A sign-reversing involution for an extension of Torelli's Pfaffian identity

We evaluate the hyperpfaffian of a skew-symmetric k-ary polynomial f of degree k/2⋅(n−1). The result is a product of the Vandermonde product and a certain expression involving the coefficients of the polynomial f. The proof utilizes a sign reversing involution on a set of weighted, oriented partitions. When restricting to the classical case when k=2 and the polynomial is (xj−xi)n−1, we obtain an identity due to Torelli.