Morphological diversity and complexity are notable features of multicellular life, although whether they evolve gradually or in early bursts is unclear. Vascular plant reproductive structures, such as flowers, are familiar examples of complicated morphology, and here we analyze changes in complexity over time using a simple approach based on the number of part types. We find that reproductive complexity increased in two pulses separated by nearly 250 million years of stasis, including an initial Devonian rise with the radiation of vascular plants and a dramatic Late Cretaceous increase reflecting flowering plant diversification. These pulses are associated with innovations that increased functional diversity, suggesting that shifts in complexity are linked to changes in function, regardless of whether they occur early or late in the history of vascular plants.

Morphological data was collected from published literature sources and direct observations of plant reproductive structures.

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