Monotypic prehistoric cetacean genera

Ambulocetus (from Latin ambulō, meaning "to walk", and cetus, meaning "whale", and thus, "walking whale") is a genus of early semiaquatic cetacean from the Kuldana Formation in Pakistan, roughly 48 or 47 million years ago during the Early Eocene (Lutetian). It contains one species, Ambulocetus natans (Latin natans "swimming"), known solely from one near-complete skeleton. Ambulocetus is among the best-studied of Eocene cetaceans, and serves as an instrumental find in the study of cetacean evolution and their transition from land to sea, as it was the first cetacean discovered to preserve a sui

Livyatan is an extinct genus of macroraptorial sperm whale containing one known species: L. melvillei. The genus name was inspired by the biblical sea monster Leviathan, and the species name by Herman Melville, the author of the famous novel Moby-Dick about a white bull sperm whale. Herman Melville often referred to whales as "Leviathans" in his book. It is mainly known from the Pisco Formation of Peru during the Tortonian stage of the Miocene epoch, about 9.9–8.9 million years ago (mya); however, finds of isolated teeth from other locations such as Chile, Argentina, the United States (Califor

Protocetus atavus ("first whale") is an extinct species of primitive cetacean from Egypt. It lived during the middle Eocene period 45 million years ago. The first discovered protocetid, Protocetus atavus was described by based on a cranium and a number of associated vertebrae and ribs found in middle Lutetian Tethyan marine limestone from the Mokattam Formation at Gebel Mokattam near Cairo, Egypt.

Ichthyolestes (meaning "fish robber" from Ancient Greek ἰχθύς (ikhthús), meaning "fish", and λῃστής (lēistḗs), meaning "robber") is an extinct genus of pakicetid cetacean endemic to the northern Indian subcontinent during the Lutetian age of the Eocene. It is monotypic, with I. pinfoldi as the only species.

Maiacetus ("mother whale") is a genus of early cetacean from the Eocene-aged Habib Rahi Formation of Pakistan.

Perucetus is an extinct genus of an early whale from Peru that lived during the Bartonian age of the middle Eocene. Perucetus is the largest Eocene whale, with length estimates varying from to . It was initially claimed to have rivaled or exceeded the modern blue whale in weight, partly due to the incredibly thick and dense bones this animal possessed, coupled with its already great size, but subsequent studies argued that it was significantly lighter. The ecology of Perucetus also remains largely mysterious. Based on the fossils, it was likely a slow-moving inhabitant of shallow waters. Its d

Zygorhiza ("Yoke-Root") is an extinct genus of basilosaurid early whale known from the Late Eocene (Priabonian, 38–34 Ma) of Louisiana, Alabama, and Mississippi, United States, and the Bartonian (43–37 Ma on the New Zealand geologic time scale) to the late Eocene of New Zealand (). Specimens reported from Europe are considered Dorudontinae incertae sedis.

Kutchicetus is an extinct genus of early whale of the family Remingtonocetidae that lived during Early-Middle Eocene (Lutetian and Ypresian) in what is now the coastal border of Pakistan and India (, paleocoordinates ). It is closely related to Andrewsiphius with which it was synonymized by . proposed a new clade, Andrewsiphiinae, for the two species. Later authors, however, still accept both as separate genera.

Himalayacetus is an extinct genus of carnivorous aquatic mammal of the family Ambulocetidae. The holotype was found in Himachal Pradesh, India, (: paleocoordinates ) in what was the remnants of the ancient Tethys Ocean during the Early Eocene. This makes Himalayacetus the oldest archaeocete known, extending the fossil record of whales some 3.5 million years.

Janjucetus is an extinct genus of baleen whale that lived during the Late Oligocene (Chattian) in south-east Australia, around 25 million years ago. Remains of the genus have been found in the Jan Juc Marl in the Jan Juc Formation near the township of the same name, and have been assigned to two species: the type species J. hunderi and J. dullardi. This locality has yielded remains of more extinct cetaceans, including Prosqualodon, Waipatia, and the related Mammalodon.

