| Plesiocetus | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Balaenopteridae |
| Genus: | † Plesiocetus Van Beneden 1859 |
| Species | |
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| Synonyms | |
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Plesiocetus is a genus of extinct rorquals found worldwide. It has had a chequered taxonomic history, having served as a wastebasket genus for a handful of mysticete species.
The genus Plesiocetus was originally coined for three mysticete species from Neogene marine deposits in the vicinity of Antwerp, Belgium: P. garopii, P. hupschii, and P. burtinii. [1]
The three originally included species of Plesiocetus went about their separate ways. P. garopii was designated the type species of the genus, while the other two were referred to Cetotherium . [2] (P. hupschii and P. burtinii were later assigned to Plesiocetopsis , which was originally erected as a subgenus of Cetotherium [3] ) Later, van Beneden noted the similarities of Plesiocetus with the fin whale, so he renamed Plesiocetus garopii into Balaenoptera musculoides, which is invalid under current ICZN rules. At the same time, he also erected the new species P. brialmontii on the basis of fragmentary remains, while referring Cetotherium dubius to Plesiocetus.
The taxonomy of Plesiocetus by now was confused. Plesiocetus garopii was referred to Balaenoptera (making Plesiocetus a synonym of Balaenoptera), while P. hupschii and P. burtinii were assigned to Cetotherium. [4] [5] To avoid nomenclatorial complications, Plesiocetus hupschii was designated the type species of Plesiocetopsis, removing any synonymy between Plesiocetus and Plesiocetopsis. [6] Recent studies, however, indicate that Plesiocetus shares no characters with Balaenoptera to the exclusion of other balaenopterids. [7] [8] For its part, P. burtinii was referred to Aglaocetus , while P. brialmontii was declared a nomen dubium. [8] These revisions left P. garopii the type and only species of Plesiocetus.
In 2021, a thorough review of Plesiocetus by Bisconti and Bosselaers led its authors to the conclusion that "Plesiocetus is a nomen dubium and must be abandoned by mysticete taxonomists". [9]
Fossils of Plesiocetus have been found in: [10]
Eschrichtiidae or the gray whales is a family of baleen whale with a single extant species, the gray whale, as well as three described fossil genera: Archaeschrichtius and Eschrichtioides from the Miocene and Pliocene of Italy respectively, and Gricetoides from the Pliocene of North Carolina. More recent phylogenetic studies have found this family to be invalid, with its members nesting inside the Balaenopteridae. The names of the extant genus and the family honours Danish zoologist Daniel Eschricht.
Neobalaenidae is a family of baleen whales including the extant pygmy right whale. Although traditionally considered related to balaenids, recent studies by Fordyce and Marx (2013) and Ludovic Dutoit and colleagues (2023) have recovered the living pygmy right whale as a member of Cetotheriidae, making it the only extant cetotheriid. Not all authors agree with this placement.
Balaenoptera is a genus of rorquals containing eight extant species. Balaenoptera comprises all but two of the extant species in its family ; the genus is currently polyphyletic, with the two aforementioned species being phylogenetically nested within it.
Cetotherium is an extinct genus of baleen whales from the family Cetotheriidae.
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.
Ontocetus is an extinct genus of walrus, an aquatic carnivoran of the family Odobenidae, endemic to coastal regions of the southern North Sea and the southeastern coastal regions of the U.S. during the Miocene-Pleistocene. It lived from 13.6 mya—300,000 years ago, existing for approximately 13.3 million years.
Parabalaenoptera is a genus of prehistoric baleen whale found in Marin County, California. The type species is P. baulinensis. It was estimated to be about the size of the modern gray whale, about 16 metres (52 ft) long. It lived during the late Miocene.
Cetotheriidae is a family of baleen whales. The family is known to have existed from the Late Oligocene to the Early Pleistocene before going extinct. Although some phylogenetic studies conducted by Fordyce & Marx 2013 recovered the living pygmy right whale as a member of Cetotheriidae, making the pygmy right whale the only living cetotheriid, other authors either dispute this placement or recover Neobalaenidae as a sister group to Cetotheriidae.
Parietobalaena is an extinct genus of baleen whale, belonging to the family Pelocetidae. Fossils are found in Miocene-aged marine strata in North America, Europe, Australia, and Japan, including the Temblor and Itahashi formations. Based on previous estimates of juvenile specimens, Tsai (2017) suggested a body size of 12-15 m for P. yamaokai, akin to that of the gray whale.
Scaldicetus is an extinct genus of highly predatory macroraptorial sperm whale. Although widely used for a number of extinct physeterids with primitive dental morphology consisting of enameled teeth, Scaldicetus as generally recognized appears to be a wastebasket taxon filled with more-or-less unrelated primitive sperm whales.
Herpetocetus is a genus of cetotheriid mysticete in the subfamily Herpetocetinae. Considerably smaller than modern baleen whales, Herpetocetus measured only 3-4 meters in length. Additionally, due to the structure of its jaw, it was unable to open it as wide as modern baleen whales, making it incapable of lunge feeding.
Protororqualus is a genus of extinct rorqual from the late Pliocene of Mount Pulgnasco, Italy.
Eschrichtioides is an extinct genus of baleen whale known from the early Pliocene of northern Italy. Its type species, E. gastaldii, had a complex taxonomic history, starting as a cetothere, then as an extinct member of Balaenoptera, before being finally recognized as a relative of the gray whale.
Cetotheriopsis is a genus of extinct cetaceans of the family Cetotheriopsidae.
Eomysticetus is an extinct genus of baleen whale from the late Oligocene (Chattian) Chandler Bridge Formation of South Carolina.
Aglaocetus is a genus of extinct baleen whales known from the Miocene of Patagonia, the US Eastern Seaboard, Japan and the Low Countries. It was once considered a member of Cetotheriidae along with many other putative cetotheres, but was recently recognized as representing a distinct family from true Cetotheriidae.
Nannocetus is an extinct baleen whale belonging to the family Cetotheriidae.
Isocetus is an extinct genus of baleen whale belonging to the clade Thalassotherii. Remains have been found in middle Miocene marine deposits in Belgium.
Eudelphis is an extinct genus of sperm whale belonging to Physeteroidea that lived in the ancient North Sea basin about 16-11 million years ago, during the middle Miocene (Langhian).
