Aetiocetus
Encyclopedia
Aetiocetus is an extinct genus of baleen whale
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...

 that lived 25 million years ago, in the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

 period. Its fossils have been found in the North Pacific, around Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

. It was first named by Douglas Emlong
Douglas Emlong
Douglas Ralph Emlong was an amateur fossil collector from the Oregon Coast in the northwestern United States. His collections contributed to the discovery and description of numerous extinct marine mammal species, many of which are ancestral to extant groups...

 in 1966 and currently contains four species, A cotylalveus, A. polydentatus, A. tomitai, and A. weltoni.

Description

Aetiocetus is a transitional fossil
Transitional fossil
A transitional fossil is any fossilized remains of a lifeform that exhibits characteristics of two distinct taxonomic groups. A transitional fossil is the fossil of an organism near the branching point where major individual lineages diverge...

 between early whales and the modern whales, its blowhole being located halfway up its snout rather than at the top of its head. It is also one of the earliest-known baleen whales. The genus, though more cranially reminiscent of archaic whales, with its pronounced snout and flat cranium, had a loose jaw like later baleen whales. Aetiocetus skulls have also shown that the animal bore a full set of teeth, as well as baleen. The skulls contain about forty-four teeth, which consist of cusped molars, curved canine
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

s, and incisors. Aetiocetus most likely fed on fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 and crustaceans.

Douglas Emlong originally classified it in the extinct whale suborder Archaeoceti
Archaeoceti
Archaeocetes, or "ancient whales", are a paraphyletic group of cetaceans that gave rise to the modern cetaceans.The archaeocetes were once thought to have evolved from the mesonychids, based on dental characteristics...

, because of its teeth. However, when Van Valen analyzed it in 1968, he moved the genus to the suborder Mysticeti due to its derived pattern of bone telescoping.

Species

  • A. cotylalveus, type species
    Type species
    In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

    , Emlong
    Douglas Emlong
    Douglas Ralph Emlong was an amateur fossil collector from the Oregon Coast in the northwestern United States. His collections contributed to the discovery and description of numerous extinct marine mammal species, many of which are ancestral to extant groups...

    , 1966
  • A. polydentatus, Barnes, Kimura, Furusawa & Sawamura, 1995
  • A. tomitai, Barnes, Kimura, Furusawa & Sawamura, 1995
  • A. weltoni, Barnes, Kimura, Furusawa & Sawamura, 1995. An analysis of this species revealed similar palatal nutrient foramina to those that house vessels that feed modern genera of mysticetes.

Sister Taxa

  • Ashorocetus
    Ashorocetus
    Ashorocetus is an extinct genus of Aetiocetidae. It was first named by L.G. Barnes et al. in 1995, and contains one species, A. eguchii.-Sister Taxa:*Aetiocetus*Chonecetus*Morawanocetus*Willungacetus-Sources:...

  • Chonecetus
    Chonecetus
    Chonecetus is an extinct genus of Neocene Aetiocetidae that lived in the Oligocene period. Its fossils have been found in Canada, in the northeast Pacific. It was first named by L.S. Russell in 1968, and contains two species, C. sookensis and C. goedertorum...

  • Morawanocetus
    Morawanocetus
    Morawanocetus is an extinct genus of Aetiocetidae from the Oligocene period. Its fossils have been found in the North Pacific. It was first named by Barnes et al. in 1995, and contains one species, M. yabukii...

  • Willungacetus
    Willungacetus
    Willungacetus is an extinct genus of Aetiocetidae which existed during the Oligocene period. Its fossils have been found in Australia. It was first named by Pledge in 2005, though he had discovered it at Port Willunga in 2001, and contains one species, W. aldingensis...


Further reading

  • At the Water's Edge : Fish with Fingers, Whales with Legs, and How Life Came Ashore but Then Went Back to Sea by Carl Zimmer
    Carl Zimmer
    Carl Zimmer is a popular science writer and blogger, especially regarding the study of evolution and parasites. He has written several books and contributes science essays to publications such as The New York Times and Discover...

    ISBN 0-684-83490-1
  • Marine Mammals: Evolutionary Biology by Annalisa Berta, James L. Sumich, and Kit M. Kovacs
  • In Search of Ancient Oregon: A Geological and Natural History by Ellen Morris Bishop
  • Whales of the West Coast by David A E Spalding
  • Encyclopedia of Marine Mammals by William F. Perrin, Bernd Wursig, and J. G.M. Thewissen
  • Aquagenesis: The Origin and Evolution of Life in the Sea by Richard Ellis
  • The New Encyclopaedia Britannica By Encyclopaedia Britannica, inc, Robert McHenry ISBN 0-85229-633-9
  • Grzimek's Animal Life Encyclopedia by Bernhard Grzimek, Neil Schlager, Donna Olendorf, and Melissa McDade, of the American Zoo and Aquarium Association. ISBN 0-7876-5791-3

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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