Eons

The remains of medium-sized predatory dinosaurs are pretty rare in places where giant predators like T. rex existed. Which is weird, because that’s just not how ecosystems work today.

The Wrangel Island mammoths would end up being the final survivors of a once widespread genus. In their final years, after having thrived in many parts of the world for millions of years, the very last mammoths that ever lived experienced what’s known as a mutational meltdown.

Lots of the traits we think of as defining us as mammals show up pretty early, during the time of the dinosaurs. And, in some cases, they show up a lot earlier and in things that weren’t mammals at all.

At Tanque Loma, at least 22 giant ground sloths in the genus Eremotherium met their end. Of the five hypotheses that researchers proposed for what killed the sloths, the best supported one right now is that they died surrounded by their own poop.