Paleontologists analyze concretions—hard orbs of minerals that can collect around material like bone—and discover fossils of mammals that lived on Earth just after an asteroid killed the dinosaurs.
Mammal Fossils Fill in Missing Piece of the Timeline of Life
Published: October 24, 2019
Sharon Milito: When we first came out, we were just looking for whatever we could find. The important thing we wanted to find were mammal jaws and mammal teeth, but they were elusive. So, one day I was walking along in an area I’d been many times before, and I saw this white, round rock, sitting there on kind of its own little pedestal. And I picked it up and looked at it and as soon as I looked at it, I saw these teeth that were just smiling out at me. And I just almost had a heart attack.
Narrator: She’d found part of a mammal’s skull, one that could fit in the palm of her hand.
Milito: I was so excited because it was really, really well preserved.
Narrator: She brought the fossil to the Museum, where it was cataloged and filed away. It was years before Tyler happened across it.
Tyler Lyson: I was downstairs, just looking through the collection, pulling open drawers, and there sitting right in the front was the palate of a mammal. And I was absolutely astonished. I couldn’t believe it. And so, I was sort of thinking to myself, “There’s this complete of a skull here, there’s got to be more.”
Narrator: Sharon’s fossil had been found in a particular kind of rock called a concretion. Sometimes, concretions can form around organic material, like bone. And if conditions are right, they protect the fossil inside for eons.
Lyson: Sharon’s skull was incredibly lucky because it showed that yes, there are fossils inside and this is the type of rock to look for.
Narrator: Tyler decides to change his game and look for concretions to crack open. They hit the bluffs. Their eyes peeled for promising rocks. There’s a whole hillside of choices. One catches Tyler’s eye.
Lyson: I see this rock, this concretion on the ground. The very first one that I pick up and I crack it and it was amazing.
I just found a mammal skull.
Narrator: And that was just the beginning.
Ian Miller: It was crazy the way it happened. I mean, you could go your entire career as a mammal paleontologist and not find a skull from this time period. That’s how rare they are.
Lyson: We found I think 5 or 6 mammal skulls within about a 10-minute time span.
Miller: We were just laughing on the outcrop. Nothing like that’s ever happened to me before.
Lyson: I mean, amazing.
Narrator: They cracked the case and unearthed a trove of time capsules filled with clues.
Neil Shubin: So, what Tyler and Ian had discovered is a rosetta stone. And Corral Bluffs is telling us something very important. it’s telling us about ourselves—how we got to be here.
Rise of the Mammals
Executive Producer: Geoff Luck
Digital Producer: Ana Aceves
© WGBH Educational Foundation 2019