Atypical angucyclines are a class of aromatic polyketides with unique structures and formed via oxidative rearrangement reactions. Recent studies have demonstrated that their various skeletons are derived from a common biosynthetic intermediate dehydrorabelomycin. A unique family of oxygenases, atypical angucycline ring-opening oxygenases, catalyzes the oxidative carbon-carbon bond cleavage and rearrangement reactions of dehydrorabelomycin, which is a critical step in the biosynthesis of these compounds. Although these ring-opening oxygenases belong to the same protein family, and catalyze the oxidative ring-opening reaction of the same substrate dehydrorabelomycin, different rearrangement reactions render different structures of the products, which are consistent with the skeletons of their final products. The in-depth study on the catalysis of this family of oxygenases will not only contribute to the structural modification of known aromatic polyketides and the discovery of polyketides with novel skeletons, but also help to deepen our understanding of protein sequence evolution and functional diversities.