Blanco-Piñón, Alberto, and Luis M. Garibay-Romero. “The Oldest Stratigraphic Record of the Late Cretaceous Shark Ptychodus Mortoni Agassiz, from Vallecillo, Nuevo León, Northeastern Mexico”. Revista Mexicana de Ciencias Geológicas 25, no. 2 (January 16, 2018): 367–368. Accessed May 10, 2025. https://rmcg.unam.mx/index.php/rmcg/article/view/666.