The number of Sox genes has remained stable since solitary and colonial ascidians separated.

Ciona sp. and Botryllus schlosseri genomes have a single C, D, E and F and two SOXB proteins.

Branchiostomafloridae genome encodes for 6 SoxB genes compared to an average of three in most chordate genomes.

Species-specific changes to SOX protein diversity is observed between the Florida and Chinese lancelet.

LCA of chordates had at least seven Sox genes, including the core suite of SoxB, C, D, E and F as well as SoxH.