  We present multi-epoch Spitzer Space Telescope observations of the
transitional disk LRLL 31 in the 2-3 Myr-old star forming region IC 348. Our
measurements show remarkable mid-infrared variability on timescales as short as
one week. The infrared continuum emission exhibits systematic
wavelength-dependent changes that suggest corresponding dynamical changes in
the inner disk structure and variable shadowing of outer disk material. We
propose several possible sources for the structural changes, including a
variable accretion rate or a stellar or planetary companion embedded in the
disk. Our results indicate that variability studies in the infrared can provide
important new constraints on protoplanetary disk behavior.
