Our knowledge of morphology is largely implicit and not normally accessible to comparative analysis tools. Much of this knowledge is, however, encoded in ontologies.The Semantic Comparative Analysis for Trait Evolution project (scate.phenoscape.org) is developing tools that use the computable knowledge in ontologies to improve models of trait evolution. These new tools provide access to and take advantage of the semantics of phenotypes available from the Phenoscape Knowledgebase.