Stomatal ontogeny is often inferred but rarely documented for extinct fossil plants because it requires observations from young leaves that are rarely preserved as fossils. The discovery of several very young leaves of the Jurassic plant Sagenopteris (Caytoniales) in the Mecsek Mountains (southern Hungary) in a good state of preservation provides the opportunity for studying the stomatal ontogenesis of this genus. The specimens show perigenous anomocytic stomata. This feature confirms the evolutionarily high position of Sagenopteris among fossil gymnosperms and supports the opinion that the ancestors of angiosperms and some groups of pteridosperms might be closely related. Such clear examples of stomatal development have not previously been documented for fossil material.

中文翻译：

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匈牙利 Liassic Pteridosperm Sagenopteris (Caytoniales) 的气孔个体发育和结构

气孔个体发育通常被推断为已灭绝的化石植物，但很少被记录下来，因为它需要对很少被保存为化石的幼叶进行观察。在 Mecsek 山脉（匈牙利南部）发现了几片保存良好的侏罗纪植物 Sagenopteris (Caytoniales) 的幼叶，为研究该属的气孔个体发生提供了机会。标本显示近生的单核细胞气孔。这一特征证实了 Sagenopteris 在化石裸子植物中的进化地位，并支持被子植物的祖先与某些蕨类植物群可能密切相关的观点。这种气孔发育的明显例子以前没有记录在化石材料中。