The Children's Museum is digging for dinosaurs in Wyoming. They've found amazing things.

The dinosaur footprints that cross a plot of land in rural Wyoming are deep and stunningly defined. They've been buried for millions of years underneath sediments that poured in as rivers dried up and a sea receded. The depressions are so obvious they don't require testing. 

They're neatly spaced apart, just the way the predators and herbivores planted them. They show how the animals moved, how wet the ground was when they lumbered over it. 

Put together, they're enough to make paleontologists giddy. 

The trackways, as they're called, are one of the most significant finds so far for Mission Jurassic, a $27.5 million project led by The Children's Museum of Indianapolis.

The museum purchased a 20-year lease on the square mile of land outside Cody, Wyoming, and is leading a dig that's producing multiple tons of Late Jurassic Period bones, trackways and fossilized plants that give clues to life 150 million years ago. Starting Sept. 10, the public can watch a team clean and prepare the fossils for display in the newly expanded paleo prep lab at the museum. The discoveries will be added to its popular dinosaur exhibit as it expands over the next two to three years. Plans are to put two sauropods on display in 2022.  

This summer, the museum provided a rare look at how paleontologists are finding and extracting the fossils. Going in, a team of experts knew they had a rich plot of land. But after three seasons of digging, they've discovered a repository so densely packed that it offers a clearer picture than they expected of a once-tropical ecosystem in what is now the considerably drier Big Horn Basin.

"This has so much potential," said Victoria Egerton, a scientist-in-residence at The Children's Museum.

It all began with Allosaurus bones

It started with photos of an Allosaurus that came from a rocky, sandy-colored pit on a private ranch in Wyoming. Commercial collectors had extracted the two-legged predator, known for possibly clubbing its prey with its open, inordinately wide jaw. Enough parts of the skeleton were articulated, or connected as they would've been during the dinosaur's life, that the area around it glowed with potential.  

Phil Manning, a scientist-in-residence at The Children's Museum, isn't sure what happened to that Allosaurus. But he and other experts had seen enough evidence to know that the area was stacked with dinosaurs. Word of the opportunity climbed the paleontological grapevine, where it made the short list of potential dig sites for Egerton, Manning and Dallas Evans, the lead curator of natural science and paleontology at The Children's Museum. 

The museum had decided to expand its "Dinosphere" exhibit on its 10th anniversary in 2014. It already had jaw-dropping fossils from the Cretaceous Period, which spanned 145.5 million to 65.5 million years ago. So the institution's international advisers suggested adding bones from the older Jurassic Period, president and CEO Jeffrey H. Patchen told IndyStar in March. Digging on their own meant they'd know the provenance of the bones.

The Children's Museum didn't reveal the terms of the lease contract or from whom it was leasing the land. Egerton, Manning and others from the organization officially began digging in 2017, and Mission Jurassic expanded this summer to include researchers, students and volunteers with London's Natural History Museum and the Naturalis Biodiversity Center in the Netherlands. The University of Manchester, where Manning is chair of natural history and Egerton is a research fellow, is part of the dig as well.

"Each and every institution has its own expertise," said Anne Schulp, a researcher at Naturalis. "There's colleagues who know everything about the fossil plants, colleagues who know everything about the biomechanics on how dinosaurs moved, there's people who are interested in working on dinosaur trackways, so it's really a complementary sort of thing."

The expertise made for a dig that has had about 60 people working on it at different times this summer.

The tropical western home of dinosaurs

In 1877, a teacher, a college student and a railroad worker unearthed dinosaur bones in three separate incidents in Wyoming and Colorado. The discoveries set off a subsequent bone rush. Two East Coast paleontologists, Othniel Charles Marsh and Edward Drinker Cope, were onetime friends bent on being the first to find new dinosaur species and destroying each other professionally in the process. So they hired rugged crews of mustachioed and bearded laborers.  

The men set about whacking away at the ground, tugging out as many bones as possible. In their haste, they missed environmental clues in plant fossils and rocks, misidentified bones and incorrectly christened species as new that actually weren't, according to Steve Brusatte's book "The Rise and Fall of the Dinosaurs." 

Despite the errors, Morrison Formation discoveries became so popular that they trickled into school classrooms for over 100 years and christened as stars the dinosaurs that most people know, said Rob Ross, associate director for outreach at the Paleontological Research Institution. He is not part of Mission Jurassic.

The formation has continued to deliver a bounty of Jurassic Period fossils from 150 million years ago, when the supercontinent Pangaea had begun to break into two. The formation — so defined by geologists because it has strata and rocks with a similar appearance —  dips into 13 states up and down the American West and southern Canada. 

The quarries where the Mission Jurassic team has been digging sit in the Morrison, which was laid down in a flood plain where the older Sundance Formation took shape in a marine environment 165 million years ago. The Sundance Sea had filled the basin, and newer Morrison sediments made their way in as a tongue of seaway that came down from Alaska retreated, Manning said.

“You jump millions of years when you make that step from the bottom of the notch, from the bottom of the cliff onto the Morrison rocks. It’s a huge step in time,” he said.

So far, the rocks have revealed that three river channel complexes — big enough that Manning compared them to the size of the Mississippi River — once rushed through what is now scrublands that mix barren patches with shrub-type plants. About 150 million years ago, the Jurassic Mile would have been tropical, vacillating between periods of wet and dry, Manning said.

