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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Jamoytius ： ウィキペディア英語版 Jamoytius ''Jamoytius kerwoodi'' was a species of primitive, eel-like jawless fish that lived in the Silurian period. Long thought of as a "basal anaspid," ''J. kerwoodi'' is now recognized as the best-known member of the Hyperoartian order Jamoytiiformes. It had an elongated body, and is thought to have had, in comparison with relatives known from intact bodies like ''Euphanerops'', a dorsal fin and an anal fin near the posteriormost third of its body. Earlier reconstructions depict the creature as having side-fins running the length of its body, starting from behind the branchial openings to the tip of its tail: new research demonstrates that such "fins" are actually deformations of the bodywall as the corpse was being squished post-burial.〔 In life, ''J. kerwoodi'' resembled a lamprey with a very small mouth. Because the fossil had no teeth, teeth-like structures, nor suggestions of either in its mouth, it was not carnivorous like many modern lampreys. It was more likely to have been a filter-feeder or a detrius-feeder, possibly in the manner of larval lampreys. The fish had a cartilaginous skeleton, and a branchial basket resembling the cyclostomes - used to suggest that it was a near-ancestor to that clade. It is also the earliest known vertebrate with camera-type eyes. It also possessed weakly mineralised scales. ==History of research== ''Jamoytius'' was originally named by Errol White on the basis of two specimens (the generic name is a reference to J. A. Moy-Thomas〔Dawkins, Richard The Ancestor's Tale〕) and, at the time, it was considered to be the most basal vertebrate known. Since then, it has been reclassified by many workers as having many different affinities, such as an "unspecialized anaspid", or as a sister taxon to the lampreys,〔 its difficulty in classification due to difficulties in reconstructing the anatomy; it does not possess any usual chordate synapomorphies. Currently, ''J. kerwoodi'' is now placed in its own order Jamoytiiformes, together with ''Euphanerops'' and similar agnathans.〔 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「Jamoytius」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.