Babies Everywhere

We spent six full seasons at the Willow Creek anticline, from 1979 through 1984. Then the Peebles family decided they wanted to trade in the land on which we'd found the fossils. Because the site was something Montana was proud of, particularly since the fossils and reconstructions were staying in Bozeman, the Peebles hoped to give the state the fossil-ridden badlands in return for a larger amount of good pasture land. I don't quite know the reasoning behind the desire for the swap, except that I suppose with 20 or so crew members on the site each summer and a few hundred visitors, the Peebles must have felt that this small chunk of land had already become somewhat public.

The state of Montana and the Peebles family couldn't come to terms, and this meant the Peebles did not invite us back for the 1985 season. In 1987, the Nature Conservancy bought the land in question. Now, if we want to, we can go back, and we may; however, since we left the anticline, we've found other sites that demand our attention.

In looking back at the dig at the Willow Creek anticline, I'm struck by several things. One is that the dig changed my professional life. I went from preparator to curator. I started getting significant grants. I became able to muster the funding and institutional support to conduct the kind of work I wanted to do. The dig also took charge of the direction of my work. What I mean is that from the finds at the dig, new questions and problems emerged for me to follow. By the time we finished at the anticline, we knew we had hold of a good piece of string that would pull us much deeper into the tangle of dinosaurs. We really had no choice but to keep pulling.

You can summarize the finds at the Willow Creek anticline in terms of quantity, of firsts. In two square miles, we uncovered the first clutches of dinosaur eggs in North America and the first nests of baby dinosaurs anywhere. We found the first evidence of colonial nesting for two quite different species of dinosaurs. We uncovered the first evidence of parental care in dinosaurs—evidence that made Maiasaura's behavior more reminiscent of birds than of reptiles. We found the remnants of the largest herd of dinosaurs yet known. And we discovered two new species of dinosaurs: Maiasaura peeblesorum and Orodromeus makelai.

This is, however, a very superficial way of looking at the dig and at paleontology. It's more like compiling baseball statistics. What's important is to look at what the finds meant, what they told us about dinosaurs that we hadn't known before, and what they suggested we might be able to find out about dinosaurs if we just kept looking a bit longer.

Certainly, the most important finds were the nesting grounds— the eggs, the embryos, the babies. They were important because we learned things we hadn't known before and we were able to guess at others. We learned without any doubt that at least two species of dinosaurs gathered in colonial nesting grounds, collecting in birdlike flocks to lay their eggs. We learned that both the maiasaurs and the hypsilophodontids grew rapidly, like birds, and that the maiasaur adults seem to have cared for their young by bringing them food in the nest. There are critics who say that we can't be sure of this behavior, that the evidence just isn't sufficient, but I've explained why I can't see any other explanation for what we found. And I think these discoveries alone caused a significant shift in our attitude about dinosaurs, not so much about what they looked like, or even about their physiology (although it seems clear to me that these fossils and the studies we've done of them support the idea of endothermy in dinosaurs), but about the kind of creatures they were, about how they behaved.

To envision dinosaurs gathered in aggregations to lay eggs, to see them bringing food to their young, is to imagine them in a new way, to begin to see that dinosaurs were something different. I don't mean to say that the Willow Creek anticline fossils alone are causing this change. But they provide some rigid, documentary skeletons for theory and speculation. Having considered what we found at the anticline, I think it's undeniable that the dinosaurs weren't just big lizards. They weren't mammals or birds, either, and I don't want to anthropomorphize them when I talk about babies; their child care was not the same as the care that goes on in our own species. They were dinosaurs, different from all living creatures in many ways, some of which we know about and some of which we'll probably never know about. The picture we have of dinosaurs will always have its blank spots, places where we have to guess to fill in an image, the way we sometimes guess when we reconstruct skeletons.

The fossils from the Willow Creek anticline also reinforced the notion that some dinosaurs lived in herds. This was an idea for which there was already fossil evidence, and the big bone bed we found provided a new and compelling reason to think of some dinosaurs as herd animals. The maiasaurs lived in aggregations of 10,000 individuals or more. And finding the herd led me to speculate that perhaps the dinosaurs exhibited some of the behavioral characteristics of modern herbivorous mammals beyond simple herding. As big herbivores in social groups, they may have been solving similar evolutionary problems. As I said earlier (and as others have said before me) I think the horns and frills, and crests, and vertical plates we see on various dinosaurs did not evolve as means of defense any more than the horns of bighorn sheep evolved as means of defense. My opinion is that they were sexual signals, a means for the males to advertise themselves and compete for females.

