''Atocetus'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of pontoporiid

dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...

found in

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

-age marine deposits in

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

and

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

Description

The type species, ''Atocetus iquensis'', is known from

Serravallian The Serravallian is, in the geologic timescale, an List of time periods, age or a stage (stratigraphy), stage in the middle Miocene epoch (geology), Epoch/series (stratigraphy), Series, which spans the time between 13.82 annum, Ma and 11.63 Ma (m ...

-age strata of the

Pisco Formation The Pisco Formation is a geologic formation located in Peru, on the southern coastal desert of Ica, Peru, Ica and Arequipa. The approximately thick formation was deposited in the Pisco Basin, spanning an age from the Miocene, Late Miocene up to t ...

of Peru,De Muizon, 1988, p.131 while ''A. nasalis'' is known from

Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Tort ...

-age marine deposits of the

Modelo Formation The Modelo Formation is a Miocene Formation (geology), geologic formation in the Simi Hills and western Santa Susana Mountains of southern California, including under parts of Los Angeles. It preserves fossils dating back to the Late Miocene of ...

in California. Barnes (1985) originally described the latter as a species of '' Pithanodelphis'', but it was eventually transferred to ''Atocetus'' by Muizon (1988). The Miocene delphinidan ''"Champsodelphis" fuchsii'' from marine deposits in

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

was initially tentatively referred to ''Atocetus'' based on the discovery of partial skeletons from the Carpathian region with earbones similar to those of ''Atocetus'' but was eventually reassigned to ''

Kentriodon ''Kentriodon'' is an extinct genus of toothed whale related to modern-day dolphins. Fossils have been found in North America, Europe and Japan. Several species have been described. Description ''Kentriodon'' was the most diverse of all the ...

'' following the discovery of additional earbones from Austria and

Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...

Phylogeny

Although ''Atocetus'' and other pithanodelphinines are usually assigned to

Kentriodontidae Kentriodontidae is an extinct family of odontocete whales related to modern dolphins. The Kentriodontidae lived from the Oligocene to the Pliocene before going extinct Extinction is the termination of an organism by the death of its End ...

, the cladistic analysis of Lambert et al. (2017) showed that ''Atocetus'' and ''Pithanodelphis'' form a clade with '' Tagicetus'' and ''

Lophocetus ''Lophocetus'' ("crested whale") is an extinct genus of dolphin belonging to the clade Delphinida that is known from late Miocene (Tortonian) marine deposits in California and Maryland. Although usually placed in Kentriodontidae, recent studies h ...

'' that is not only phylogenetically more derived than other kentriodontids but is also phylogenetically intermediate between the

baiji The baiji (''Lipotes vexillifer'') is a probably extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolphin species driven to extinction due to the impact of humans. This dolphin is ...

and members of

Inioidea River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant rive ...

and

Phocoenidae Porpoises () are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas than to the true dolphins. There are eight extant specie ...

. However, a subsequent cladistic analysis by Post et al. (2017) recovers ''Atocetus'' as a member of Pontoporiidae, which includes the franciscana.Post K, Louwye S, Lambert O. (2017) Scaldiporia vandokkumi, a new pontoporiid (Mammalia, Cetacea, Odontoceti) from the Late Miocene to earliest Pliocene of the Westerschelde estuary (The Netherlands) PeerJ 5:e3991 https://doi.org/10.7717/peerj.3991

References

Bibliography

* Kentriodontidae Prehistoric cetacean genera Serravallian life Tortonian life Miocene mammals of North America Neogene California Paleontology in California Fossils of the United States Miocene mammals of South America Laventan Neogene Peru Fossils of Peru Pisco Formation Fossil taxa described in 1988 {{paleo-whale-stub