Brygmophyseter, known as the biting sperm whale, is an extinct genus of toothed whale in the sperm whale family with one species, B. shigensis. When it was first described in 1994, the species was placed in the genus Scaldicetus based on tooth morphology, but this was later revised in 2006. A month later since the naming of Brygmophyseter, another study classified this species into the genus Naganocetus, which is considered to be a junior synonym. The only known specimen, a nearly complete skeleton, was dated to be around 16–15 million years old (middle Miocene). The Brygmophyseter holotype is

Georgiacetus is an extinct genus of ancient whale known from the Eocene period of the United States. Fossils are known from Georgia, Alabama, and Mississippi and protocetid fossils from the right time frame, but not yet confirmed as Georgiacetus, have been found in Texas () and South Carolina ().

Zygophyseter is an extinct genus of sperm whale that lived during the Tortonian age of the Late Miocene 11.2 to 7.6 million years ago. The genus contains a single species, Zygophyseter varolai, known from a single specimen from the Pietra Leccese Formation in Italy. It was a member of a stem group of fossil macroraptorial sperm whales (often shortened to "raptorial") also including Brygmophyseter, Acrophyseter, and Livyatan. It probably grew to be around in length and shared some characteristics with other raptorials, such as large teeth with tooth enamel that were functional in both the upper

Phiomicetus is a genus of protocetid whale that lived between 43 and 42 million years ago during the Lutetian (middle Eocene) period in what is now Egypt. It had powerful jaws and large teeth that would have allowed it to hunt and tear large prey.

Saghacetus is an extinct genus of basilosaurid early whale, fossils of which have been found in the Upper Eocene (middle Priabonian, ) Qasr el Sagha Formation, Egypt (, paleocoordinates ).

Gandakasia is an extinct genus of ambulocetid from Pakistan, that lived in the Eocene epoch. It probably caught its prey near rivers or streams. Just like Himalayacetus, Gandakasia is only known from a single jaw fragment, making comparisons to other ambulocetids difficult due to the lack of material. Gandakasia probably inhabited a freshwater niche similar to the pakicetids.

Basiloterus is an extinct genus of late-Eocene archaeocete whale from the Drazinda Formation in southwestern Punjab, Pakistan and possibly also the Barton Group (originally Barton Beds) of England. Known from two isolated lumbar vertebrae, the elongated nature of these elements has been taken as possible evidence that Basiloterus was a close relative of the better-known Basilosaurus. This was also the reasoning behind its name, which roughly translates to "another king". However, publications since then not only lead to some major changes of the internal relationships within Basilosauridae but

Semirostrum ceruttii is an extinct porpoise that lived between 5 and 1.5 million years ago (Ma), during the Pliocene epoch. The species is highly distinctive due to the extremely long symphysis on the lower jaw, reaching lengths of , while that of a modern porpoise is long. The main hypothesis regarding its use is that it probed along the sediment in the murky estuaries and shores of what is now California in search of food, which would easily be scooped up the symphysis and into the jaws. It is the only known species in the genus Semirostrum. The etymology of the name means "half beak",

Mystacodon is a genus of toothed baleen whale from the Late Eocene Yumaque Member of Paracas Formation (previously called as Yumaque Formation) of the Pisco Basin in southwestern Peru. It is the oldest known baleen whale, and was probably a suction feeder of small prey on the seafloor.

Eobalaenoptera is an extinct genus of baleen whale belonging to Balaenopteroidea.

Nalacetus is an extinct pakicetid early whale, fossils of which have been found in Lutetian red beds in Punjab, Pakistan (, paleocoordinates ). Nalacetus lived in a fresh water environment, was amphibious, and carnivorous. It was considered monophyletic by . It was said to be wolf-sized and one of the earliest forms of the order Cetacea.

Attockicetus is an extinct genus of remingtonocetid early whale known from the Middle Eocene (Lutetian) Kuldana Formation in the Kala Chitta Hills, in the Attock District of Punjab, Pakistan.

Andrewsiphius is an extinct remingtonocetid early whale known from the Eocene (Lutetian, ) of Gujarat and Kutch, India and Balochistan, Pakistan.

Bohaskaia is an extinct genus of beluga-like odontocete cetacean known from the Early Pliocene of Virginia and North Carolina, United States. It was first named by Jorge Vélez-Juarbe and Nicholas D. Pyenson in 2012 and the type species is Bohaskaia monodontoides.

