We examine the dynamics of low plasma beta (¿ = 0.05), high Alfv¿n Mach number (M A = 4 ~ 5), quasi-perpendicular ($theta$ bn = 87¿) collisionless shocks using two one-dimensional hybrid simulation codes, a standard hybrid code with massless fluid electrons and a new extended hybrid code with finite electron mass, and the full electron pressure tensor. Both hybrid codes predict similar macroscopic shock structures with well defined foot, ramp, overshoot and downstream regions and a shock that reforms with a quasi-cyclic change of the shock front structure. The shock reformation period predicted by the standard hybrid code is 1.8Ω ci -1 (Ω ci is the upstream ion gyrofrequency). In contrast to the standard hybrid simulations, the additional electron dissipation in the new extended hybrid code leads to a strong ion thermalization and phase space mixing between upstream incoming and reflected ions via plasma wave interactions in the foot, and formation of ion phase space holes. Whistler waves with typical wavelength $simeq$0.3v A Ω ci -1 and frequency $simeq$5.5Ω ci -1 are observed in the foot, and ramp region which help to stop the shock steepening, and reduce the predicted shock reformation period to 1.6Ω ci -1.