Kogiidae is a family comprising at least two extant species of Cetacea, the pygmy and dwarf sperm whales. As their common names suggest, they somewhat resemble sperm whales, with squared heads and small lower jaws, but are much smaller in size, with much shorter skulls and more notable dorsal fins than sperm whales. Kogiids are also characterized by a "false gill slit" behind their eyes.
Blainville's beaked whale, or the dense-beaked whale, is believed to be the widest ranging mesoplodont whale. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw — the heaviest bone he had ever come across — which resulted in the name densirostris. Off the northeastern Bahamas, the animals are particularly well documented, and a photo identification project started sometime after 2002.
Odobenocetops is an extinct genus of small toothed whale known from Chile and Peru. Its fossils are found in Miocene-aged marine strata of the Bahía Inglesa Formation and Pisco Formation. Two species of Odobenocetops are currently recognized, O. peruvianus and the slightly younger O. leptodon.
Macrodelphinus is an extinct genus of primitive odontocete known from Early Miocene marine deposits in California.
Aetiocetus is a genus of extinct basal mysticete, or baleen whale that lived 33.9 to 23.03 million years ago, in the Oligocene in the North Pacific ocean, around Japan, Mexico, and Oregon, U.S. It was first described by Douglas Emlong in 1966 and currently contains known four species, A. cotylalveus, A. polydentatus, A. tomitai, and A. weltoni. These whales are remarkable for their retention of teeth and presence of nutrient foramina, indicating that they possessed baleen. Thus, Aetiocetus represents the transition from teeth to baleen in Oligocene mysticetes. Baleen is a highly derived character, or synapomorphy, of mysticetes, and is a keratinous structure that grows from the palate, or roof of the mouth, of the whale. The presence of baleen is inferred from the fossil record in the skull of Aetiocetus. Aetiocetus is known from both sides of the Pacific Ocean: it was first documented in Oregon, United States, but it is also known from Japan and Mexico. The genus is currently constrained to the Northern hemisphere and has little value in biostratigraphic studies of the Oligocene due to its limited occurrences across the Pacific.
Australodelphis mirus is an extinct Pliocene dolphin. A. mirus is known from fossils found in the Sørsdal Formation, Mule Peninsula, Vestfold Hills, East Antarctica. The genus has been described as an example of convergent evolution with beaked whales.
Xenorophidae is an extinct family of odontocetes, currently known from the Oligocene of the Southeastern United States. Known genera of xenorophids include Albertocetus, Archaeodelphis, Xenorophus, Cotylocara, Echovenator, and Inermorostrum.
Eomysticetidae is a family of extinct mysticetes belonging to Chaeomysticeti. It is one of two families in the basal chaeomysticete clade Eomysticetoidea.
Allodelphinidae is a family of primitive platanistoid river dolphins found in marine deposits in the eastern North Pacific region, Alaska, and Japan.
Coronodon is a genus of toothed (transitional) baleen whales from the Early Oligocene Ashley and Chandler Bridge formations of South Carolina. The genus contains three species: the type species C. havensteini, and additional species C. newtonorum and C. planifrons.
Agorophius is an extinct genus of toothed whale that lived during the Oligocene period, approximately 32 million years ago, in the waters off what is now South Carolina.
Mirocetus is a genus of archaic odontocete from the late Oligocene (Chattian) of Azerbaijan. Like many other primitive odontocetes, its classification has been fluid since its description.
Xenorophus is a genus of primitive odontocete from late Oligocene (Chattian) marine deposits in South Carolina. It belongs to the Xenorophidae.
Echovenator is a genus of primitive odontocete from late Oligocene (Chattian) marine deposits in South Carolina. It belongs to the Xenorophidae.
Cotylocara is a genus of primitive odontocete from late Oligocene (Chattian) marine deposits of the Chandler Bridge Formation of South Carolina. It belongs to the Xenorophidae.
Albertocetus is an extinct genus of primitive odontocete cetacean from early Oligocene (Rupelian) marine deposits in North Carolina, and belonging to the family Xenorophidae.
Brachydelphis is a genus of pontoporiid known from the Late Miocene Pisco Formation of Peru and the Bahía Inglesa Formation of Chile.
Chilcacetus is an extinct genus of primitive odontocete known from Early Miocene (Aquitanian) of Peru. Fossils were found in and named after the Chilcatay Formation of the Pisco Basin.
Archaeodelphis is an extinct genus of primitive odontocete cetacean from late Oligocene (Chattian) marine deposits in South Carolina, and belonging to the family Xenorophidae.
Inticetus is an extinct genus of Early Miocene odontocete from the Chilcatay Formation, Pisco Basin, Peru.
