  We follow the time evolution of a superfluid Fermi gas of resonantly
interacting $^6$Li atoms after a phase imprint. Via tomographic imaging, we
observe the formation of a planar dark soliton, its subsequent snaking, and its
decay into a vortex ring, which in turn breaks to finally leave behind a single
solitonic vortex. In intermediate stages we find evidence for an exotic
structure resembling the $\Phi$-soliton, a combination of a vortex ring and a
vortex line. Direct imaging of the nodal surface reveals its undulation
dynamics and its decay via the puncture of the initial soliton plane. The
observed evolution of the nodal surface represents dynamics beyond superfluid
hydrodynamics, calling for a microscopic description of unitary fermionic
superfluids out of equilibrium.
