Blanco-Piñón A, Garibay-Romero LM. The oldest stratigraphic record of the Late Cretaceous shark Ptychodus mortoni Agassiz, from Vallecillo, Nuevo León, northeastern Mexico. revmexcg [Internet]. 2018 Jan. 16 [cited 2025 May 10];25(2):367-8. Available from: https://rmcg.unam.mx/index.php/rmcg/article/view/666