Finally, the physical nature of Maiasaura, her evolutionary conservatism, and her geographical location in the mountains gave me some very specific ideas about how dinosaurs, particularly the hadro-saurs and lambeosaurs, evolved during the Cretaceous period in North America. To summarize again what I described in Chapter 3, I felt that the movements of the inland sea were driving evolutionary change, compressing habitat and then opening it up wide, in each case causing a burst of evolution and the appearance of many new species. I expected to see the most rapid evolutionary change around the peak of each transgression, when the sea extended its farthest. I thought sediments from those times would provide a lot of new species.

To me the Willow Creek anticline was as much a fountain of ideas as it was a trove of fossils. And in science what you do with ideas, with guesses or hypotheses or tentative conclusions, is to try to confirm or disprove them. Even though paleontology is a historical science, testable predictions are still possible. A paleontologist might say: "Well, look, I know where to find baby dinosaur bones. I've found enough that I figure I've got this puzzle solved. You give me the geologic maps, and I can pick out the spots where you'll find nests, eggs and babies, from the Triassic, the Jurassic, the Cretaceous, from Asia, Europe, South America, North America—anywhere, any geologic time, I can tell you where the baby dinosaurs are." If anyone were to say that, well, the way to prove or disprove the hypothesis would be to take the predictions and go out and try them.

As THE DIG at the Willow Creek anticline was drawing to an end, all of us, Bob, Jill and I, began to think about where we should go next and what we should look for. The Willow Creek anticline had been wonderfully productive, and it had been a great experience scientifically and personally for most of the people who worked on it. But it had, originally, been the result of blind luck. Marion Brandvold had stumbled onto the baby bones and then we stumbled into her rock shop. We didn't want the story to end with this one find. We didn't want it to be just a happy bit of serendipity that produced a lot of baby bones. We wanted it to be a beginning, to represent a starting point from which we and other paleontologists would go on to find more babies and more nesting grounds, to penetrate more fully the mystery of how the dinosaur babies hatched and grew, of how dinosaurs lived and evolved. We wanted to validate the find by coming up with another like it.

I was convinced that, for starters, if I stuck to the Two Medicine formation, I would find babies. In terms of geological characteristics, I wanted a site like the anticline. The new site had to have, as its predominant sediments, green or red mudstone and calichi, because these were signs of a specific kind of upper coastal plain environment. Given those characteristics, it also had to have abundant bone and eggshell fragments on the surface to make it worth exploring further.

To conduct the search I relied on several things, the first being my memory and the 20 years I'd spent poking around this and that formation in Montana. I knew where a lot of the good exposures of eroding fossil-bearing rock were in the Two Medicine formation, so I knew where to start. In some cases, I had already seen bones or eggshell during one exploration or another. (I do a lot of walking, just looking for possible fossil sites.) I also checked the geologic maps and went over reports of previous paleontological expeditions in the Two Medicine formation that had found juveniles or eggshell. Obviously, such spots would be prime for further digging, since the early paleon tologists had often just collected from the surface and moved on. From this search, several candidates for the next dig site emerged.

In 1984 Jill and I explored a spot southwest of Choteau that we called Red Rocks. We found a complete protoceratopsian skeleton, a lot of bones of baby dinosaurs, and a few eggs. I put a crew on this spot in 1985 and they uncovered more, including an adult ceratopsian and hadrosaur. But this was not our only site, nor was it the best one. Also in 1985, after a long period of negotiations, I got permission from the Blackfoot Indian Tribal Council to explore and excavate specimens from tribal lands. These included a spot called Landslide Butte. I'd picked out this site in 1984. I knew Charles Gilmore had found juvenile dinosaurs and eggshell fragments up there. And I'd visited the reservation and seen the site, so I knew it fit the bill. There were visible eggshell fragments, juvenile bones, and red and green mudstones and calichi.

Actually, I first learned of this site in the winter of 1978, before the visit to Marion Brandvold's rock shop. It was the winter after I'd found the lumpy fossil from the Two Medicine formation that turned out to be an egg. When I was trying to be sure about just what I had, I went to the Smithsonian research collection to look for comparable objects. I saw what looked to me like eggshell fragments, with no description attached. I then dug out the field diary of Charles Gilmore, who had found those fossils. He said that he thought they were eggshell fragments, and he described where he found them. That was in 1928, and the location was Landslide Butte. He never published anything on those fragments, even though he found them shortly after the widely publicized discovery of the first dinosaur eggs in Mongolia. If he had, they would have been the first reported eggshell fragments in the Western Hemisphere. Instead the honor went to Glenn Jepsen of Princeton, who in 1930 found fragments in the Hell Creek formation in Montana.

