| Prorastomus Temporal range: | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Sirenia |
| Family: | † Prorastomidae |
| Genus: | † Prorastomus Owen, 1855 |
| Species: | †P. sirenoides |
| Binomial name | |
| †Prorastomus sirenoides Owen, 1855 | |
Prorastomus sirenoides is an extinct species of primitive sirenian that lived during the Eocene Epoch 40 million years ago in Jamaica.
The generic name Prorastomus, a combination of Greek πρῷρα (prōra), prow, and στόμα (stoma), mouth, refers to the lower jaw of the animal "resembling the prow of a wherry".
The genus name Prorastomus comes from Greek prora meaning "prow" and Latin stomus meaning "mouth." In 1892, naturalist Richard Lydekker respelled it as Prorastoma with a feminine ending, however this was unjustified as stomus is masculine in Latin. [1]
Prorastomus is one of two genera of the family Prorastomidae, the other Pezosiren . These two species are the oldest sirenians, dating to the Eocene. [1]
The first specimen was described by paleontologist Sir Richard Owen in 1855, and, being found in Jamaica in the Yellow Limestone Group, pointed to the origin of Sirenia as being in the New World rather than the Old World as was previously thought. However, the modern understanding of Afrotheria as a clade that originally diversified in Africa overturns this idea. The holotype specimen, BMNH 44897, comprises a skull, jaw, and atlas of the neck vertebrae. When Owen first acquired the skull, it was broken in two between the eyes and the braincase. Another specimen was found in 1989 in the same formation, USNM 437769, comprising the frontal bone, a tusk, vertebrae fragments, and ribs. [1]
While modern sirenians are fully aquatic, the 1.5-metre (5 ft)Prorastomus was predominantly terrestrial, judging from the structure of its skull. Judging from its crown-shaped molars and the shape of its snout, it fed on soft plants. [2] The snout is long, narrow, and, at the tip, bulbous. The nasal bones are larger than other sirenians. The nasal ridge is well developed, indicating it had a good sense of smell. The frontal bones are smaller than usual for sirenians, though, as in other sirenians, it had a pronounced brow ridge. [1] Since Pezosiren has a sagittal crest, it is possible the Prorastomus specimen had one too before being eroded away. [3]
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.
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.
Basilosaurus is a genus of large, predatory, prehistoric archaeocete whale from the late Eocene, approximately 41.3 to 33.9 million years ago (mya). First described in 1834, it was the first archaeocete and prehistoric whale known to science. Fossils attributed to the type species B. cetoides were discovered in the United States. They were originally thought to be of a giant reptile, hence the suffix "-saurus", Ancient Greek for "lizard". The animal was later found to be an early marine mammal, which prompted attempts at renaming the creature, which failed as the rules of zoological nomenclature dictate using the original name given. Fossils were later found of the second species, B. isis, in 1904 in Egypt, Western Sahara, Morocco, Jordan, Tunisia, and Pakistan. Fossils have also been unearthed in the southeastern United States and Peru.
Ouranosaurus is a genus of herbivorous basal hadrosauriform dinosaur that lived during the Aptian stage of the Early Cretaceous of modern-day Niger and Cameroon. Ouranosaurus measured about 7–8.3 metres (23–27 ft) long and weighed 2.2 metric tons. Two rather complete fossils were found in the Elrhaz Formation, Gadoufaoua deposits, Agadez, Niger, in 1965 and 1970, with a third indeterminate specimen known from the Koum Formation of Cameroon. The animal was named in 1976 by French paleontologist Philippe Taquet; the type species being Ouranosaurus nigeriensis. The generic name is a combination of ourane, a word with multiple meanings, and sauros, the Greek word for lizard. The specific epithet nigeriensis alludes to Niger, its country of discovery. And so, Ouranosaurus nigeriensis could be interpreted as "brave lizard originating from Niger".
Scelidosaurus is a genus of herbivorous armoured ornithischian dinosaur from the Jurassic of the British Isles.
Altirhinus is a genus of hadrosauroid ornithopod dinosaur from the Early Cretaceous period of Mongolia.
Monolophosaurus is an extinct genus of tetanuran theropod dinosaur from the Middle Jurassic Shishugou Formation in what is now Xinjiang, China. It was named for the single crest on top of its skull. Monolophosaurus was a mid-sized theropod at about 5–5.5 metres (16–18 ft) long and weighed 475 kilograms (1,047 lb).
Majungasaurus is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period, making it one of the last-known non-avian dinosaurs that went extinct during the Cretaceous–Paleogene extinction event. The genus contains a single species, Majungasaurus crenatissimus. This dinosaur is also called Majungatholus, a name which is considered a junior synonym of Majungasaurus.
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.
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.
Eotheroides is an extinct genus of Eocene sirenian. It is an early member of the family Dugongidae, which includes the extant dugong. Fossils have been found from Egypt, India, and Madagascar. Eotheroides was first described by Richard Owen in 1875 under the name Eotherium, which was replaced by the current name in 1899.
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.
Prorastomidae is a family of extinct sirenians from Jamaica, related to the extant manatees and dugong. The family includes the oldest known fossils of Sirenians, represented in two genera:
Sarahsaurus is a genus of basal sauropodomorph dinosaur which lived during the Early Jurassic period in what is now northeastern Arizona, United States.
Arcusaurus is an extinct genus of sauropodomorph dinosaur from the Early Jurassic of South Africa.
Eocetus is an extinct protocetid early whale known from the early late Eocene Giushi Formation in Gebel Mokattam, outside Cairo, Egypt. The specimen was first named by Fraas as Mesocetus schweinfurthi. However, the name Mesocetus was previously used causing a change to the species name to Eocetus schweinfurthi. Since the genus was first described in the early 20th century, several other specimens, mostly isolated vertebrae, have been attributed to Eocetus, but the taxonomic status of these widely distributed specimens remain disputed.
This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.
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.
Sobrarbesiren is a genus of extinct sirenian that lived in the Eocene, about 47 million years ago. The type and only species is S. cardieli, known from a multitude of specimens from the Spanish Pyrenees. Sobrarbesiren was a medium-sized animal, 2.7 m long and still retaining both pairs of limbs. Although initially thought to be amphibious, later studies instead suggest that they would have been fully aquatic and been selective sea grass browsers. Unlike modern dugongs and manatees, they likely lacked a tail fluke, although it would have appeared horizontally flattened.
Sirenian genera | ||
|---|---|---|
| ||
 | ||
 | This article about prehistoric Afrotheria is a stub. You can help Wikipedia by expanding it. |
