 | This article relies largely or entirely on a single source .(October 2023) |
| Stegosiren | |
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| Stegosiren skeleton at Mace Brown Museum of Natural History | |
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| Genus: | Stegosiren |
Stegosiren was an early sea cow from the Middle Oligocene of South Carolina, US. It shows a stage of halitheriine evolution more derived than that of the Old World early Oligocene Eosiren imenti and Halitherium schinzii .
Fossils of Stegosiren are known from the Middle Oligocene of South Carolina, US. [1]
As of March 2021, the addition of Stegosiren macei to the list of potentially sympatric sirenian species lineages known from the West Atlantic-Caribbean Oligocene brings the total number of those to at least seven. [1]
The species is from the Ashley and Chandler Bridge Formations in South Carolina (late Rupelian–late Chattian) and reflect a stage of halitheriine evolution more derived than that of the Old World early Oligocene Eosiren imenti and Halitherium schinzii, but slightly less derived than the West Atlantic late Oligocene Metaxytherium albifontanum. [1] Its early Oligocene contemporaries Caribosiren turneri and Priscosiren atlantica are more similar in stage of evolution, and it may be a sister taxon to these two. Stegosiren is differentiated from all other sirenians by a noticeably broadened head. [1]
Ecomorphology and feeding-niche partitioning are complicated by the sirenian diversity. [1]
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich from his studies of marine beds in Belgium and Germany. The name comes from the Ancient Greek ὀλίγος and καινός, and refers to the sparsity of extant forms of molluscs. The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period.
The Sirenia, commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The extant Sirenia comprise two distinct families: Dugongidae and Trichechidae with a total of four species. The Protosirenidae and Prorastomidae families are extinct. Sirenians are classified in the clade Paenungulata, alongside the elephants and the hyraxes, and evolved in the Eocene 50 million years ago (mya). The Dugongidae diverged from the Trichechidae in the late Eocene or early Oligocene.
A passerine is any bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds, passerines generally have an anisodactyl arrangement of their toes, which facilitates perching.
Dugongidae is a family in the order of Sirenia. The family has one surviving species, the dugong, one recently extinct species, Steller's sea cow, and a number of extinct genera known from fossil records.
The Desmostylia are an extinct order of aquatic mammals native to the North Pacific from the early Oligocene (Rupelian) to the late Miocene (Tortonian). Desmostylians are the only known extinct order of marine mammals.
Caviomorpha is the rodent infraorder or parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now accepted as a genuine part of the rodents. Caviomorphs include the extinct Heptaxodontidae, the extinct Josephoartigasia monesi and extant families of chinchilla rats, hutias, guinea pigs and the capybara, chinchillas and viscachas, tuco-tucos, agoutis, pacas, pacaranas, spiny rats, New World porcupines, coypu and octodonts.
Halitherium is an extinct dugongid sea cow that arose in the late Eocene, then became extinct during the early Oligocene. Its fossils are common in European shales. Inside its flippers were finger bones that did not stick out. Halitherium also had the remnants of back legs, which did not show externally. However, it did have a basic femur, joined to a reduced pelvis. Halitherium also had elongated ribs, presumably to increase lung capacity to provide fine control of buoyancy. A 2014 review presented the opinion that the genus is dubious.
Prorastomus sirenoides is an extinct species of primitive sirenian that lived during the Eocene Epoch 40 million years ago in Jamaica.
Sirenia is the order of placental mammals which comprises modern "sea cows" and their extinct relatives. They are the only extant herbivorous marine mammals and the only group of herbivorous mammals to have become completely aquatic. Sirenians are thought to have a 50-million-year-old fossil record. They attained modest diversity during the Oligocene and Miocene, but have since declined as a result of climatic cooling, oceanographic changes, and human interference. Two genera and four species are extant: Trichechus, which includes the three species of manatee that live along the Atlantic coasts and in rivers and coastlines of the Americas and western Africa, and Dugong, which is found in the Indian and Pacific oceans.
Pezosiren portelli, also known as the "walking manatee", is a basal sirenian from the early Eocene of Jamaica, 50 million years ago. The type specimen is represented by a Jamaican fossil skeleton, described in 2001 by Daryl Domning, a marine mammal paleontologist at Howard University in Washington, DC. It is believed to have had a hippopotamus-like amphibious lifestyle, and is considered a transitional form between land and sea mammals.
Metaxytherium is an extinct genus of dugong that lived from the Oligocene until the end of the Pliocene. Fossil remains have been found in Africa, Europe, North America and South America. Generally marine seagrass specialists, they inhabited the warm and shallow waters of the Paratethys, Mediterranean, Caribbean Sea and Pacific coastline. American species of Metaxytherium are considered to be ancestral to the North Pacific family Hydrodamalinae, which includes the giant Steller's Sea Cow.
Eosiren is an extinct genus of sea cow that lived during the Late Eocene to Early Oligocene (Rupelian). Several fossils have been found in Egypt. It seems like the species E. abeli were contemporaneous with Protosiren and Eotheroides. like them, Eosiren closely resembled modern sirenians. It differs from them by having somewhat larger innominates and possess thigh bones.
The Ashley Formation is a geologic formation in South Carolina. It preserves fossils dating back to the Paleogene period.
The Chandler Bridge Formation is a geologic formation in South Carolina. It preserves fossils dating back to the Chattian of the Paleogene period, corresponding to the Arikareean in the NALMA classification. The formation overlies the Ashley Formation and is overlain by the Edisto Formation.
Miosiren is an extinct genus of manatee from the Early Miocene of southeastern England (Suffolk) and Antwerp, Belgium.
Lentiarenium was an early sea cow from the Late Oligocene (Chattian) Linz-Melk Formation of Austria. Known since the mid 19th century, Lentiarenium was long considered to be a species of Halitherium until a 2016 analysis showed it to be distinct.
Italosiren is an extinct genus of early dugong from the Early Miocene (Aquitanian) Libano Formation in northern Italy.
Priscosiren is an extinct genus of mammal which existed in the west Atlantic and Puerto Rico during the early Oligocene (Chattian).
Kaupitherium is an extinct dugongid sea cow that lived during the Oligocene. Fossils of the genus have been found in the Alzey Formation of Germany. Inside its flippers were finger bones that did not stick out. Kaupitherium also had the residues of back legs, which did not show externally. However, it did have a basic femur, joined to a reduced pelvis. Kaupitherium also had elongated ribs, presumably to increase lung capacity to provide fine control of buoyancy.
Crenatosiren is an extinct genus of dugongid sirenian known from the late Oligocene (Chattian) of Florida, North Carolina, and South Carolina. The type and only known species is Crenatosiren olseni.
Sirenian genera | ||
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