Why Gilmore did not publish that find, I don't know. Nor do I

know how he could not have seen the abundance of other fossils at Landslide Butte. Because when we finally got there, the site was so obviously rich that it seems Gilmore should have seen the fossils even if he had galloped through on horseback. After only one season there, we realized that we had found a new site that made the Willow Creek anticline look almost barren. The Willow Creek anticline had been a surprise. Landslide Butte was a shock.

In a total area of a few square miles, we have so far found two large bone beds of ceratopsian dinosaurs and three large bone beds of hadrosaurs and lambeosaurs. We've found a big ceratopsian nesting ground, the first of its kind. And, in the most astonishing discovery, we found a nesting ground of hadrosaurs that is a mile wide, three miles long and three horizons deep. That is to say, stacked on top of one another are three nesting grounds of this one dinosaur, each three miles square. And these nests are far from being sparse or hard to find. At the Willow Creek anticline, for all the bones it yielded, we had to crawl on our hands and knees to find the signs of a nest and we had to train our eyes to look for them. At Landslide Butte, the abundance is almost embarrassing. We already have hundreds and hundreds of baby bones. There are spots where, without even digging, you can literally shovel up the baby bones. Everywhere we look, we find eggs and babies. The babies range from embryonic to about four feet long, the same size range as the Willow Creek anticline.

There are red beds and green beds and calichi in this nesting ground. There are hillsides with the bones just jumping out of them. The eggs range from fragments to squashed eggs to clutches. The site is not as undisturbed as the anticline was. There was some water movement here, so many of the bones have been moved slightly and so far there are no signs of nest structure. But there are identifiable clutches of eggs and there are some skeletons that have all the bones together, so we know the water movement was not too extensive. And so far, just as in the Willow Creek anticline, what we find are baby bones only—no adult bones. Wherever we look, wherever we dig, we find baby bones. At a rough guess there could have been 500 nests in this area—500, that is, on each of the three fossil horizons.

In itself, this is tremendously satisfying. But it is, after all, a site that we went to because I had seen in Gilmore's notes a reference to eggshell fossils and thought I should follow it up. This is upper coastal plain (that's all there was when the sea was that large) but still, in order to say, "Now I know where to find baby dinosaurs anywhere in the world, now the problem is solved," you can't just go to another part of the same coastal plain where you've already found babies. You need a broader pattern. And that is what I've tried to find, at least in outline, to support my hypothesis about where to look for baby dinosaurs.

The hypothesis is simple enough. I think Charles Sternberg was right. He said to look in the uplands, the upper coastal plains. His notion was that the lower coastal plains were too wet and acidic, so that dinosaur eggs would rot or be eaten away. I think he's probably right about the reason. But I know he's right about the result.

Both the Willow Creek anticline and Landslide Butte are part of the Two Medicine formation, which is all upper coastal plain. Both of them, in the mudstone sediments I've just described, have eggs and babies. Furthermore, I have looked at other time horizons within the Two Medicine formation and found eggs and babies. For instance, the Red Rocks site, also at the bottom of the Two Medicine formation, yielded eggshell and baby bones.

The Two Medicine formation is not the only one where this is true. The red beds of Mongolia also preserved an upper coastal plain. And I made a few exploratory trips around the American West to look at other formations. I went to a part of the Judith River formation that butts up against the mountains. The terrain there is midway between upper and lower coastal plain. I found a lot of eggshell fragments, and other paleontologists (Mark Goodwin and Peter Dodson) have found more eggshell and juvenile bones. This, by the way, is just west of the spot in the Bear Paw shale where I first looked for baby dinosaurs. If I had gone west to find out where those juvenile fossils had been before they were carried to the sea, I would have ended up there.

I picked, by looking at a geologic map, another part of the Judith River formation that is an upper coastal plain. This one is in an elk habitat in Yellowstone National Park. I found eggshell fragments in the one day I spent there. I went to the Hell Creek formation, which is the latest Cretaceous, just before the dinosaurs went extinct. This was a spot where Glenn Jepsen had reported finding eggshell fragments. I searched for his location to see what it looked like. I knew it was an upper coastal plain, and when I got there I saw just what I expected: red mudstone, with plenty of calichi.

