| Eobalaenoptera Temporal range: middle Miocene | |
|---|---|
 | |
| Skeleton, Caroline County, Virginia | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Genus: | † Eobalaenoptera Dooley, Fraser & Luo, 2004 |
| Species: | †E. harrisoni |
| Binomial name | |
| †Eobalaenoptera harrisoni Dooley, Fraser & Luo, 2004 | |
Eobalaenoptera is an extinct genus of baleen whale belonging to Balaenopteroidea.
Eobalaenoptera was first described in June 2004 by researchers at the Virginia Museum of Natural History from a partial skeleton found in 1990 in Caroline County, Virginia, the site of a prehistoric ocean, in the middle Miocene Calvert Formation. The 11 m (36 ft) skeleton proved to have similar morphological characteristics to a clade of whales consisting of two modern taxonomic families—Balaenopteridae (the rorquals) and Eschrichtiidae (a family with one surviving species, the gray whale).
The age of the Calvert Formation (14 million years) makes Eobalaenoptera the oldest-known member of Balaenopteroidea by three to five million years. It also considerably narrowed the gap between the earliest-known fossil record and estimated time of divergence of this clade from other baleen whales. Molecular clocks have put this divergence for balaenopteroids from other crown mysticetes by 15–20 million years. [1] [2]
In their review of extant and fossil rorquals, Demere et al. (2005) questioned the balaenopteroid placement of Eobalaenoptera, noting that the holotype lack substantial cranial material that could reinforce its original classification, preferring to treat the genus as Chaeomysticeti incertae sedis. [3]
The genus name Eobalaenoptera reflects the similarities between this skeleton and species in the genus Balaenoptera such as the minke whale; eo- is a prefix meaning dawn. The species is named after Carter Harrison, a volunteer worker at the museum.
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.
Rorquals are the largest group of baleen whales, which comprise the family Balaenopteridae, containing ten extant species in three genera. They include the largest animal that has ever lived, the blue whale, which can reach 180 tonnes, and the fin whale, which reaches 120 tonnes ; even the smallest of the group, the northern minke whale, reaches 9 tonnes.
Baleen whales, also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea which use keratinaceous baleen plates in their mouths to sieve planktonic creatures from the water. Mysticeti comprises the families Balaenidae, Balaenopteridae (rorquals), Eschrichtiidae and Cetotheriidae. There are currently 16 species of baleen whales. While cetaceans were historically thought to have descended from mesonychids, molecular evidence instead supports them as a clade of even-toed ungulates (Artiodactyla). Baleen whales split from toothed whales (Odontoceti) around 34 million years ago.
Balaenidae is a family of whales of the parvorder Mysticeti that contains mostly fossil taxa and two living genera: the right whale, and the closely related bowhead whale.
Neobalaenidae is a family of baleen whales including the extant pygmy right whale. Although traditionally considered related to balaenids, a recent phylogenetic study by Fordyce and Marx (2013) recovered the living pygmy right whale as a member of Cetotheriidae, making it the only extant cetotheriid, but not all authors agree with this argument.
The pygmy right whale is a species of baleen whale. It may be a member of the cetotheres, a family of baleen whales which until 2012 were thought to be extinct; C. marginata has otherwise been considered the monotypic taxon sole member of the family Neobalaenidae and is the only member of the genus Caperea. First described by John Edward Gray in 1846, it is the smallest of the baleen whales, ranging between 6 and 6.5 metres in length and 3,000 and 3,500 kilograms in mass. Despite its name, the pygmy right whale may have more in common with the gray whale and rorquals than the bowhead and right whales.
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.
The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates 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 5 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.
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.
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.
Balaenula is an extinct genus of cetacean.
Herpetocetus is a genus of cetotheriid mysticete in the subfamily Herpetocetinae.
Protororqualus is a genus of extinct rorqual from the late Pliocene of Mount Pulgnasco, Italy.
Plesiocetus is a genus of extinct balaenopterids found worldwide. It has had a chequered taxonomic history, having served as a wastebasket genus for a handful of mysticete species.
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.
Peripolocetus is a genus of balaenid baleen whale from the middle Miocene of Kern County, California.
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.
Balaenoptera siberi is an extinct species of baleen whale from the Late Miocene, described by Pilleri and Pilleri in 1989, based on fossils found in the Pisco Formation of the Pisco Basin in southwestern Peru.
Norrisanima miocaena is an extinct species of Balaenopteroidea from the late Miocene of California. It was originally considered a species of Megaptera, but is now considered a stem-balaenopteroid.
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