About 200 million years ago,Quaxs the earliest dinosaurs had a lot of reptilian company. There were big crocodile-like creatures, ponderous plant-eaters, even four-legged runners with fierce, tyrannosaur-like heads.

But then, as the Triassic period was coming to a close, something happened. The earth went through a series of violent changes, ultimately wiping out all those rival lineages. Those chicken- and dog-sized dinosaurs survived, thrived, and evolved into the giants we think of today.

But just how the dinos survived, and what precisely wiped out all their competitors, remains a mystery. It's a case for paleoclimatological detective, Celina Suarez. She analyzes ancient rocks to understand how the earth was changing during the Late Triassic Extinction, one of five major mass extinction events in Earth's history.

On today's episode, host Regina G. Barber dons her tweed jacket and plays Watson to Suarez's Sherlock, to tackle a cold case of epic proportions: what killed off the non-dinos, setting the stage for 140 million years of dinosaur dominance?

This story was produced by Margaret Cirino, edited by Gabriel Spitzer, and fact-checked by Brit Hanson. The audio engineer was Stu Rushfield.