已经灭绝的本内苏铁目是地质历史时期苏铁家族中的重要类群,出现于三叠纪,侏罗纪时期最为繁盛,早白垩世开始衰退,大部分于晚白垩世绝灭。本内苏铁目与现存苏铁具有许多相似的生活习性和外部特征,包括木本,茎圆柱形,叶羽状,多数类群茎干表面密布宿存的叶基,二歧分枝或不分枝。但同时具有与现生苏铁明显不同的特征,如生殖器官的位置与现生苏铁明显不同,位于叶基部或者茎干的分叉处,叶片表皮气孔器与现生苏铁明显不同,具有两个保卫细胞和2个与其平行排列的副卫细胞。世界范围内本内苏铁茎干化石报道主要来自北美、欧洲(英国、西班牙)、亚洲(印度、日本)等的中生代地层。长久以来,我国中生代地层发现的本内苏铁植物多数是叶片和生殖器官,而茎干非常少。![](http://tiebapic.baidu.com/forum/w%3D580/sign=e775f7177c01213fcf334ed464e636f8/5d56a29759ee3d6d3f9e440506166d224e4ade14.jpg?tbpicau=2024-09-14-05_e87f2f9e50c64cae27aa82064e256b40)
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