The appearance of evergreen sclerophyllous Quercus with entire leaves might have occurred earlier than those with toothed leaves.Deciduous, urticoid-leaved oak fossils (Quercus subg.Quercus sect.

• 三棱栎属、栲属和石栎属的化石在老第三纪出现于北美和欧洲的事实说明，北美、欧洲和东亚在老第三纪时有一个相通的壳斗科植物区系。