Overlap and contributions from source ontologies. A) Venn diagram showing the extent of cross-referenced content between msAOs prior to the merge. Note that there are no Xrefs between VSAO and TAO because TAO had obsoleted these classes and replaced them directly with VSAO classes prior to the merge with Uberon. B) Ontology evolution and integration into Uberon. The height of each bar corresponds to the number of classes, the arrows with dotted lines refer to when Xrefs to the source ontologies in Uberon were established. The thick black line refers to cloning (in the case of TAO and ZFA, where 2023 classes from ZFA were used to seed TAO), and the red line to replacement (TAO replaced classes with VSAO classes). Note that TAO, VSAO, AAO, and vHOG are no longer in development following the merge, and their content development will continue in the context of Uberon.