Back in 2018, along with a group of colleagues, I created a plot showing the age, size, and distribution of angiosperm woods from Cretaceous deposits around the world (Jud et al. 2018). This provides a sort of minimum estimate of tree size through time for the group. Not all specimens in the literature are included in the figure because not all of them have associated diameter estimates, but we included all the fossils that we could at the time and we expect to be biased in favor of large specimens. The data are available on GitHub.
The figure that appeared in the 2018 paper is somewhat busy highlighting a new discovery. Here is a simplified version of that plot that may be used with attribution. The blue points are from North America and the orange are from the rest of the world. What is not shown on this figure is all of the gymnosperm woods from the Cretaceous Period. Only a small percentage of these in the published literature include trunk diameter estimates, but we know that they occupied the full range of sizes possible in this plot. What I find remarkable is that for the first 30 million years or so (at least) of angiosperm evolution, large fossil woods (>10 cm in diameter) are very rare. This seems to reflect a real paleoecological pattern given how easy it is to find gymnosperm wood throughout the Cretaceous, and how easy it is to find angiosperm wood in uppermost Cretaceous and in Cenozoic deposits.
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