We present a measurement of the t(t) over bar differential cross section with respect to the t(t) over bar invariant mass, d sigma/dM(t(t) over bar), in p(p) over bar collisions at root s=1.96 TeV using an integrated luminosity of 2.7 fb(-1) collected by the CDF II experiment. The t(t) over bar invariant mass spectrum is sensitive to a variety of exotic particles decaying into t(t) over bar pairs. The result is consistent with the standard model expectation, as modeled by PYTHIA with CTEQ5L parton distribution functions.