Based on palynological data, angiosperm dominance is achieved in the Turonian. Cycadophytes begin a decline in diversity before angiosperms become dominant, and the opening of this ecological niche may have provided the opportunity for angiosperms to diversify. Patterns of Diversification First angiosperms appear in low numbers in the Barremian. Large trees are known for the first time in the early-middle Albian. Mid-Albian flowering plants occur in higher middle latitudes and were locally dominant.
Diversity equals that of ferns and other groups.
At this time, nearly all major physiognomic foliage types can be found. There also appear to be strong latitudinal gradients in leaf types established by the Mid-Cenomanian. Arctic megafloras are dominated by broadleaved deciduous forests, the distribution of which was probably controlled by winter darkness and possibly freezing temperatures. Cenomanian to Coniacian assemblages show a rich and diverse conifer assemblage in which there is evidence for increasing diversity of angiosperms. Palms first appear in the Santonian in eastern North America and extend their range into higher middle latitudes and other monocots have been documented.