Heterostraci

（重定向自Heterostracan）

Among the most primitive heterostracans are tolypelepids (top right). Most heterostracans are pteraspidiforms, such as the pteraspidids (bottom right), doryaspidids (bottom left) and the huge psammosteids (top left), which are the youngest known members of the group.[1]

Heterostraci ("Different scales") is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. The first identifiable heterostracans appear in the fossil record during the early Silurian, and all, save for the Psammosteids, became extinct by the start of the late Devonian. This last group of heterostracans died out in the extinction event at the end of the Devonian.

单词	Heterostracan
释义	Heterostracan 原声例句 PBS地球-动物趣闻 And heterostracans, osteostracans and placoderms have been found in both salty AND fresh water environments. 在咸水和淡水环境中都发现了 heterostracans、osteostracans 和 placoderms。 PBS地球-动物趣闻 And scientists have seen signs of those changes in the armor of heterostracans, osteostracans and placoderms. 科学家们已经看到了异类动物、骨类动物和盾皮动物的盔甲发生这些变化的迹象。英语百科 Heterostraci （重定向自Heterostracan） Heterostraci ("Different scales") is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. The first identifiable heterostracans appear in the fossil record during the early Silurian, and all, save for the Psammosteids, became extinct by the start of the late Devonian. This last group of heterostracans died out in the extinction event at the end of the Devonian.
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