Boletín de la Sociedad Geológica Mexicana Volumen 65, núm. 1, 2013, p. 189-200 http://dx.doi.org/10.18268/BSGM2013v65n1a14

Ammonoids from the Maastrichtian (Late Cretaceous) at El Zancudo, Nuevo Laredo, Tamaulipas, Mexico

Christina Ifrim^1,*, Wolfgang Stinnesbeck¹

¹ Geowissenschaftliches Institut, Universität Heidelberg, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany.

^* This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

A small assemblage of Maastrichtian ammonoids was collected at El Zancudo, south of Nuevo Laredo, Mexico, on the border with Texas. They are preserved as goethitic internal moulds of the innermost whorls. Nine taxa are described in abbreviated form. Eight taxa have been recorded from northeastern Mexico before: Baculites ovatus, Brahmaites (Anabrahmaites) vishnu (Forbes, 1846), Diplomoceras cylindraceum, Fresvillia sp. indet., Gaudryceras kayei, Hypophylloceras (Neophylloceras) cf. H. (N.) surya, Phyllopachyceras forbesianum, and Tetragonites superstes. The genus Discoscaphiteswas recorded and described for the first time in this region. The assemblage indicates an early late Maastrichtian age and is compared to other ammonoid assemblages from Texas and northeastern Mexico. It provides an important level marker for long-distance correlation into the deltaic sediments of northeastern Mexico, known as the Difunta Group.

Keywords: ammonoids, biostratigraphy, Cretaceous, Maastrichtian, Mexico, paleobiogeography, systematic description.