The claim is the Tanis creatures were killed and entombed on the actual day a giant asteroid struck Earth.
The impact site has been identified in the Gulf of Mexico, off the Yucatan Peninsula. That's some 3,000km away from Tanis, but such was the energy imparted in the event, its devastation was felt far and wide.
The North Dakota fossil site is a chaotic jumble.
The day 66 million years ago
Regrettably, their Zoomers were completely destroyed, so no exact date available.
when the reign of the dinosaurs ended and the rise of mammals began.
The remains of animals and plants seem to have been rolled together into a sediment dump by waves of river water set in train by unimaginable earth tremors. Aquatic organisms are mixed in with the land-based creatures.
The sturgeon and paddlefish in this fossil tangle are key. They have small particles stuck in their gills. These are the spherules of molten rock kicked out from the impact that then fell back across the planet. The fish would have breathed in the particles as they entered the river.
The spherules have been linked chemically and by radiometric dating to the Mexican impact location, and in two of the particles recovered from preserved tree resin there are also tiny inclusions that imply an extra-terrestrial origin...