  In high-quality two-dimensional electrons confined to GaAs quantum wells,
near Landau level filling factors $\nu=$ 1/2 and 1/4, we observe signatures of
the commensurability of the electron-flux composite fermion cyclotron orbits
with a unidirectional periodic density modulation. Focusing on the data near
$\nu=1/2$, we directly and quantitatively probe the shape of the composite
fermions' cyclotron orbit, and therefore their Fermi contour, as a function of
magnetic field ($B_{||}$) applied parallel to the sample plane. The composite
fermion Fermi contour becomes severely distorted with increasing $B_{||}$ and
appears to be elliptical, in sharp contrast to the electron Fermi contour which
splits as the system becomes bilayer-like at high $B_{||}$. We present a
simple, qualitative model to interpret our findings.
