''Protocetus atavus'' ("first whale") is an extinct species of primitive cetacean 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 ...
. It lived during the middle
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' ...
period 45 million years ago. The first discovered protocetid, ''Protocetus atavus'' was described by based on a cranium and a number of associated vertebrae and ribs found in middle
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 ...
Tethyan marine limestone from Gebel Mokattam near Cairo, Egypt.
Description
''Protocetus'' are believed to have had a streamlined, whale-like body around long, but was probably primitive in some respects.
[Palmer D (ed.) (1999). ''The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals''. London: Marshall Editions. p. 230. .]
Many protocetids (like ''
Maiacetus
''Maiacetus'' ("mother whale") is a genus of early middle Eocene (c. 47.5 mya) cetacean from the Habib Rahi Formation of Pakistan.
Paleobiology
The genus contains a single species, ''Maiacetus inuus'', first described in 2009 on the basis of ...
'', ''
Rodhocetus
''Rodhocetus'' (from ''Rodho'', the geological anticline at the type locality, and ''cetus'', Latin for whale) is an extinct genus of protocetid early whale known from the Lutetian of Pakistan. The best-known protocetid, ''Rodhocetus'' is known ...
'') possessed well developed
innominates and hind limbs, often attached to the backbone with a
sacrum
The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30.
The sacrum situates at the upper, back part ...
. ''Protocetus'' are known to have had at least one sacral vertebrate,
[Gingerich P.D. (2010). "Cetacea". In Werdelin L & Sanders W.J. (eds.). ''Cenozoic mammals of africa''. Berkeley: University of California Press, p. 873–899] and likely possessed hind limbs and webbed toes.
The shape of the bones in the tails suggests that it may have had a tail fluke like modern whales.
The head of ''Protocetus'' measured about 0.6 meters long.
[Gingerich, Philip D.; Arif, Muhammad; Clyde, William C. (1995). "New Archaeocetes (Mammalia, Cetacea) from the middle Eocene Domanda Formation of the Sulaiman Range, Punjab (Pakistan)". ''Contributions from Museum of Paleontology, the University of Michigan''. 29 (11): p. 291–330] The jaws were long and lined with sharp
teeth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
. While it did not have a true
blowhole, the nostrils were placed further back on the head than in most land mammals.
Unlike the more primitive ''
Pakicetus
''Pakicetus'' is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to Pakistan during the Eocene, about 50 million years ago. It was a wolf-like animal, about to long, and lived in and around water where it a ...
'', the structure of the ears suggests that ''Protocetus'' was able to hear properly underwater, although it is unlikely that it could
echolocate. Similarly, it retained sufficient olfactory apparatus to have a good
sense of smell
The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste.
In humans, it ...
, although it probably relied more on its eyesight to find prey.
See also
*
Evolution of cetaceans
The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. Cetaceans are fully aquatic marine mammals bel ...
References
Notes
Sources
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Protocetidae
Prehistoric cetacean genera
Fossil taxa described in 1904
Paleogene mammals of Asia
Eocene mammals of Africa
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