Society for Marine Mammalogy (Committee on Taxonomy), regularly updated, recognises about 79 living odontocete species, spread across 10 families, out of a total of about 94 living cetacean species (15 of them mysticetes). The richest family is the Delphinidae (dolphins), with 38 species.

What is the difference between odontocetes and mysticetes?

Odontocetes have teeth, a single blowhole and practise echolocation; they hunt individual prey. Mysticetes have baleen (no teeth), two blowholes and filter large quantities of small prey.

Where are echolocation clicks produced?

The clicks are generated by the phonic lips located in the nasal passages, below the blowhole. The melon does not produce the sound: it acts as an acoustic lens that focuses it forward.

Which odontocete dives the deepest?

Cuvier’s beaked whale (Ziphius cavirostris) holds the mammalian records, with two distinct performances: a dive measured at about 2,992 metres deep and a breath-hold of about 222 minutes (3 h 42 min).

Further reading: identifying a cetacean, recognising a cetacean by its blow, scale comparator and glossary of cetaceans.