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

Resumen

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 Discoscaphites was 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.