#alamosaurus

This would all be happening west of Hell Creek in the foothills of what will one day be the Rockies, but aside from Alamosaurus and possibly Arambourgiana (especially since as far as I know the North American material is only tentatively assigned to the genus), all these animals were present in Hell Creek as well.

Keychain charm of the North American titanosaur Alamosaurus. Used a celadon glaze over clay inlay.

The Browsing Alamosaurus from Dinosaur!(1985) and Phil Tippett Studios.

(RECOMMENDED LISTENING)

"It's the biggest lifeform ever encountered. Anywhere."

Alamosaurus is one of the largest known sauropods, and the largest known sauropod in Laramidia, at least during the Maastrichtian.

(Image by Mark Witton.)

They are big enough to tell an adult T. rex to go fuck itself and get away with it.

...And unfortunately they are not found in Hell Creek, preferring dryer lands to the south.