Monocots
The fossil record of monocots is known primarily from fossil pollen; their evolutionary history has not been well understood. There are a number of well-preserved leaves from the Cretaceous which appear to be monocots, but these cannot be placed definitively with any one group. It is not until the end of the Cretaceous (Maastrichtian) that recognizable fossils have been found; these include gingers, palms, and Dioscorea.
The sparse fossil record of most monocot groups may in part be due to the fact that monocots are primarily tropical, and most paleobotanists have collected in temperate and arctic regions. It is also true that leaves are found more frequently than other parts, and that many monocot groups are difficult to tell apart based solely on their leaves.
Diversity
Order Acorales
Order Alismatales
Order Asparagales
Order Dioscoreales
Order Liliales
Order Pandanales
Order Petrosaviales
Order Dasypogonaceae
Order Arecales
Order Commelinales
Order Poales
Order Zingiberales
Classification
└Lilianae
Geologic Range
Late Cretaceous - present
Additional Reading
The aquatic origins of monocots (Science 2018)