檢視异甲亚纲的原始碼

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'''异甲亚纲'''又名鳍甲亚纲Pteraspidomorpha，这是一类最古老而又为数众多的原始脊椎动物，其特征是头胸部为数块骨板所包围，骨板内缺少像头甲鱼那样的真正骨细胞构造；躯体常被以菱形鳞片；无中鳍和偶鳍；反歪型尾；口腹位或端腹位；眼靠前而侧位；无背鼻孔；鳃区常被一排鳃板所掩盖，由总鳃孔与外界相通。<ref>[http://www.cas.cn/syky/202108/t20210803_4800923.shtml 古脊椎所在盔甲鱼类早期演化研究中取得进展]中国科学院</ref>