| 翻訳と辞書 |
phacopida
Phacopida ("Lens-face") is an order of trilobite that lived from the Ordovician to the Devonian. It is made up of a morphologically diverse group of related suborders.
The origin of the Phacopida order is uncertain. It comprises three suborders (Phacopina, Calymenina, and Cheirurina) which share a distinctive protaspis (developmental stage lacking segments) type. The Cheirurina and Calymenina retain a rostral plate (an apomorphy) but in virtually all Phacopina the free cheeks are yoked as a single piece. This sort of similarity in development suggests phylogenetic unity. The suborder Calymenina is the most primitive of the Phacopida order and shares some characteristics with the order Ptychopariida, though it is not included in the subclass Libristoma.
Phacopida had 8 to 19 thoracic segments and are distinguishable by the expanded glabella, short or absent preglabellar area, and schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina) eyes. Schizochroal eyes are compound eyes with up to around 700 separate lenses. Each lens has an individual cornea which extended into a rather large sclera.
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「phacopida」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.
|
|