By Michael F. Duggan
Thescelosaurus neglectus—mark the name well. It is a notable discovery in the history of paleobiology. The species itself is not especially noteworthy, novel, or newly discovered; Thescelosauruses were a common, small, bipedal dinosaur of the late Cretaceous period. It is a particular fossil that is important.
Scientists at the Tanis dig site in the Badlands of North Dakota might have found the mineralized remains of an individual animal that was killed on the exact day that a 12-kilometer wide asteroid punched a 180-kilometer-wide hole in what is now the Yucatan Peninsula (the Chicxulub Crater) almost 66 million years ago. Debris found with the fossil indicate that it is a snapshot of the instant that the Cretaceous Period became the Paleocene (and, more grandly, when the Mesozoic Era became the Cenozoic). It is the moment that the reign of the dinosaurs ended.
Tanis has been famous as a dig site for more than a decade because its fossils date from the precise time of the Cretaceous die-off.
Depending on how you measure them, over the past 540 million years, mass die-offs have occurred about about every 27 or 28 million years. Since the Cambrian Explosion that created the diverging categories of the phyla of biology, there have been at least five cataclysmic die-offs (the ones that ended the Ordovician, Devonian, Permian, Triassic, and yes, the Cretaceous period). Our own period appears to be the sixth mass extinction of the Earth’s living history.
Sometimes I feel a little like the animal represented by this fossil: after about 7,500-15,000 human generations, I happen to live in the time when the existing world is falling apart (although, to be fair, dinosaurs were around for about 180 million years where modern humans have only been here for about 300,000 years—and perhaps as little as 150,000-200,000 years—or around one 600th of their tenure at most).
I guess the difference is that humans are both the asteroid and its victim.