DINO DIG: I watched paleontologists dig up bones. Here's what I saw.

A dramatic Jurassic log jam

About 150 million years ago, the powerful currents of a river channel shoved a massive sauropod carcass into a bend. Because of at least one tree trunk wedged just so, the mound of flesh, muscle and bone remained in the sand as it dried out. Any creature with a sense of smell might have cursed the trunk for contributing to such a putrid odor.

But paleontologists can thank the tree for preserving a dramatic picture of nature. Rarely do they see a fossilized log associated with bones and the plant material that protected it, Manning said. The event reveals a fuller story in the 4,000-foot upper quarry, one section of the site that scientists have worked on this summer.

The area's river channels "were moving big chunks of rock and occasional multiton bodies of bloated carcasses of dinosaurs. We’re dealing with very, very high-energy systems,” Manning said.

At this point, they don't know how the sauropod died, he said.

"It might have been such a horrific event, affecting a whole ecosystem, that nothing did chow down on these remains, which is why it's so well-preserved," Manning said.

At least two types of dinosaurs are in the upper quarry, he said. Many of the bones belong to a sauropod, and some come from the predatory theropod that had short arms and powerful legs. Not far from the log jam lays a doubled-over sauropod tail more than two dozen feet long. And near that sits a shoulder blade that's practically as tall as the average NBA player.

DINO DIG: Here are bones and fossils The Children's Museum has found in Wyoming

To extract the bones, paleontologists are digging through hard, khaki-colored sandstone while trying not to gut the fossils.

“Bones are more fragile, particularly when they’re wet," said Schulp, a professor of vertebrate paleontology at Utrecht University. "That would be like trying to chisel burger buns out of concrete and not damaging the burger buns." 

These sauropods ate like an elephant herd

During the Jurassic Period, the Morrison Formation lacked flowering plants but was packed with the ferns, conifers, ginkos and cycads sauropods ate. Questions remain, however, about their metabolism and how the landscape supported them and the smaller creatures who feasted on plants, Egerton said.

"How and why they got to be so big is a huge question," she said. "They were eating what we would consider to be very nutritionally poor foods compared to the flowering plants. But they were very, very successful, and they did this for a very long time."

Sauropods like the Brachiosaurus could weigh almost 30 tons, but they were less dense than humans, Egerton said. They had mostly hollow neck bones, similar to birds, that held up relatively small heads. 

They dined in herds, and that is astounding, considering Egerton said just one could likely munch as much as a herd of elephants.  

Fossils of Jurassic plants are rare, she said. But the museum's Jurassic Mile is producing a bounty. Egerton, a paleobotanist, has generally found plant fossils in separate layers from the bone. So far, she has found prints of bark and branches on stones that the dinosaurs might have eaten. Evidence of conifers, petrified wood and at least one leaf from a ginkgo tree will provide more clues.

Tiny stems and leaves so small they look like drips from a fountain pen are buried in mudstone. At first glance, Egerton guesses they might be fern or seed fern that were rolled into clay balls in minor flooding at the edge of a lake.

"It's basically the ultimate flower press for plants," she said.

'Science that will genuinely change how you live'

Not far from the log jam, more sauropod bones are stacked in a 5,000-foot quarry that was part of an oxbow lake. Backbones, each larger than an average-sized human hand, are wrapped together in a white field jacket. Similar to casts humans use on broken limbs, the jackets range from mere feet to hundreds of pounds, depending on the size of the fossils. They'll keep the treasures stabilized and safe during their journey. Most will come to Indianapolis, while some will go to Research Casting International in Canada for preparation and articulation. 

Dinosaur bones don't pile up in a single square mile without a reason. Preliminarily, the paleontologists know the river systems were a cause. They plan to use laser scanning technology and remote sensing through Light Detection and Ranging to create a three-dimensional map of the quarries. The data will give them an idea of how the ancient rivers moved and where the bones are relative to one another, Egerton said.

The mapping is part of what scientists will use to gather more details about what they've found. Members of the team will work with Environmental Systems Research Inc. in Redlands, California, to come up with story maps of the site. The Stanford Synchrotron Radiation Lightsource at the SLAC National Accelerator Laboratory in Menlo Park, California, will allow paleontologists to see deeply into some of the fossils with exceedingly bright X-rays.

They might find new species, specifics about where they lived or more about what went on inside the dinosaurs' bodies.

"You can look back in time through the lens of just the anatomy of the bones but also through the lens of all these other different methods, the isotopes, the study of trackways, all sorts of chemical details, the subtleties that come out of the scanning at Stanford," Schulp said.

"If independent lines of evidence sort of converge and all tell the same story, then you know you're onto something."

Together, the fossils will create a rich picture of the Jurassic Period that will educate thousands of museum visitors. More that that, Manning said dinosaur digs advance science on a number of fronts.

The team will study whether the bones show evidence of healed injuries, which could provide insight for 21st-century medicine. The site could show how the earth has been affected by the bodies, which could help further understanding of how to bury waste.

“This is a very abstract place where you think, ‘It’s a bunch of folks having fun digging bones out of the ground,’ " Manning said. "But the science that’s undertaken here is real science, impactful science, science that will genuinely change how you live.” 

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Contact IndyStar reporter Domenica Bongiovanni at 317-444-7339 or d.bongiovanni@indystar.com. Follow her on Facebook, Instagram or Twitter: @domenicareports.