Fire biases the production of charred flowers: Implications for the Cretaceous fossil record

Abstract

The radiation of angiosperm lineages during the Cretaceous Period (145.5–65.5 Ma) initiated one of the greatest floral turnovers to have occurred on our planet. Much of our understanding of the floral biology and diversity of these early angiosperms derives from exceptionally preserved charcoalified and coalified Cretaceous fossil floras. Although fire played an integral role in the production of charred early angiosperm flowers, research has not considered whether the fire is capable of creating a bias in the nature of the charcoalified flowers that are produced. Here we use calorimetry to experimentally produce morphologically variable charcoalified flowers. Our findings indicate that combustion behavior, floral structure, the number of flowers, and their arrangement (inflorescence) all affect the number of charred flowers that are produced. These observations suggest that charred flowers are not equally likely to be represented in Cretaceous charcoal assemblages, and some species may be missing from the fossil record entirely. This may in turn alter our understanding of early angiosperm evolution and the fossil record of fire.