  We show that $\Gamma$-free fillings and lonesum fillings of Ferrers shapes
are equinumerous by applying a previously defined bijection on matrices for
this more general case and by constructing a new bijection between Callan
sequences and Dumont-like permutations. As an application, we give a new
combinatorial interpretation of Genocchi numbers in terms of Callan sequences.
Further, we recover some of Hetyei's results on alternating acyclic
tournaments. Finally, we present an interesting result in the case of certain
other special shapes.
