| 翻訳と辞書 |
mesonychid
Mesonychia ("middle claws") is an extinct taxon of small- to large-sized carnivorous digitigrade ungulates related to the cetartiodactyls. Mesonychids first appeared in the early Paleocene, went into a sharp decline at the end of the Eocene, and died out entirely when the last genus, ''Mongolestes'', became extinct in the early Oligocene.
Mesonychids probably originated in Asia, where the most primitive mesonychid, ''Yangtanglestes'', is known from the early Paleocene. They were also most diverse in Asia, where they occur in all major Paleocene faunas. Since other carnivores, such as the creodonts and condylarths, were either rare or absent in these animal communities, mesonychids most likely dominated the large predator niche in the Paleocene of Asia.
One genus, ''Dissacus'', had successfully spread to Europe and North America by the early Paleocene. ''Dissacus'' was a jackal-sized carnivore that has been found all over the Northern Hemisphere, but its daughter genus, ''Ankalagon'', from the early to middle Paleocene of New Mexico, was far larger, growing to the size of a bear.[〕 Species of the later genus, ''Pachyaena'', entered North America by the earliest Eocene, where they evolved into huge species surpassing even ''Ankalagon'' in size. Mesonychids in North America were by far the largest predatory mammals during the early Paleocene to middle Eocene.]
==Characteristics==
The mesonychids bore a strong, albeit superficial, resemblance to wolves. Early mesonychids had five digits on their feet, which probably rested flat on the ground during walking (plantigrade locomotion), but later mesonychids had four digits that ended in tiny hooves on all of their toes and were increasingly well adapted to running. Like running members of the even-toed ungulates, mesonychids (''Pachyaena'', for example) walked on their digits (digitigrade locomotion).〔
These "wolves on hooves" were probably one of the more important predator groups (although they may have been scavengers) in the late Paleocene and Eocene ecosystems of Europe (which was an archipelago at the time), Asia (which was an island continent), and North America. Mesonychid dentition consisted of molars modified to generate vertical shear, thin blade-like lower molars, and carnassial notches, but no true carnassials. The molars were laterally compressed and often blunt, and were probably used for shearing meat or crushing bones. Many species are suspected of being fish-eaters, and the largest species are considered to have been scavengers.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「mesonychid」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|