Indocetus is a protocetid early whale known from the late early Eocene (Lutetian, ) Harudi Formation (, paleocoordinates ) in Kutch, India.

Dalanistes is an extinct genus of remingtonocetid early whale known from the late-early Eocene (Lutetian, ) of Kutch, India and Punjab and Balochistan, Pakistan. Dalanistes is closely related to Remingtonocetus (the type genus of Remingtonocetidae, a slightly more derived family of early whales), but also shares several features with Ambulocetus (the type of Ambulocetidae, earlier more primitive whales), and, with its combination of terrestrial and amphibious adaptations, Dalanistes apparently is an intermediate form between these two groups. Isotopic evidence suggest that Dalanistes had a mar

Supayacetus is an extinct genus of basilosaurid cetacean from the Middle Eocene (Bartonian stage) Paracas Formation of Peru. It has been noted for its relatively small size and basal morphology, with the sternum bearing close resemblance to those of protocetids. Due to this, it has been traditionally placed as one of the basalmost basilosaurids, except for a 2023 study that places it within the family Pachycetinae close to Neoceti. Supayacetus is monotypic, meaning the genus includes only a single species: S. muizoni.

Stromerius is an extinct genus of basilosaurid early whale known from the Late Eocene (Priabonian, ) of Fayum, Egypt (, paleocoordinates ).

Masracetus (from Arabic Masr, "Egypt", and Greek ketos, "whale") is an extinct genus of basilosaurid ancient whale known from the Late Eocene (Priabonian, ) of Egypt.

Makaracetus is an extinct protocetid whale, the remains of which were found in 2004 in Lutetian layers of the Domanda Formation in the Sulaiman Range of Balochistan, Pakistan (, paleocoordinates ).

Artiocetus is an extinct genus of early whales belonging to the family Protocetidae. It was a close relative to Rodhocetus and its tarsals indicate it resembled an artiodactyl.

Aegyptocetus is an extinct genus of protocetid archaeocete whale known from Egypt.

Tutcetus is an extinct genus of diminutive basilosaurid cetacean from the Bartonian of Egypt. Tutcetus, named after the child pharaoh Tutankhamun, is both one of the oldest known basilosaurids from Africa and the smallest member of the family. It is suggested that the type specimen, a subadult close to maturity, only measured approximately long. The genus is monotypic, only including the species T. rayanensis.

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.

Ancalecetus (from Greek ankale, "bent arm", and ketos, "whale") is an extinct genus of early whale known from the Late Eocene (Priabonian, ) Birket Qarun Formation (, paleocoordinates ) in Wadi Al-Hitan, Egypt. The species is named after anthropologist and primate researcher Elwyn L. Simons who discovered the type specimen in 1985.

Arktocara is an extinct genus of river dolphin from the Oligocene epoch of Alaska, containing one species, A. yakataga. Having been discovered in 25-million-year-old strata near the 60th parallel north, it is perhaps the oldest-known crown toothed whale and the northmost river dolphin discovered. It was a member of the now-extinct family Allodelphinidae, along with the genera Allodelphis, Goedertius, Ninjadelphis, and Zarhinocetus. It measured approximately , comparable to its closest living relative, the South Asian river dolphin, which measures . However, the animal probably had an elongated

Ocucajea is an extinct genus of basilosaurid cetacean from Middle Eocene (Bartonian stage) deposits of southern Peru. Ocucajea is known from the holotype MUSM 1442, a partial skeleton. It was collected in the Archaeocete Valley site, from the Paracas Formation of the Pisco Basin about .

Llanocetus ( "Llano's whale" ) is a genus of extinct toothed baleen whales from the Late Eocene of Antarctica and New Zealand. The type species, Llanocetus denticrenatus, reached gigantic proportions, with the juvenile specimen reaching an estimated in length; a second, unnamed species, known only from three isolated premolar teeth, reached an estimated total body length of up to . Like other contemporary baleen whales of the Eocene, Llanocetus completely lacked baleen in its jaws. It was probably a suction feeder like the modern beaked and pygmy right whales.

Gaviacetus (from Latin Gavia, "loon" and cetus, "whale") is an extinct archaeocete whale that lived approximately . Gaviacetus was named for its characteristic narrow rostrum and the fast pursuit predation suggested by its unfused sacral vertebrae.

