The monocots are considered to form a [[monophyletic]] group arising early in the history of the [[flowering plant]]s. The earliest fossils presumed to be monocot remains date from the [[Cretaceous|early Cretaceous]] period.
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monocotyledons are related to each other).
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Taxonomists have considerable latitude in naming this group, as the monocots are a group above the rank of family. Article 16 of the ''[[ICBN]]'' allows either a [[descriptive botanical names|descriptive name]] or a name formed from the name of an included family.
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[[Image:Monocot_vs_dicot_crop_Pengo.jpg|thumb|Grass sprouting on left (a monocot), showing a single cotyledon. Compared to a dicot (right)]]
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Historically, the monocotyledons were named:
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* [[Monocotyledoneae]] in the [[de Candolle system]] and the [[Engler system]].
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* [[Monocotyledones]] in the [[Bentham & Hooker system]] and the [[Wettstein system]]
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* class [[Liliopsida]] in the [[Takhtajan system]] and the [[Cronquist system]].
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* subclass [[Liliidae]] in the [[Dahlgren system]] and the [[Thorne system (1992)]].
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* [[clade]] [[monocots]] in the [[APG system]] and the [[APG II system]].
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Each of the systems mentioned above use their own internal taxonomy for the group. The monocotyledons are famous as a group that is extremely stable in its outer borders (it is a well-defined, coherent group), while in its internal taxonomy is extremely unstable (historically no two authoritative systems have agreed with each other on how the monocotyledons are related to each other).