No great extinction or burst of diversity separated the Cretaceous
from the Jurassic Period that had preceded it.
If there are no strong elements, some key feature are:
- flower plants
- diatoms in the oceans
Perhaps the most important of these events, at least for terrestrial
life, was the first appearance of the flowering plants, also called
the angiosperms or Anthophyta. First appearing in the Lower Cretaceous
around 125 million years ago, the flowering plants first radiated in
the middle Cretaceous, about 100 million years ago.
The source article also states:
Early angiosperms did not develop shrub- or tree-like morphologies,
but by the close of the Cretaceous, a number of forms had evolved that
any modern botanist would recognize. The angiosperms thrived in a
variety of environments such as areas with damper climates, habitats
favored by cycads and cycadeoids, and riparian zones. High southern
latitudes were not invaded by angiosperms until the end of the
Cretaceous. Ferns dominated open, dry and/or low-nutrient lands.
Typical Jurassic vegetation, including conifers, cycads, and other
gymnosperms, continued on into the Lower Cretaceous without
significant changes. At the beginning of this period, conifer
diversity was fairly low in the higher latitudes of the Northern
Hemisphere, but by the middle of the period, species diversification
was increasing exponentially. Swamps were dominated by conifers and