  We propose new textures for the fermion Yukawa matrices which are
generalizations of the so-called Stech ansatz. We discuss how these textures
can be realized in supersymmetric grand unified models with horizontal symmetry
SU(3)_H among the fermion generations. In this framework the mass and mixing
hierarchy of fermions (including neutrinos) can emerge in a natural way. We
emphasize the central role played by the SU(3)_H adjoint Higgs field which
reduces SU(3)_H to U(2)_H at the GUT scale. A complete SO(10)\times SU(3)_H
model is presented in which the desired Yukawa textures can be obtained by
symmetry reasons. The phenomenological implications of these textures are
thoroughly investigated. Among various realistic possibilities for the Clebsch
factors between the quark and lepton entries, we find three different solutions
which provide excellent fits of the quark masses and CKM mixing angles.
Interestingly, all these solutions predict the correct amount of CP violation
via the CKM mechanism, and, in addition, lead to an appealing pattern of the
neutrino masses and mixing angles. In particular, they all predict nearly
maximal 23 mixing and small 12 mixing in the lepton sector, respectively in the
range needed for the explanation of the atmospheric and solar neutrino anomaly.
