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Pakicetus

 
Pakicetus

 
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Pakicetus
 
 
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Pakicetus is a genus of extinct cetaceans found in the early Eocene
Eocene

The Eocene Geologic time scale is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era....
 (55.8 ± 0.2 - 33.9 ± 0.1 Ma
Annum

Annum is one form of the Latin noun meaning year, not a form normally used for derivatives in modern languages: the accusative case Grammatical number of the second declension grammatical gender noun annus , anni ....
) of Pakistan
Pakistan

Pakistan , officially the Islamic Republic of Pakistan, is a country located in South Asia and borders Central Asia and the Middle East. It has a 1,046 kilometre coastline along the Arabian Sea and Gulf of Oman in the south, and is bordered by Afghanistan and Iran in the west, India in the east and People's Republic of China in th...
, hence their name. The strata where the fossil
Fossil

Fossils are the preserved remains or trace fossil of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous Rock formations and sedimentary rock layers is known as the fossil record....
s were found was then part of the coast of the Tethys Sea.

The first fossil, a lone skull, was thought to be a mesonychid
Mesonychid

Mesonychia are an extinct order of medium to large-sized carnivore mammals that were closely related to artiodactyls , and to cetaceans . A few experts unite Mesonychia with the whales to form the clade "Cete." They first appeared in the Early Paleocene and went into a sharp decline at the end of the Eocene and died out entirely when the la...
, but Gingerich and Russell recognized it as an early cetacean from characteristic features of the inner ear
Inner ear

The inner ear is the labyrinth , a system of passages comprising two main functional parts:* the organ of hearing, or cochlea* and the vestibular apparatus, the organ of balance that consists of three semicircular canals and the Vestibule of the ear....
, found only in cetaceans: the large auditory bulla is formed from the ectotympanic bone only.






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Encyclopedia


Pakicetus is a genus of extinct cetaceans found in the early Eocene
Eocene

The Eocene Geologic time scale is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era....
 (55.8 ± 0.2 - 33.9 ± 0.1 Ma
Annum

Annum is one form of the Latin noun meaning year, not a form normally used for derivatives in modern languages: the accusative case Grammatical number of the second declension grammatical gender noun annus , anni ....
) of Pakistan
Pakistan

Pakistan , officially the Islamic Republic of Pakistan, is a country located in South Asia and borders Central Asia and the Middle East. It has a 1,046 kilometre coastline along the Arabian Sea and Gulf of Oman in the south, and is bordered by Afghanistan and Iran in the west, India in the east and People's Republic of China in th...
, hence their name. The strata where the fossil
Fossil

Fossils are the preserved remains or trace fossil of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous Rock formations and sedimentary rock layers is known as the fossil record....
s were found was then part of the coast of the Tethys Sea.

The first fossil, a lone skull, was thought to be a mesonychid
Mesonychid

Mesonychia are an extinct order of medium to large-sized carnivore mammals that were closely related to artiodactyls , and to cetaceans . A few experts unite Mesonychia with the whales to form the clade "Cete." They first appeared in the Early Paleocene and went into a sharp decline at the end of the Eocene and died out entirely when the la...
, but Gingerich and Russell recognized it as an early cetacean from characteristic features of the inner ear
Inner ear

The inner ear is the labyrinth , a system of passages comprising two main functional parts:* the organ of hearing, or cochlea* and the vestibular apparatus, the organ of balance that consists of three semicircular canals and the Vestibule of the ear....
, found only in cetaceans: the large auditory bulla is formed from the ectotympanic bone only. This suggests that it is a transitional species between extinct land mammals and modern cetaceans.

Complete skeletons were discovered in 2001, revealing that Pakicetus was primarily a land animal, about the size of a wolf, and very similar in form to the related mesonychid
Mesonychid

Mesonychia are an extinct order of medium to large-sized carnivore mammals that were closely related to artiodactyls , and to cetaceans . A few experts unite Mesonychia with the whales to form the clade "Cete." They first appeared in the Early Paleocene and went into a sharp decline at the end of the Eocene and died out entirely when the la...
s.

See also

  • Evolution of cetaceans
    Evolution of cetaceans

    The cetaceans are descendants of land-living mammals. Their terrestrial origins are specifically indicated by:* Their need to breathe air from the surface;...