| 翻訳と辞書 |
| Distichophytum ： ウィキペディア英語版 |
Distichophytum
''Distichophytum'' is a genus of extinct vascular plants of the Late Silurian (Ludfordian) to Early Devonian (Emsian), around . The genus has a tangled taxonomic history, also being known as ''Bucheria'' and ''Rebuchia'' (see below).
==Description==
The genus was first discovered as fossils of Early Devonian age (Pragian or Siegenian to Emsian, ), consisting of isolated spikes of sporangia (spore-forming organs) found at Beartooth Butte, Wyoming, United States of America. Specimens of ''D. ovata'' with sporangia attached to stems were later found at the same location. The base of the plant remains unknown; the known part was about 8.5 cm high. The sporophyte consisted of narrow leafless stems (axes) 1.5 to 2.0 mm in diameter, which branched dichotomously. Stems which did not bear sporangia ended in blunt points; fertile branches bore compact one-sided spikes of up to 20 laterally attached sporangia, more-or-less opposite. The sporangia were kidney-shaped (reniform) and had short stalks around 1.5 mm long which curved so that all the sporangia were on one side of the stem. The sporangia split (dehisced) distally into two equal parts in order to release the unornamented spores.〔, p. 258〕 Specimens from the Pragian flora of Bathurst Island, Nunavut, Canada, were later also assigned to this species, although their sporangia were smaller.〔
A second possible species, ''D. mucronatum'', has narrower, less branched stems and smaller, somewhat differently shaped sporangia than ''D. ovata''. Hueber considered the differences in sporangial shape were caused by compression and that the other differences were too small to warrant a different species;〔 Schweitzer put the two in the same genus but as different species.〔, cited in 〕 A third possible species was discovered in sediments from Bathurst Island, Nunavut, Canada, from the Late Silurian (Ludfordian, ); it was not assigned a species name as poor preservation obscured the sporangial shape.〔
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「Distichophytum」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.
|
|