Two new bismuth compounds, oxovanadate Bi-3(VO4)O-3 and oxoarsenate Bi-3.5(AsO4)(OH)(0.5)O-3.5, were prepared using supercritical hydrothermal pressure. Dealing with the anionic sublattice, both crystal structures are built on anti-oxo-OBi4/OBi3 or -OBi4/OBis units connected together in infinite corrugated 2D layers surrounded by isolated XO4 (X = V or As) tetrahedra. These edifices complete a series initiated by the recent Bi-3(PO4)O-3 prepared under similar conditions. With the latter being assigned to the "simplest" bioxophosphate in terms of structural complexity, this aspect was investigated among the other compounds in their chemical ternaries. These phases are suggested to be high-pressure polymorphs, not possible to tackle when working at ambient pressure and temperature conditions.