Rudicetus is an extinct genus of cetacean. thumb|left|Skull

Meherrinia is an extinct genus of inioid river dolphin from the Meherrin River, North Carolina, in the United States. First described in 2012, the dolphin is, in most respects, intermediate in form between the living Amazon river dolphin and the La Plata dolphin, although it is probably more closely related to the former. However, the fossil was discovered in what are believed to be marine deposits, dating from the late Miocene, whereas the Amazon river dolphin is an exclusively freshwater species. Meherrinia therefore was, as of 2012, the only known marine genus of the family Iniidae, althoug

Piscobalaena is an extinct genus of cetaceans, which lived from the Middle to Late Miocene epochs (about 11.6 to 5.3 million years ago) in Peru and Florida. Its fossils have been found in the Pisco Formation of Peru and the Bone Valley Formation of Florida. At least some individuals of this diminutive whale were preyed on by the shark O. megalodon.

Globicetus is an extinct genus of ziphiidae cetaceans, with one species, G. hiberus, from the Miocene of Portugal and Spain. The holotype is a skull in the Museu da Lourinhã, in Portugal. G. hiberus is notable for having a large, spherical mass of bone on its rostrum.

Pappocetus (meaning "grandfather whale") is an extinct protocetid cetacean known from the Eocene of southern Nigeria's Ameki Formation and Togo. More recently, fossil teeth and femurs have also been discovered in the Aridal Formation of the Sahara Desert in southwestern Morocco.

Simocetus (from simus, "pug-nosed", and cetus, "whale") is an extinct genus of toothed whale that lived during the Oligocene period, approximately , making it the oldest named toothed whale, although older unnamed toothed whales exist.

Balaenotus is an extinct genus of cetaceans from the Pliocene of Belgium.

Horopeta is a genus of baleen whale from the Late Oligocene (Chattian) Kokoamu Greensand of New Zealand.

Parabalaenoptera is an extinct genus of baleen whale found in Late Miocene sediments in Marin County, California. The type species is P. baulinensis. It was estimated to be about the size of the modern gray whale, about long. Zeigler placed P. baulinensis in the subfamily Parabalaenopterinae in 1997, a clade which includes an extinct species of rorqual whales, also part of the Balaenopteridae family.

Brandtocetus is a genus of cetotheriid mysticete in the subfamily Cetotheriinae. The type and only species is Brandtocetus chongulek from the late Miocene (Tortonian) of the Kerch Peninsula in Crimea.

Cophocetus is an extinct genus of baleen whale known from Miocene-aged marine strata in Oregon, North America.

thumb|left|E. giulii skull

Takracetus was a primitive cetacean that lived approximately in Pakistan. The type specimen (GSP-UM 3041) is a partial skull though the literature mentions a second more complete specimen.

Aegicetus is an extinct genus of protocetid whale based on a partial skull with much of an associated postcranial skeleton discovered in Egypt. It lived around 35 million years ago (during the Late Eocene), making it the youngest known protocetid to date. Aegicetus was discovered in 2007 at Wadi El Hitan (Gehannam Formation) as a relatively complete skeleton and a partial second specimen. They were assigned to a new genus and species in 2019 by Philip D. Gingerich et al.

Yamatocetus canaliculatus is an extinct species of eomysticetid baleen whale from the Late Oligocene of Japan.

Qaisracetus is an extinct protocetid early whale known from the Eocene (Lutetian, ) of Baluchistan, Pakistan (, paleocoordinates ).

Agorophius is an extinct genus of toothed whale that lived during the Oligocene period, approximately , in the waters off what is now South Carolina.

Morenocetus is an extinct genus of primitive balaenid from the Early Miocene (Burdigalian and Colhuehuapian in the SALMA classification) Gaiman Formation of Patagonia, Argentina.

Willungacetus is an extinct genus of primitive baleen whale of the family Aetiocetidae known from the Oligocene of Australia (at Port Willunga, , paleocoordinates ). It is the oldest-known whale from Australia, and the only aetiocetid whale currently known from the Southern Hemisphere.

Togocetus ("Togo whale") is a genus of extinct cetacean from the Lutetian (lower Eocene) of Togo, known from a fossilized skeleton discovered a few kilometers north-east of Lomé.