THE BRAIN SCOOP - FOSSIL FISH PART II: A HISTORY

Lance Grande: So see, he plowed up this giant rock here and it's got a palm leaf on it.

Emily Graslie: Oh Wow!

A BRAIN SCOOP FIELD TRIP TO FOSSIL LAKE (DAY 2): A BRIEF HISTORY OF FOSSIL LAKE

Emily: So we're here with Lance Grande, who is the Distinguished Service Curator at the Field Museum, and we are standing in a giant rock quarry in Wyoming.

Lance: This great lake system, called the Green River Lake System, which persisted almost twenty million years...

Emily: Oh man,

Lance: ...one of the longest-lived lake systems that we know of.

Emily: Wow

Lance: And we're in the smallest and shortest-lived of those lakes, fossil lakes, which probably only existed a million and a half years...

Emily: Gosh

Lance: ...but that's a long time for any lake, especially when you consider the Great Lakes of North America are only about ten thousand years old

Emily: Wow, yeah, we got nothing on this lake system!

Lance: We have an entire community here that's logged in stone. We're out here lifting these slabs and we're seeing all kinds of things that haven't seen the light of day for fifty-two million years.

(fig. A) ON NOT LOOKING FOR DINOSAURS (01:14)

Emily: I think most people, when you tell them that you're going on a paleo dig, they assume you're looking for dinosaurs... and clearly we're not finding any dinosaurs, of the typical kind out here, but we are finding an entire ecosystem, essentially.

Lance: Well, it's interesting you bring up dinosaurs because one of the interesting things about this site is... you know about sixty-five million years ago we had the extinction of most of what we think of as dinosaurs except for the bird lineage. That was due to a meteorite impact off the coast of Yucatan, which left a fifty mile wide crater there. 

It extinguished more than fifty percent of all the species on the planet, and what we're seeing here is how the Earth is recovering after that.

Emily: This is the largest or most complete representation of early Eocene life in the world...

Lance: By far. This is an amazing locality... this is probably the most productive fossil locality in North America.

Emily: Really?

Lance: We have a lot of different birds coming in, in a sky that's no longer ruled with Pterosaurs.

Emily: Right...

Lance: We've got mammals taking the place of all these terrestrial dinosaurs that existed before. And although they are very peculiar when you compare them to mammals and some birds today, they are nevertheless representatives of these modern families.

(fig. B) CLIMATE AND GEOLOGICAL TIME (02:38)

Emily: It is very hot, I've noticed this! It didn't take me very long to realize there's not a lot of shade around here... and it's curious to me because we are standing next to what is obviously and evidently evidence of a palm frond, which indicates that this climate is much different today than it was millions of years ago.

Lance: This high mountain desert is a real contrast to the subtropical environment that existed here fifty-two million years ago. We not only have these palms that the bulldozer pried up yesterday, there was a crocodile found right over there which was bout twelve feet long... and you have chunks like this which represent volcanic ash. There were active volcanoes around the lake.

Remember we are talking about geologic time, so when we look at this quarry here and go all the way up to the top of the highest quarry here, we may be talking about fifty-thousand years or more. And if you think in ecological time, how much can happen in even a hundred years or a thousand years, the fact that we find volcanic eruptions and maybe signs of earthquakes, that is just common and it's compressed time because we are looking at geologic time.

(fig. C) WHAT WAS AT FOSSIL LAKE? (03:54)

Emily: So, in addition to finding random fishes you will find like little schools of mini fishes and that sort of thing, but we're also finding and discovering behaviors of animals that were previously unknown.

Lance: This site is so amazing, and there was this flash preservation of things, almost, and so I can come out and I can find fishes that are in the process of choking to death on other fishes, fishes with stomach contents - other animals that they've swallowed. I can find leaves with insect chew marks and the insects that made the chew marks.

There is even a stingray, a rare stingray here called Asterotrygon. We have a mated pair that are actually clasped together (04:38), and then a pregnant female, and then another slab with a female that had just given birth with two young beside it.

Emily: A lot of the stuff that we are finding here too, yes they're extinct, but they are not totally unknown or unrecognizable species.

Lance: Just the other day there were two six-foot turtles found in the quarry next to us.

Emily: Really?!

Lance: There's a three-toed horse comes out of this quarry, it's about twenty-four inches high at the shoulder as an adult. This place has been mined for fossils for more than one hundred and fifty years, and there have probably been three million fishes excavated in that time, and there is still a fish that's only known by one specimen - a pike. In three million fishes, only one a pike, and what that tells me is there's so many things here that we haven't found yet, it's just, you need almost an infinite sample size to know what actually existed then.

Emily: We have a very pieced together map of life on Earth as we know it and, by looking at places like this sort of locality, we are able to find the puzzle pieces that fit into the time-line, essentially.

Lance: Well that's exactly right. The evolutionary pattern is a network and we find pieces of it in almost every group. We have the bird that is the missing link between the swifts and the hummingbirds. We have fishes that link different families. We have all kinds of things here that literally answer questions about evolutionary trees that we were previously unable to put together.

Emily: Do you think we will ever exhaust this area? Do you think we will ever get to a point where people think we have found everything that there is to find here?

Lance: No... (laugh)... it would be impossible.