  We study angular-dependent magnetoresistance in a low $T_c$ layered cuprate
Bi$_{2.15}$Sr$_{1.9}$CuO$_{6+\delta}$. The low $T_c$ ~ 4 K allows complete
suppression of superconductivity by modest magnetic fields and facilitate
accurate analysis of the upper critical field $H_{c2}$. We observe an universal
exponential decay of fluctuation conductivity in a broad range of temperatures
above $T_c$ and propose a new method for extraction of $H_{c2}(T)$ from the
scaling analysis of the fluctuation conductivity at $T>T_c$. Our main result is
observation of a surprisingly low $H_{c2}$ anisotropy ~ 2, which is much
smaller than the effective mass anisotropy of the material ~ 300. We show that
the anisotropy is decreasing with increasing field and saturates at a small
value when the field reaches the paramagnetic limit. We argue that the dramatic
discrepancy of high field and low field anisotropies is a clear evidence for
paramagnetically limited superconductivity.
