  The breakup of shearless invariant tori with winding number
$\omega=[0,1,11,1,1,...]$ (in continued fraction representation) of the
standard nontwist map is studied numerically using Greene's residue criterion.
Tori of this winding number can assume the shape of meanders (folded-over
invariant tori which are not graphs over the x-axis in $(x,y)$ phase space),
whose breakup is the first point of focus here. Secondly, multiple shearless
orbits of this winding number can exist, leading to a new type of breakup
scenario. Results are discussed within the framework of the renormalization
group for area-preserving maps. Regularity of the critical tori is also
investigated.

Chaotic Dynamics