Walking on Eggshells in the Argentinian Desert

Millions of years ago, before the Andes Mountains rose to the west and the Atlantic Ocean grew wide to the east, dinosaurs bigger than city buses gathered here by the hundreds to lay their eggs.

Something lured them to this place year after year, but at a terrible price. The rivers flooded again and again, covering the eggs and drowning the embryos within. Over eons, deposits of mud buried the eggs so deep that it seemed their story would be swallowed by the earth.

But then the process reversed itself. Fast-moving water tore through here, scooping out millions of years of sediment and exposing layers of ancient soil. Finally, this remote area of Patagonia turned into badlands resembling the American Southwest, with expanses of red earth spreading for miles between buttes.

Erosion had taken its turn. Now it was time for pickaxes, shovels and chisels. It was time for Luis Chiappe and his crew of 15 students and scientists to dig down a few feet and look back about 80 million years.

*

One morning in March, Chiappe (pronounced kee-AH-pay) shook a can of fluorescent red paint and sprayed a broken line 6 feet below the crest of a steep butte. The line meant “tear here.”

Just below the paint, about 80 feet above the desert floor, coin-size fragments of fossilized dinosaur eggs lined the side of the butte like the meat in a burger.

Chiappe’s line marked how deep the crew could dig from the top without disturbing the eggs. Once they reached the line, once they had removed the top bun of the burger, they would meticulously pick down the rest of the way with chisels and brushes.

On the desert floor, thousands of dinosaur-egg fragments lay on the surface; anyone who knew what to look for could simply pick them up. But wind and water had scattered them, so they couldn’t tell Chiappe many of the things he had come here to learn.

Did these plant-eating monsters lay eggs in nests or randomly on the ground? Did they bury the eggs or just leave them on the surface? Did more than one species lay eggs here? Did the foot-long hatchlings hang around or leave quickly? Did the adults watch over them or just walk away?

For answers, the scientists needed to unearth the site as it had been when the eggs were laid somewhere between 70 million and 90 million years ago. That was the main task for the expedition headed by Chiappe, an associate curator of vertebrate paleontology at the Natural History Museum of Los Angeles County. The expedition was organized by that institution and the Carmen Funes Municipal Museum of Plaza Huincul, Argentina.

Shump . . . shump . . . shump . . . the work was easy at first, shovels scooping up the dirt and sailing it over the sides of the butte.

But then the crew came to hard, red mudstone. They spread out, 10 of them over about 400 square feet, swinging picks and shoveling the rocky debris. Shovels clanged. Pickaxes got stuck in the ground.

As they worked in the heat, the wind howled. When one crew member opened his canteen, its mouth hooted like an ocean liner. At times like these, the vultures need only spread their wings to shoot straight up like party balloons.

*

It was lunchtime, on the second day of the dig, when Chiappe was handed a sandwich bag containing 30 white chunks of rock. Alberto Carlos Garrido, 27, an Argentine member of the expedition, had spotted them on the desert floor.

Chiappe, sitting in the shade of a black tarp stretched between two vehicles, put down his orange. He examined each chunk, then tossed them one by one over a table filled with crackers, tuna and sardines to Argentine paleontologist Rodolfo Coria.

Some were bits of dinosaur tailbone, but not from the titanosaurs, the huge plant eaters believed to have laid the 6-inch-wide eggs. What creature had this tail belonged to?

Suddenly the expedition took a turn. There was something else to dig for besides eggs.

Chiappe and his colleagues had discovered the dinosaur nesting area nearly 1 1/2 years ago, and their preliminary exploration had already uncovered two startling finds.

Some shell fragments they had collected contained rarely found bones of dinosaur embryos. Other fragments contained fossilized dinosaur embryo skin--the first confirmed find ever.

Dinosaur eggs have been found in at least 200 places around the world. But this new site, with thousands of eggs scattered over a square mile, seemed to offer a rare opportunity to find more embryonic bones and skin, as well as clues to dinosaur reproduction.

So now the scientists were back in this desolate place of widely scattered ranches and scrubby bushes, some with needles tough enough to pop tires. The closest place to buy gas was 60 miles away.

Chiappe, a 36-year-old Argentine about 6 feet tall with beard and thinning black hair, presided casually over this dig. He seemed more the thoughtful big brother than the boss, taking orders for cigarettes before a run into town, leading the applause for the night’s cooks. When he showed up in camp with an ice chest full of cold beer one day, he threw open the lid with glee, as if he’d just gotten in from Stockholm with a Nobel Prize.

At the spot where the bits of tailbone were found, Chiappe and Coria sat on the ground, probing the crumbly dirt.

