Cretaceous
Flora

Flowering plants (angiosperms) make up around 90% of living plant species today. Prior to the rise of angiosperms, during the Jurassic and the Early Cretaceous, the higher flora was dominated by gymnosperm groups, including cycads, conifers, ginkgophytes, gnetophytes and close relatives, as well as the extinct Bennettitales. Other groups of plants included pteridosperms or "seed ferns", a collective term that refers to disparate groups of extinct seed plants with fern-like foliage, including groups such as Corystospermaceae and Caytoniales. The exact origins of angiosperms are uncertain, although molecular evidence suggests that they are not closely related to any living group of gymnosperms.

The earliest widely accepted evidence of flowering plants are monosulcate (single-grooved) pollen grains from the late Valanginian (~ 134 million years ago) found in Israel and Italy, initially at low abundance. Molecular clock estimates conflict with fossil estimates, suggesting the diversification of crown-group angiosperms during the Late Triassic or the Jurassic, but such estimates are difficult to reconcile with the heavily sampled pollen record and the distinctive tricolpate to tricolporoidate (triple grooved) pollen of eudicot angiosperms. Among the oldest records of Angiosperm macrofossils are Montsechia from the Barremian aged Las Hoyas beds of Spain and Archaefructus from the Barremian-Aptian boundary Yixian Formation in China. Tricolpate pollen distinctive of eudicots first appears in the Late Barremian, while the earliest remains of monocots are known from the Aptian. Flowering plants underwent a rapid radiation beginning during the middle Cretaceous, becoming the dominant group of land plants by the end of the period, coincident with the decline of previously dominant groups such as conifers. The oldest known fossils of grasses are from the Albian, with the family having diversified into modern groups by the end of the Cretaceous. The oldest large angiosperm trees are known from the Turonian (c. 90 Mya) of New Jersey, with the trunk having a preserved diameter of 1.8 metres (5.9 ft) and an estimated height of 50 metres (160 ft).

During the Cretaceous, ferns in the order Polypodiales, which make up 80% of living fern species, would also begin to diversify.
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