Phenotypic disparity and species diversity are the hallmarks of biodiversity. Morphological traits that promote the invasion of, and diversification within, new adaptive zones are expected to be more common across the tree of life. Historically, such traits were defined as ‘key innovations’ since they could explain the evolutionary success of a taxonomic group. Morphologists have embraced the concept of key innovations, and have used it extensively to explain many cases of adaptive radiations.