We study a system of uniaxial hard ellipsoids by molecular dynamics simulations, changing both the aspect-ratio X0 (X0 = a/b, where a is the length of the revolution axis and b is the length of the two other axes) and the packing fraction ø. We calculate the translational 〈r2(t)〉 and rotational 〈Φ2(t)〉 mean squared displacements, the translational Dtrans and the rotational Drot diffusion coefficients and the associated isodiffusivity lines in the ø- X0 plane. For the first time, we characterize the cage effect through the logarithmic time derivative of logr2(t) and log2(t). These quantities exhibit a minimum if the system is supercooled and we show that, consistently with our previous findings, for large and small X0 values, rotations are supercooled, contrary to translations. In agreement with this scenario, while the self-intermediate scattering function exhibits stretched relaxation (i.e. glassy dynamics) only for large and X0 1, the second order orientational correlator C2(t) show stretching only for large and small X0 values. As further evidence of this pre-nematic order driven glass transition, we observe a decoupling of the translational and rotational dynamics, which generates an almost perpendicular crossing of the Dtrans and Drot isodiffusivity lines. © 2008 Taylor & Francis.