| 词条 | Cuesta sea cow |
| 释义 |
| fossil_range = Late Pliocene to early Quaternary {{Fossil range|3.6|2.6}} | name = Cuesta sea cow | regnum = Animalia | phylum = Chordata | classis = Mammalia | ordo = Sirenia | familia = Dugongidae | subfamilia = †Hydrodamalinae | genus = †Hydrodamalis | species = †H. cuestae | species_authority = Domning, 1978 | synonyms = ?†H. spissa Furusawa, 1988 }} The Cuesta sea cow (Hydrodamalis cuestae) is an extinct herbivorous marine mammal, and the direct ancestor of the Steller's sea cow (Hydrodamalis gigas). They reached up to {{convert|9|m|ft}} in length, making them among the biggest sirenians to have ever lived. They were first described in 1978 by Daryl Domning when fossils in California were unearthed. Its appearance and behavior are largely based on that of the well-documented Steller's sea cow, who, unlike the Cuesta sea cow, lived into modern times and was well described. Taxonomy and extinction{{Cladogram|align=left|title=Relations within Sirenia|caption=Based on a 2004 study by Hitoshi Furusawa[1]|cladogram={{clade|style=font-size:100%;line-height:100% |label1=Sirenia |1={{clade |1={{clade |label1=Dugongidae |1={{clade |1={{clade |label1=†Halitherium |1={{clade |1=†H. schinzii |2=†H. alleni }} |2={{clade |1={{clade |label1=†Dusisiren |1={{clade |1=†D. jordani |2=†D. reinharti |3=†D. dewana |4=†D. takasatensis }} }} |3={{clade |label1=†Hydrodamalis |1={{clade |1=†H. gigas |2={{clade |1=†H. cuestae |2=†H. spissa }} }} }} }} }} |2={{clade |label1=Dugong |1={{clade |1=Dugong dugon }} }} }} }} |2={{clade |1={{clade |label1=Trichechidae |1={{clade |label1=Trichechus |1={{clade |1=Trichechus inunguis |2=Trichechus manatus |3=Trichechus senegalensis }} }} }} }} }} }} }} The fossils of the Cuesta sea cow were first discovered in the Late Pliocene sediment formations of Pismo Beach, California in 1978, and following finds of the species were unearthed in California.[2] In 1988, fossils of sea cows were discovered in Hokkaido, but were originally assigned to the Takikawa sea cow (H. spissa),[3] a newly described species, but this is thought of by some scientists as a synonym of H. cuestae. It is uncertain whether or not H. spissa was simply a local variant of H. cuestae or a completely separate lineage.[3] The Steller's sea cow was apparently a direct descendant of the Cuesta sea cow.[4] The Cuesta sea cow went extinct around 2 and a half million years ago. The disappearance of the Cuesta sea cow was likely linked to the onset of the Quaternary glaciation. Its main food source of seagrasses, due to the cooling of the oceans, declined to a point where it could no longer support their population. As well as this, the sea cows themselves were not adapted to the cold, and those that were probably gave rise to the Steller's sea cow.[2] Biology and behaviorThe Cuesta sea cow, like the Steller's sea cow, was probably gregarious and lived in small family groups. The bones were dense and served as a sort of ballast to prevent floating, probably so that they could feed on bottom-dwelling sea grasses. Sea grasses were their preferred food source. They most likely 'walked' along the shallow seafloor using their front limbs, using their powerful tail fin for propulsion. It has been speculated that, like the Steller's sea cows, the front limbs were used as holdfasts. The Cuesta sea cow was among the largest of the sirenians to have ever lived, reaching up to {{convert|9|m|ft}} in length and possibly {{convert|10|t|ST}}. The body was fusiform, being tapered at both the head and the tail.[2][5] See also{{Portal|Mammals|Marine life|Paleontology}}
References1. ^{{cite journal|url=http://www.bioone.org/doi/full/10.2517/prpsj.8.91|first=Hitoshi|last=Furusawa|year=2004|title=A phylogeny of the North Pacific Sirenia (Dugongidae: Hydrodamalinae) based on a comparative study of endocranial casts|journal=Paleontological Research|volume=8|number=2|pages=91–98|doi=10.2517/prpsj.8.91}} {{Taxonbar|from=Q9295375}}2. ^1 2 {{cite journal| first=Daryl P.|last=Domning|year=1978|title=An Ecological Model for Late Tertiary Sirenian Evolution in the North Pacific Ocean|journal=Systematic Zoology|volume=25|number=4|pages=352–362|jstor=2412510|doi=10.2307/2412510}} 3. ^1 {{cite book|last=Furusawa|first=H.|year=1988|title=A new species of hydrodamaline Sirenia from Hokkaido, Japan|publisher= Takikawa Museum of Art and Natural History|pages=1–73}} 4. ^{{cite book|url={{Google books|plainurl=yes|id=7pQgAwAAQBAJ|page=76}}|first=Helene|last=Marsh|first2=Thomas J.|last2=O'Shea|first3=John E. |last3=Reynolds III|year=2011|title=Ecology and Conservation of the Sirenia: Dugongs and Manatees|chapter=Steller's sea cow: discovery, biology and exploitation of a relict giant sirenian|publisher=Cambridge University Press |location=New York|pages=18–35|ISBN=978-0-521-88828-8}} 5. ^{{Cite web |url=http://age-of-mammals.ucoz.ru/index/hydrodamalis_cuesta/0-36 |title=Hydrodamalis cuestae |year=2013 |publisher=Age of Mammals |language=Russian |archive-url=https://archive.is/20130417221955/http://age-of-mammals.ucoz.ru/index/hydrodamalis_cuesta/0-36 |archive-date=17 April 2013 |access-date=2 September 2016 |deadurl=yes |df= }} 4 : Pleistocene sirenians|Extinct mammals|Extinct mammals of Asia|Fossil taxa described in 1978 |
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