Data from: Partially incorrect fossil data augment analyses of discrete trait evolution in living species

Ancestral state reconstruction of discrete character traits is often vital when attempting to understand the origins and homology of traits in living species. Recently, the addition of fossils has been shown to alter our understanding of trait evolution in extant taxa, but researchers may avoid using fossils alongside extant species if only few are known, or if the designation of the character state is uncertain. Here, I investigate the impacts of fossils and incorrectly-coded fossils in the ancestral state reconstruction of discrete characters under a likelihood model. Under simulated phylogenies and data, likelihood-based models are generally accurate (~ 70% correct) when estimating ancestral node values. Fossils always out-perform data from extant species alone, and perform to a higher or similar standard even when up to half of fossils values are coded incorrectly. These results are especially pronounced when model assumptions are violated, such as when there is a trend away from the root value. Fossil data are of particular importance when attempting to estimate the root node value. Attempts should be made to include fossils in analysis of discrete traits under likelihood, even if there is uncertainty in the trait data.