Cartesian Morphism of Polynomial Functors

A cartesian morphism of polynomial functors is a Cartesian Morphism in the Category of Polynomial Functors. More explicitly, it is a morphism of polynomial functors $(f,f^{\sharp}):P\to Q$ such that $f^{\sharp}$ is an equivalence.

This can easily be seen by studying the Cartesian Morphisms of the Family Fibration, recalling that $\mathrm{Poly}=\mathrm{Fam}(\mathrm{Sets}^{\mathrm{op}})$.