Fossil Angiosperms and Leaf Architecture

Fossil flowering plants record the Cretaceous rise of angiosperms, and the architecture of their fossil leaves provides quantitative proxies for past climate.

Definition

Fossil angiosperms are the preserved remains of flowering plants; leaf architecture is the study of fossil leaf form, venation, and margins, used both to identify plants and to reconstruct paleoclimate.

Scope

This topic covers the origin and explosive Cretaceous radiation of flowering plants, fossil flowers, pollen, fruits, and wood, and the analysis of fossil leaf shape and margins to estimate past temperature and precipitation.

Core questions

• When and how did flowering plants originate and radiate?
• What do the earliest fossil flowers reveal about angiosperm evolution?
• How is fossil leaf margin analysis used to estimate past climate?
• How did angiosperms transform terrestrial ecosystems?

Key concepts

• Angiosperm origin and radiation
• Fossil flowers and pollen
• Leaf margin analysis
• Leaf physiognomy climate proxies

Key theories

Cretaceous angiosperm radiation

Fossil flowers, pollen, and leaves document the rapid mid-Cretaceous rise and ecological takeover of flowering plants, an event Darwin called an abominable mystery.

Leaf physiognomy as a climate proxy

The proportion of fossil dicot leaves with smooth versus toothed margins and other leaf traits correlate with temperature and precipitation, enabling paleoclimate estimates.

Clinical relevance

Fossil angiosperms document the assembly of modern terrestrial ecosystems, and quantitative analysis of fossil leaf architecture provides widely used proxies for reconstructing past temperature and rainfall.

History

Charles Darwin highlighted the sudden appearance of flowering plants as an abominable mystery. Discoveries of tiny well-preserved Cretaceous flowers and the development of leaf-physiognomy methods in the twentieth century advanced both angiosperm phylogeny and paleoclimate reconstruction.

Debates

Timing and cause of angiosperm origins

The age of the first flowering plants and the drivers of their rapid radiation are debated between fossils and molecular clocks.

Key figures

• Else Marie Friis
• Peter R. Crane
• Jack A. Wolfe

Seminal works

• friis2011
• taylor2009

Frequently asked questions

When did flowering plants appear?

Flowering plants appear in the fossil record in the Early Cretaceous and radiated rapidly to dominate many ecosystems by the Late Cretaceous.

How do leaves tell us about ancient climate?

The shape and margins of fossil leaves correlate with temperature and rainfall, so leaf assemblages can be used to estimate past climate.