| Xenorophus Temporal range: Late Oligocene, | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | † Xenorophidae |
| Genus: | † Xenorophus Kellogg, 1923 |
| Species | |
X. sloaniiKellogg, 1923 Contents | |
Xenorophus is a genus of primitive odontocete from late Oligocene (Chattian) marine deposits in South Carolina. It belongs to the Xenorophidae.
Xenorophus was originally described on the basis of a skull from the Chandler Bridge Formation of South Carolina in the collections of the USNM. [1] Later authors, but also Remington Kellogg who described the genus, classified it in the family Agorophiidae, which eventually became a repository for primitive odontocetes. Whitmore and Sanders (1977) and Fordyce (1981), however, preferred to treat Xenorophus as Odontoceti incertae sedis. [2] [3] [4] [5] A cladistic analysis by Mark Uhen published in 2008 recognized Xenorophus as belonging with Archaeodelphis and Albertodelphis in an odontocete clade more primitive than Agorophius or Simocetus , and named it Xenorophidae. [6]
Xenorophus was capable of echolocation like modern dolphins, judging from the cranial features of two other xenorophids, Echovenator and Cotylocara [7] [8] and from the shape of its own skull. [9] It had an estimated body length of 2.6 to 3 metres (8 ft 6 in to 9 ft 10 in). [9]
The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. Cetaceans are fully aquatic marine mammals belonging to the order Artiodactyla and branched off from other artiodactyls around 50 mya. Cetaceans are thought to have evolved during the Eocene, the second epoch of the present-extending Cenozoic Era. Molecular and morphological analyses suggest Cetacea share a relatively recent closest common ancestor with hippopotami and that they are sister groups. Being mammals, they surface to breathe air; they have five finger bones (even-toed) in their fins; they nurse their young; and, despite their fully aquatic life style, they retain many skeletal features from their terrestrial ancestors. Research conducted in the late 1970s in Pakistan revealed several stages in the transition of cetaceans from land to sea.
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.
Archaeoceti, or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene. Representing the earliest cetacean radiation, they include the initial amphibious stages in cetacean evolution, thus are the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti. This initial diversification occurred in the shallow waters that separated India and Asia 53 to 45 mya, resulting in some 30 species adapted to a fully oceanic life. Echolocation and filter-feeding evolved during a second radiation 36 to 35 mya.
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.
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.
Kentriodontidae is an extinct family of odontocete whales related to modern dolphins. The Kentriodontidae lived from the Oligocene to the Pliocene before going extinct.
Remingtonocetidae is a diverse family of early aquatic mammals of the order Cetacea. The family is named after paleocetologist Remington Kellogg.
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.
The Ashley Formation is a geologic formation in South Carolina. It preserves fossils dating back to the Paleogene period.
Otekaikea is an extinct genus of toothed whale closely related to Waipatia. It is known from the late Oligocene (Chattian) of New Zealand.
Microcetus is a genus of extinct odontocete from the late Oligocene (Chattian) of Nordrhein-Westfalen, Germany.
Lophocetus 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 have found it only distantly related to Kentriodon.
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.
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.
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.
Archaeodelphis is an extinct genus of primitive odontocete cetacean from late Oligocene (Chattian) marine deposits in South Carolina, and belonging to the family Xenorophidae.