Systematic features of anomalous signature splitting of the πh11/2 vi13/2 band in A ～ 160 odd-odd nuclei have been investigated. It is shown that the mechanism of anomalous signature splitting is similar to that of the normal signature splitting which is essentially caused by the Coriolis mixing of Ω = 1/2 components into the nuclear wavefunction and the anomalous splitting in signature is mainly caused by the definition. The extensively observed anomalous signature splitting in this band might be an indication that the interaction between the h11/2 proton and the i13/2 neutron cannot be neglected. The new observation of high- and low-K bands based on the same πh11/2 vi13/2 configuration in 164Tm is also discussed.