| Chilcacetus | |
|---|---|
 | |
| Skull | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Genus: | † Chilcacetus Lambert et al. 2015 |
| Species: | †C. cavirhinus |
| Binomial name | |
| †Chilcacetus cavirhinus Lambert et al. 2015 | |
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. [1]
Chilcacetus is recovered along it with the putative eurhinodelphinids Argyrocetus and Macrodelphinus in a clade basal to Eoplatanista and Eurhinodelphinidae. The authors stressed that updated osteological descriptions of Argyrocetus and Macrodelphinus are necessary to provide more cladistic analysis support for this grouping. [2]
The teeth of Chilcacetus are homodont in nature, and the rostrum is long. The presence of a cavity between nasals and mesethmoid on the posterior wall of the bony nares that distinguishes this taxon from other archaic odontocetes, hence the species name cavirhinus. The dorsal surface of the nasal rising anterodorsally, extended edentulous anterior premaxillary portion of the rostrum, and a cranium distinctly shorter than wide unite Chilcacetus with Argyrocetus and Macrodelphinus to the exclusion of all other homodont odontocetes, including eurhinodelphinids. [2]
Squalodon is an extinct genus of whales of the Oligocene and Miocene epochs, belonging to the family Squalodontidae. Named by Jean-Pierre Sylvestre de Grateloup in 1840, it was originally believed to be an iguanodontid dinosaur but has since been reclassified. The name Squalodon comes from Squalus, a genus of shark. As a result, its name means "shark tooth". Its closest modern relative is the South Asian river dolphin.
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.
Diaphorocetus is an extinct genus of odontocete cetacean belonging to Physeteroidea. Its remains were found in the Monte León Formation of Argentina, dating to the Early Miocene.
Huaridelphis is an extinct genus of river dolphins from the Early Miocene. The type species is H. raimondii, found in the Chilcatay Formation of the Pisco Basin.
Otekaikea is an extinct genus of toothed whale closely related to Waipatia. It is known from the late Oligocene (Chattian) of New Zealand.
Atocetus is an extinct genus of pontoporiid dolphin found in Miocene-age marine deposits in Peru and California.
Allodelphinidae is a family of primitive platanistoid river dolphins found in marine deposits in the eastern North Pacific region, Alaska, and Japan.
Notocetus is an extinct genus of river dolphin belonging to Squalodelphinidae. Known specimens have been found in Early Miocene marine deposits from Argentina, Italy and Peru.
Squaloziphius is an extinct genus of odontocete cetacean from the Early Miocene (Aquitanian) aged marine deposits in Washington state.
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.
Tiucetus is an extinct genus of cetotheriid baleen whale known from the Late Miocene Pisco Formation of Peru.
Phoberodon is a genus of archaic odontocete cetacean from the Early Miocene (Burdigalian) of Patagonia, Argentina.
Morenocetus is an extinct genus of primitive balaenid from the Early Miocene Gaiman Formation of Patagonia, Argentina.
Brachydelphis is a genus of pontoporiid known from the Late Miocene Pisco Formation of Peru and the Bahía Inglesa Formation of Chile.
Inticetus is an extinct genus of Early Miocene odontocete from the Chilcatay Formation, Pisco Basin, Peru.
Macrosqualodelphis is an extinct genus of river dolphins from the Early Miocene (Burdigalian) Chilcatay Formation of the Pisco Basin, Peru. The type species is M. ukupachai.
Romaleodelphis is a genus of extinct archaic toothed whale from the Early Miocene Ebelsberg Formation of Austria. It had long and slender jaws and homodont teeth and roamed the marine waters of the Central Paratethys that once covered much of Europe. Phylogenetic analysis has shown that Romaleodelphis is most closely related to other odotontocetes previously grouped together as the "Chilcacetus clade, now a paraphyletic grade basal to true dolphins and beaked whales. The inner ear of Romaleodelphis shows that it was capable of hearing hearing narrow-band high frequency sounds, an ability it convergently evolved with several modern types of whales. It is possible that this was a useful tool in evading other predatory whales, though some recent research suggests that it may have also been an early step in the development of the cetacean biosonar.
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