Utilisateur:Ygdrasil/macrauchenia
le macrochenia est un animal qui n'est apparenté a aucun animal actuel
Macrauchenia . Les Litopternes
Si extérieurement, Macrauchenia ressemble à un chameau, son squelette est très différent. Les vertèbres suggèrent qu’il devait avoir une petite bosse au-dessus du garrot.
Cet ongulé mi-cheval, mi-chameau, vivait dans les plaines herbeuses. Son long cou lui permettait de voir de loin les éventuels prédateurs. Ses mâchoires étaient pourvues de 44 grosses prémolaires et molaires.
D'autres Litopternes
Diadiaphorus ressemblait plus à un cheval. Il possédait de longues pattes et un pied ne reposant que sur un seul orteil. Toutefois ses dents n'étaient pas aussi spécialisées pour brouter.
Certains litopternes étaient des coureurs rapides. La plupart comme Macrauchenia et Theosodon couraient sur trois doigts. Mais, d'autres comme Diadiaphorus et Thoatherium développèrent des membres plus fins qui se terminaient par un seul doigt.
SSSS http://www.dinosoria.com/macrauchenia.htm
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Litopterna ("simple ankles") is an extinct order of fossil hoofed mammals (ungulates) from the Tertiary period that displays toe reduction. Three-toed, and even a one-toed horselike form developed. This order, known only from South America, was common and varied in early faunas and persisted, in decreasing variety, into the Pleistocene. Early forms are near the condylarths, to such an extent that the litopterns might be considered merely as surviving and diversely specialized condylarths. They are suspected of being descended from South American condylarths, and therefore to have the same source as the latter. However, there is a growing number of scientists who believes the Litopterna (together with other South-American ungulates) originated completely independent from the other ungulates, thus are unrelated to the condylarths. They proposed a new clade to contain these groups: the Meridiungulata. Macrauchenia was the youngest genus of litopterns, and was the only litoptern group to survive the Great American Interchange; it died out during the Pleistocene. The Litopterna, like the notoungulates and pyrotheres, are examples of ungulate mammals that arose relatively independently in "splendid isolation" on the island continent of South America. Like Australia, South America was isolated from all other continents following the breakup of Gondwana. During this period of isolation, unique mammals evolved to fill ecological niches similar to other mammals elsewhere. The Litopterna occupied ecological roles as browsers and grazers similar to horses and camels in Laurasia.
Families of Litopterns
modifier- Order Litopterna - Litopterans (all members of the order extinct South American forms)
- Family Protolipternidae - incertae sedis
- Superfamily Macrauchenioidea
- Family Macraucheniidae
- Family Notonychopidae
- Family Adianthidae
- Superfamily Proterotherioidea
- Family Proterotheriidae
Proposed ancestry
modifierThis tree shows a proposed ancestry of several mammals including the Litopterna (walvis=whale, zwijn=pig, paard=horse):
References
modifier- McKenna, M. C, and S. K. Bell. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp.
External links
modifier- An artist's rendition of a Macrauchenia, a representative genus of the Litopterna. Retrieved from the Red Académica Uruguaya megafauna page.
