  We analyze several unusual filamentary structures, which appeared in the
umbra of one of the sunspots in AR 11302. They do not resemble typical light
bridges, neither in morphology, nor in evolution. We analyze data from SDO/HMI
to investigate their temporal evolution, Hinode/SP for photospheric inversions,
IBIS for chromospheric imaging, and SDO/AIA for the overlying corona.
Photospheric inversions reveal a horizontal, inverse Evershed flow along these
structures, which we call umbral filaments. Chromospheric images show
brightenings and energy dissipation, while coronal images indicate that bright
coronal loops seem to end in these umbral filaments. These rapidly evolving
features do not seem to be common, and are possibly related to the high
flare-productivity of the active region. Their analysis could help to
understand the complex evolution of active regions.
