| 翻訳と辞書 |
| Thylacocephala ： ウィキペディア英語版 |
Thylacocephala
The Thylacocephala (from the Greek or ', meaning "pouch", and or ' meaning "head") are a unique group of extinct arthropods, with possible crustacean affinities. As a class they have a short research history, having been erected in the early 1980s. They typically possess a large, laterally flattened carapace that encompasses the entire body. The compound eyes tend to be large and bulbous, and occupy a frontal notch on the carapace. They possess three pairs of large raptorial limbs, and the abdomen bears a battery of small swimming limbs. The earliest thylacocephalan fossil is thought to date from the lower Cambrian, while the class has a definite presence in Lower Silurian marine communities. As a group, the Thylacocephala survived to the Upper Cretaceous. Beyond this, there remains much uncertainty concerning fundamental aspects of the thylacocephalan anatomy, mode of life, and relationship to the Crustacea, with whom they have always been cautiously aligned.
==Research history==
The Thylacocephala are relatively young as a class, yet species now included within the group were first described at the turn of the century. These were typically assigned to the phyllocarids despite an apparent lack of abdomen and appendages. In 1982/83, three research groups independently created higher taxa to accommodate new species. Based on a specimen from northern Italy, Pinna ''et al.'' designated a new class,〔 Thylacocephala, while Secrétan – studying ''Dollocaris ingens'', a species from the La Voulte-sur-Rhône konservat-lagerstätte in France – erected the class Conchyliocarida. Briggs & Rolfe, working on fossils from Australia's Devonian deposits were unable to attribute certain specimens to a known group, and created an order of uncertain affinities, the Concavicarida, to accommodate them.〔 It was apparent the three groups were in fact working on a single major taxon (Rolfe noted disagreements over interpretation and taxonomic placement largely resulted from a disparity of sizes and differences in preservation.) The group took the name Thylacocephala by priority, with Concavicarida and Conchyliocarida subjugated to orders, erected by Rolfe,〔 and modified by Schram.〔
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「Thylacocephala」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.
|
|