''Eotheroides'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

sirenian 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 Sirenia currently comprise two distinct f ...

. It is an early member of the family

Dugongidae Dugongidae is a family in the order of Sirenia. The family has one surviving species, the dugong (''Dugong dugon''), one recently extinct species, Steller's sea cow (''Hydrodamalis gigas''), and a number of extinct genera known from fossil rec ...

, which includes the extant

dugong The dugong (; ''Dugong dugon'') is a marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest m ...

. Fossils have been found from

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

, and

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

. ''Eotheroides'' was first described by

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Owe ...

in 1875 under the name ''Eotherium'', which was replaced by the current name in 1899. Based on

endocranial cast An endocast is the internal cast of a hollow object, often referring to the cranial vault in the study of brain development in humans and other organisms. Endocasts can be artificially made for examining the properties of a hollow, inaccessible sp ...

s, ''Eotheroiodes'' had a smaller endocranial volume than other contemporaneous sirenians such as ''

Protosiren ''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 (South Carolina, No ...

''. Unlike extant sirenians, ''Eotheroides'' possesses a

tentorium cerebelli The cerebellar tentorium or tentorium cerebelli (Latin for "tent of the cerebellum") is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes. Structure The cerebellar tentorium is an arche ...

, which appears as a distinct transverse groove on the skull.

Species

The type species, ''E. aegyptiacum'', is known from the

Lutetian The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Midd ...

Mokattam Limestone The Mokattam ( arz, المقطم , also spelled Muqattam), also known as the Mukattam Mountain or Hills, is the name of a range of hills and a suburb in them, located in southeastern Cairo, Egypt. Etymology The Arabic name ''Mokattam'' ...

Cairo Cairo ( ; ar, القاهرة, al-Qāhirah, ) is the capital of Egypt and its largest city, home to 10 million people. It is also part of the largest urban agglomeration in Africa, the Arab world and the Middle East: The Greater Cairo metro ...

, Egypt. Another species, ''E. lambondrano'', was recently named on the basis of material found from

Middle Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "dawn ...

nearshore marine deposits in the

Mahajanga Basin Mahajanga (French: Majunga) is a city and an administrative district on the northwest coast of Madagascar. The city of Mahajanga (Mahajanga I) is the capital of the Boeny Region. The district (identical to the city) had a population of 220,629 ...

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''. Described in 2009, ''E. lambondrano'' is the first pre-

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

mammal named from Madagascar, being known from an 80-million-year gap in the island's fossil record. Several other species have been named, including ''E. babiae'' from India, ''E. majus'', ''E. clavigerum'' and ''E. sandersi'' from Egypt, and ''E. waghapadarensis'', also from India. ''E. majus'' was based on a single upper molar, which was never catalogued and is now lost; it has been considered a senior subjective synonym of ''E. aegyptiacum''.

Paleobiology

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. ''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,

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

ns, and

sea turtles Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...

, which suggests that the locality is representative of a coastal or estuarine environment.

References

External links

Prehistoric Pygmy Sea Cow Discovered in Madagascar

''Eotheroides''
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

{{Taxonbar, from=Q1452411 Eocene sirenians Eocene mammals of Africa Transitional fossils Taxa named by Édouard Louis Trouessart Fossil taxa described in 1905 Prehistoric placental genera

Species

Paleobiology

References

Further reading

External links