These are IFSs in which the elements are laid out in the form of a cross, and the overall attractor approaches a cross as the number of elements approach infinity. The first order cross fractal or cruciopentamer is the cyclotetramermonomer or Mandelbrot quintet. The remainder are generated by replacing each component of this by n2 elements. The angle by which the elements are rotated with respect to the whole figure remains arctan(0.5) for all members of the series. For each n there are cis- and trans- variants.
Source: The cis-cruciopentamer (aka cis-cyclotetramermonomer aka cross fractal aka Mandelbrot quintetwas reverse-engineered from an image and recursive construction found on the web. The trans-cruciopentamer immediately follows by application of the trans technique. Discovering two s-pentaicosamers that each could be combined in pairs to form the cis- and trans-cruciopentamers, and additional s-polymers with greater numbers of elements that also could be combined in pairs to form tiles with c4symmetry lead to an intuition that the higher order cross fractals were possible, whereupon they were readily found. Note however that these don't correspond to the additional tiles formed to c2-symmetric s-polymers, so there may be additional fractals to be discovered.