  By utilizing the gauge symmetries of Two-Time Physics (2T-physics), a
superstring with linearly realized global SU(2,2|4) supersymmetry in 4+2
dimensions (plus internal degrees of freedom) is constructed. It is shown that
the dynamics of the Witten-Berkovits twistor superstring in 3+1 dimensions
emerges as one of the many one time (1T) holographic pictures of the 4+2
dimensional string obtained via gauge fixing of the 2T gauge symmetries. In
2T-physics the twistor language can be transformed to usual spacetime language
and vice-versa, off shell, as different gauge fixings of the same 2T string
theory. Further holographic string pictures in 3+1 dimensions that are dual
theories can also be derived. The 2T superstring is further generalized in the
SU(4)=SO(6) sector of SU(2,2|4) by the addition of six bosonic dimensions, for
a total of 10+2 dimensions. Excitations of the extra bosons produce a SU(2,2|4)
current algebra spectrum that matches the classification of the high spin
currents of N=4, d=4 super Yang Mills theory which are conserved in the weak
coupling limit. This spectrum is interpreted as the extension of the SU(2,2|4
classification of the Kaluza-Klein towers of typeII-B supergravity compactified
on AdS{5}xS(5), into the full string theory, and is speculated to have a
covariant 10+2 origin in F-theory or S-theory. Further generalizations of the
superstring theory to 3+2, 5+2 and 6+2 dimensions, based on the supergroups
OSp(8|4), F(4), OSp(8*|4) respectively, and other cases, are also discussed.
The OSp(8|4) case in 6+2 dimensions can be gauge fixed to 5+1 dimensions to
provide a formulation of the special superconformal theory in six dimensions
either in terms of ordinary spacetime or in terms of twistors.
