名稱 三葉蟲化石Name Trilobite Collection Plate地質年代 泥盆纪Geological Age Devonian描述 三葉蟲綱(學名:Trilobita)的動物通稱三葉蟲,是節肢動物門中已經滅絕的一綱。牠們最早出現於寒武紀,在古生代早期達到頂峰,此後逐漸減少至滅絕。最晚的三葉蟲(砑頭蟲目)於二億五千萬年前二疊紀結束時的生物集群滅絕中消失。三葉蟲的軀體分三個體段(tagmata):頭部由口前的兩個體節和口後的四個體節完全融合在一起組成,胸部由可以相互運動的體節組成,尾部由最後幾個羽尾扇和完全融合在一起的體節組成。最原始的三葉蟲尾部的體節構造相當簡單。三葉蟲的胸部非常靈活——化石的三葉蟲有時會像現今的地鱉一樣可以將身體卷在一起來保護自己。雖然三葉蟲只在背部有盔甲,但是它們的外骨骼還是相當沉重的,牠們的外骨骼是由甲殼素為主的蛋白質聯合方解石和磷化鈣等礦物組成的。不像其他節肢動物那樣能夠在蛻皮前重新吸收外骨骼中的大部分礦物,三葉蟲在蛻皮是將所有盔甲中的礦物全部拋棄,因此一隻三葉蟲可以留下多個良好地礦物化的外骨骼,這提高了三葉蟲化石的數量。Description Trilobite, any member of a group of extinct fossil arthropods easily recognized by their distinctive three-lobed, three-segmented form. Trilobites, exclusively marine animals, first appeared at the beginning of the Cambrian Period, about 542 million years ago, when they dominated the seas. Although they became less abundant in succeeding geologic periods, a few forms persisted into the Permian Period, which ended about 251 million years ago. Trilobites had three body lobes, two of which lay on each…
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