Late Cretaceous nodosaurids (Ankylosauria: Ornithischia) from México

nodosaurid ankylosaur remains from the upper cretaceous of mexico are summarized. the specimens are from the el gallo formation of baja california, the pen and aguja formations of northwestern coahuila, and the cerro del pueblo formation of southeast coahuila, mexico. these specimens show differences from other known nodosaurids, including an ulna with a well developed olecranon and prominent humeral notch, the distal end of the femur not flaring to the extent seen in other nodosaurids, and a horn-like spine with vascular grooves on one side. the specimens represent the southernmost occurrences of nodosaur remains in north america, and provide an important biogeographical link between nodosaurids of the united states and canada on the one hand, and argentina and antarctica on the other.