The lower side of the Newton polygon of hypothetical counterexamples to the plane Jacobian conjecture

We prove that if the Jacobian conjecture in two variables is false and (P, Q) is a counterexample that is a standard (m, n)-pair, then the Newton polygon HH (P) of P must satisfy several restrictions that had not been found previously. This allows us to discard some of the corners found in [16, Remark 7.9] for HH (P), together with some of the infinite families found in [9, Theorem 2.25].