Novel MgO fishbone- or fern-like nanostructures, and Al2O3 fibre networks, have been generated for the first time from an Al2O3 matrix containing MgO and SiO2. The significance of the selective Co-catalysed growth of the elegant three-dimensional fractal fishbones is discussed. We have adopted the vapour-liquid-solid (V-L-S) and nucleation-aggregation (N-A) mechanisms, which take effect equally during the heating process, to account for the formation of these uniquely stacked fractal structures.