Eotheroides Temporal range: Middle - Late Eocene, | |
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Eotheroides sp. in Artis, Amsterdam. | |
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Genus: | Eotheroides Palmer, 1899 |
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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.
Based on endocranial casts, Eotheroiodes had a smaller endocranial volume than other contemporaneous sirenians such as Protosiren . Unlike extant sirenians, Eotheroides possesses a tentorium cerebelli, which appears as a distinct transverse groove on the skull. [1]
The type species, E. aegyptiacum, is known from the Lutetian Mokattam Limestone of Cairo, Egypt. [1] Another species, E. lambondrano, was recently[ when? ] named on the basis of material found from Middle Eocene nearshore marine deposits in the Mahajanga Basin of Madagascar. The species was named after the Malagasy word for dugong, which translates as "water bushpig". It is known from a nearly complete skull and fragments of pachyosteosclerotic (thick) ribs. Based on its age and morphology, E. lambondrano may be ancestral to E. aegyptiacum. [2] Described in 2009, E. lambondrano is the first pre-Pleistocene Cenozoic mammal named from Madagascar, being known from an 80-million-year gap in the island's fossil record. [3]
Several other species have been named, including E. babiae from India, [4] E. majus, E. clavigerum and E. sandersi from Egypt, [5] [6] and E. waghapadarensis, also from India. [7] E. majus was based on a single upper molar, which was never catalogued and is now lost; [6] it has been considered a senior subjective synonym of E. aegyptiacum. [8]
The teeth of Eotheroides were relatively unspecialized compared to those of extant sirenians, which are reduced as an adaptation for feeding on sea grass. The upper molars of E. lambondrano are considerably longer and wider than those of E. aegyptiacum, suggesting that they were less specialized. [1] Eotheroides is likely to have been one of the first fully aquatic sea cows. Eotheroides lambondrano was found in association with the remains of other sea cows, crocodilians, and sea turtles, which suggests that the locality is representative of a coastal or estuarine environment. [3]
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.
Hydrodamalis is a genus of extinct herbivorous sirenian marine mammals. It included the Steller's sea cow, the Cuesta sea cow, and the Takikawa sea cow. The fossil genus Dusisiren is regarded as the sister taxon of Hydrodamalis: together, the two genera form the dugong subfamily Hydrodamalinae. They were the largest member of the order Sirenia, whose only extant members are the dugong and the manatees. They reached up to 9 metres (30 ft) in length, making the Steller's sea cow among the largest mammals other than whales to have existed in the Holocene epoch. Steller's sea cow was first described by Georg Wilhelm Steller,
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, prompting 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.
Dorudon ("spear-tooth") is a genus of extinct basilosaurid ancient whales that lived alongside Basilosaurus 40.4 to 33.9 million years ago in the Eocene. It was a small whale, with D. atrox measuring 5 metres (16 ft) long and weighing 1–2.2 metric tons. Dorudon lived in warm seas around the world and fed on small fish and mollusks. Fossils have been found along the former shorelines of the Tethys Sea in present-day Egypt and Pakistan, as well as in the United States, New Zealand and Western Sahara.
Wādī al-Ḥītān is a paleontological site in the Faiyum Governorate of Egypt, some 150 kilometres (93 mi) south-west of Cairo. It was designated a UNESCO World Heritage Site in July 2005 for its hundreds of fossils of some of the earliest forms of whale, the archaeoceti. The site reveals evidence for the explanation of one of the greatest mysteries of the evolution of whales: the emergence of the whale as an ocean-going mammal from a previous life as a land-based animal.
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.
Protosiren is an extinct early genus of the order Sirenia. Protosiren existed throughout the Lutetian to Priabonian stages of the Middle Eocene. Fossils have been found in the far-flung locations like the United States, Africa (Egypt), Europe and Asia.
Remingtonocetidae is a diverse family of early aquatic mammals of the order Cetacea. The family is named after paleocetologist Remington Kellogg.
The Jebel Qatrani Formation is a geologic formation located in the Faiyum Governorate of central Egypt. It is exposed between the Jebel Qatrani escarpment and the Qasr el Sagha escarpment, north of Birket Qarun lake near Faiyum. The formation conformably overlies the Qasr el Sagha Formation and is topped by the Widan el Faras Basalt. The age of the formation has been subject to debate, but the most recent research indicates that it covers both the latest parts of the Eocene and the Early Oligocene, spanning over the boundary between these two time periods.
The Qasr el Sagha Formation is a geological formation located in Egypt. The formation is part of the Wadi El Hitan World Heritage Site. The Qasr el Sagha Formation overlies the Birket Qarun Formation and is overlain by the Gebel Qatrani Formation. The sandstones and shales of the formation were deposited in a deltaic to shallow marine environment. It dates to the Late Eocene.
Protocetidae, the protocetids, form a diverse and heterogeneous group of extinct cetaceans known from Asia, Europe, Africa, South America, and North America.
Saghacetus is an extinct genus of basilosaurid early whale, fossils of which have been found in the Upper Eocene Qasr el Sagha Formation, Egypt.
Cordichelys is an extinct genus of podocnemidid turtle. It was around during the Eocene. Fossils of this turtle have been discovered at Wadi El Hitan as of November 2020.
Protosiren eothene is a species of Lutetian sirenian, found in the upper part of the Habib Rahi Formation, Pakistan.
Makaracetus is an extinct protocetid whale, the remains of which were found in 2004 in Lutetian layers of the Domanda Formation in the Sulaiman Range of Balochistan, Pakistan.
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.
Eocetus is an extinct protocetid early whale known from the early-late Eocene Giushi Formation in Gebel Mokattam, outside Cairo, Egypt. Fossil remains have also been discovered in the Aridal Formation of the Sahara Desert in southwestern Morocco.
The Sath El-Hadid Formation, translating to "Iron Surface" in Arabic "سطح الحديد", is a geological formation in Egypt characterized by a nummulitic limestone bank containing large and small Nummulites. Introduced into the stratigraphy of the south Fayum area by Iskander in 1943, this formation is significant in the middle Eocene (Bartonian).
The Birket Qarun Formation is an Eocene aged formation in Egypt. It is part of the famous Wadi al Hitan. Notable fossils include the ancient whales Basilosaurus and Dorudon as well as sirenians Eotheroides and Eosiren. It also contains the teeth of various sharks and reptiles. The area was likely a mix of both marine and freshwater area with many freshwater deposits being found alongside a marine influence from the Tethys Sea. Fossils here also preserve a shallow marine nursery for the whale Dorudon and it seems that this area would have also been the site of active predation from Basilosaurus as it attacked the newly born Dorudon calves.
The Fayyum is a region and an important fossil Lagerstätte in northern Egypt. The region comprises the Fayyum Basin, which is intensively used for agriculture, and adjoining areas; the important areas of discovery are mostly north and west of Lake Qarun. The Wadi al-Hitan, known for its numerous whale fossils and since 2005 UNESCO World Natural Heritage Site, forms the south-western end. The deposits of the Fayyum belong to various geological formations. They are mainly composed of limestone, siltstone and sandstone. The lower sections consist of marine sediments, while the upper, continental sediments were formed in a coastal landscape. The formation period ranges from the Middle to the Upper Eocene to the Lower Oligocene, which corresponds to an age of around 41 to 28 million years ago. The entire sedimentary complex is overlain by basalt, which dates back to volcanic activity around 24 million years ago.