We define the ``infinitesimal Brunovsky form'' for nonlinear systems in the infinite-dimensionnal differential geometric framework devellopped in ``A Differential Geometric Setting for Dynamic Equivalence and Dynamic Linearization'' (Rapport INRIA No XXXX, needed to understand the present note), and link it with endogenous dynamic linearizability, i.e. conjugation of the system to a linear one by a (infinite dimensional) diffeomorphism.