An ancient whole-genome duplication in barnacles contributes to their diversification and intertidal sessile life adaptation

•We sequenced and assembled a chromosome-level barnacle genome.•A WGD event was identified in barnacles for the first time.•This WGD event is more ancient than the divergence of Thoracicalcarea.•Ohnologs were subject to sub- or neo-functionalization for intertidal adaptation.•The ancient WGD event may associate with the origin and diversification of thoracican barnacles.