Mosasaur vertebra embedded in shelly sandstone with dark ejecta spherules from Chicxulub (See more images with dinosaur tooth)

New finds of a dinosaur tooth (here) (?Ornithomimus), and a Mosasaur vertebra (here) within tsunami deposits with ejecta of the Chicxulub impact in the La Popa (near Monterrey, Mexico) basin demonstrate that these reptiles lived up to the K/T boundary, and have not disappeared before the Chicxulub impact.
The tooth and vertebra were lying around on the surface further west in the Parras basin where more dinosaur remains have been found, and were washed in the sea by the tsunami backwash.
Regarding their good preservation, the fossils were likely not buried in the ground, before being back-washed with the tsunami bores


La Popa K/T boundary

The Popa Basin on Google Earth
The outcrop of the tsunamites where the vertebrate remains were found