I went to the Wayan formation in Idaho. John Dorr from the University of Michigan had found eggshell fragments in this formation in 1983. This is in the lower Cretaceous. I looked at the area he found them in, and again it is an upper coastal plain with the same kinds of mudstones and calichi. Interestingly enough, the lower coastal plain there is dry, not swampy. It has red beds and calichi, too, a similar environment, but no eggshells. I don't know why that is, unless migrating habits were already instinctive in dinosaurs that lived on that lower plain. In any case, it's the upper coastal plain where the eggshells are.

After our work in Paris, Jill and I also went to sites in the south of France, one of the more beautiful environments to look at the sites where what seem to be dinosaur eggs have been found. Here, set in the middle of farms and vineyards, are little badlands the size of postage stamps, again with mudstones and again part of an upper coastal plain.

The find that probably gives me the most satisfaction is not one of my own. For a long time I'd been telling Phil Currie, a good friend and assistant director of the Tyrrell Museum in Drumheller, when he stopped down to visit our sites, that he'd find eggs and nests, too if he'd just go look in his own backyard. You see, the Two Medicine formation extends into Canada. It has traditionally been called by a different name up there (the Oldman Formation), but there's no geological reason for this; the different names are the result of confusing national boundaries with real boundaries.

Well, in the summer of 1987, Phil finally got enough time to go poking around for eggs near the Milk River, in preserved upper coastal plain. After looking for a few weeks, he and his crew found eggs. To be precise, Kevin Aulenbach found the first signs of them. When the crew investigated further, it turned out that there were about seven clutches of hadrosaur eggs. The eggs contained perfectly preserved, articulated dinosaur embryos, something nobody, anywhere, had ever seen before. Phil described the find to the press as the most important paleontological discovery in Canada in 50 years.

It's obvious. The dinosaur eggs and baby dinosaurs are in upper coastal plains. I should emphasize once again that when it comes to dinosaur fossils, the only alternative to an upper coastal plain is a lower coastal plain. All over the world, dinosaur fossils are found in one of these two kinds of deposits. Inland areas, if dinosaurs lived in them, were just not preserved by any kind of deposition. So far, lowland areas have rarely yielded eggs or babies. But the upper coastal plains have yielded and will continue to yield them. The puzzle of baby dinosaurs is solved. They're in the upper coastal plains, just as Sternberg said. I'll say it flat out. I can tell you where to find baby dinosaurs. For any geologic period during the time dinosaurs lived, on any continent on which they lived, go explore an upper coastal plain, find mudstone deposits left by stream overflow, and you'll find dinosaur eggs and babies.

Now THE BIG QUESTION: If finding these fossils is so easy, why didn't anybody do it before? It's a hard one to answer. Part of the reason lies in the relative abundance of fossils. I've talked a lot about all the discoveries we made at the Willow Creek anticline and what a rich site it was. But I've also described how we crawled on our hands and knees to look for these little bones and eggshell fragments. Except at Landslide Butte, which is a true anomaly, they don't just jump out of the ground at you. It's hard, dry work looking for bones in the Two Medicine formation. You could spend a whole luckless life walking this formation with your head way up high, five or six feet from the ground. If you didn't get down on your hands and knees, you might never find a thing.

In the Judith River formation, on the other hand, a lowland deposit, you literally walk on fossils all the time. Most of it is junk. But it's really tough to leave an abundance of big fossil bones to go prospecting on your hands and knees for these little things that are hard to find. Even after I found an egg in the Two Medicine formation in 1977, I didn't go back, partly for that reason.

Furthermore, after the 1930s, field research on dinosaurs in North America really trailed off. From the 1940s to the '70s, there were not many people looking for dinosaurs, period. Just a few, with little funding, were out prospecting. Now, with more exploration going on, the total amount of money given out by the National Science Foundation to all the vertebrate paleontologists in the country for research on dinosaurs is no more than $500,000 a year.

I can count on my fingers the full-fledged excavations for dinosaur fossils on the North American continent, and half of those are in Alberta, where the government seems to have a soft spot for paleontology. With hardly anybody out looking for baby dinosaurs, it has to be hard to find them. You have to be out looking, you have to know what you're looking for, and you have to be lucky.

As we have been, extraordinarily lucky. But there are different kinds of luck. There's the pure dumb luck that led us into Marion Brandvold's rock shop. And there's the help that you can give to luck by being prepared to recognize it when it comes. You have to know what the baby bones look like. And you have to have the luck of knowing exactly what you're looking for and of having an idea of where to look, the kind of luck Phil Currie had. It's always a treat to find new fossils and it always seems like some kind of gift when it happens, one you're never entirely prepared for. But you do prepare. And sometimes, what Branch Rickey said about baseball is true of paleontology: "Luck is the residue of design."

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