  Different phases in open driven systems are governed by either shocks or
rarefaction waves. A presence of an isolated umbilic point in bidirectional
systems of interacting particles stabilizes an unusual large scale excitation,
an umbilic shock (U-shock). We show that in open systems the U-shock governs a
large portion of phase space, and drives a new discontinuous transition between
the two rarefaction-controlled phases. This is in contrast with strictly
hyperbolic case where such a transition is always continuous. Also, we describe
another robust phase which takes place of the phase governed by the U-shock, if
the umbilic point is not isolated.