“Ah!” Chiappe declared, after just a few minutes of slicing dirt with his big knife. He held up a squat white cylinder about the size of his fist. A piece of tailbone.

“We found a monster,” Chiappe said, “or a part of it.”

He and Coria laughed in delight. It was the laugh of colleagues who have spent many hours together in the field.

Sweeping with a wide paintbrush, Chiappe uncovered a second tailbone, still lined up with the first after millions of years. Were more bones waiting, still aligned as in life?

Chiappe started in with both hands, one wielding the knife, the other the brush. Coria chipped away with a dental pick. They found a third tailbone, and then a fourth, the trail leading them straight into a low hill.

“It could be a portion of the tail,” Chiappe said, “or it could go all the way to the last tooth.”

*

It was the second day of shoveling at the butte. Gerald Grellet-Tinner, 42, a long-haired, high-spirited French-Swiss citizen studying at the University of Texas at Austin, turned over a chunk of rock and saw the stop sign: eggshell.

The crew dropped their shovels and pickaxes and took up hammers, chisels and brushes. Clanging of shovel on rock gave way to a delicate tink-tink-tink, as if a chain gang had taken a break for sculpture class.

Crew members pried up rocky chunks the size of pocket watches, looking for more gray bits of shell. After millions of years, the remains have been reduced to fragments, many no bigger than a fingernail, held in egg-shaped patterns by the mudstone.

On this day, the wind was gone. Working with her hammer and chisel, Natalia Kraiselburd, a 24-year-old student at the University of La Plata in Argentina, softly hummed the theme from “The Flintstones.”

She dug mostly in the afternoons. Mornings, she was assigned to wander alone on the desert floor, searching for some of the rarest fossils in all of paleontology--fossilized dinosaur embryo skin.

Here and there, patches of it line the interior of an egg fragment. But it is extremely difficult to see, even when it is pointed out. Jam a sample up to your eyes or whip out a magnifying glass and you might detect the telltale pebbly surface.

Kraiselburd needs no magnifying glass. She has a rare ability to spot tiny things. Her brown eyes peered through her wire-rimmed glasses as she wandered the desert, looking as if she were browsing a flea market.

When palm-size chunks of shell caught her eye, she squatted and picked them up. Whenever a piece seemed promising, she sat in the dirt and held it inches from the bill of her aqua-colored baseball cap, turning it this way and that, playing with the angle of sunlight. She scraped dirt from it with her knife and sometimes dribbled water on it from her bottle. Most of the time, she let the shell fragment fall back to the earth and moved on.

But by the end of each day, she had several samples for Chiappe and Coria. Each man immediately reached for a small magnifying glass to examine them.

Kraiselburd waited patiently, like a student waiting for a grade. She didn’t look at the skin. She’d already seen it.

*

The day after Coria and Chiappe uncovered the tailbones, Coria returned with Elizabeth Chapman and Anwar Janoo, who started troweling away the dirt uphill of the bones so it wouldn’t cave in on the excavation.

“Slowly and carefully,” Coria cautioned. There was no telling where the next bone might pop up.

Sure enough, Janoo found a light brown bone about the size of a pocket watch in the debris he was troweling aside.

“Go carefully,” Coria repeated.

Whisking away dirt with her brush, Chapman followed the tail as it curved to the right into the hill. In a half hour, the exposed tail lengthened to 2 feet, with no sign where it would end.

It was becoming clear that the remains were of an adult lying on its right side. They didn’t belong to a four-footed plant eater such as the ones that laid the eggs. Perhaps they belonged to a two-legged plant eater called an ornithischian, or perhaps even a meat-eating theropod.

That would be a prize; a good skeleton might shed new light on theropod evolution.

Like the dinosaur, Coria, 39, lay on his side, totally focused as he poked in the dirt. At one point he reached down and jiggled his pants leg. A wasp staggered out. Yes, he acknowledged, it had stung him. He’d shown no reaction.

A sixth tailbone appeared, and then a seventh. Coria began picking dirt away from the bottom sides of the tailbones and found what he was hoping for: slender, foot-long bones called chevrons that hung down from the vertebrae. Their presence was a sign of good preservation.

But as he worked his way back down the tail to expose more chevrons, he grew puzzled. Usually chevrons are all the same shape. But on this animal, one curved like a boomerang and the next one was straight. Some were connected to the tailbones in unexpected places.

“What is going on here?” Coria mused.

“OK,” he said, about two hours into the day’s dig. “Let’s go for the pelvis.”

In minutes, Janoo’s brush uncovered the first trace.

Less than two miles away, other crew members had to use hammers and chisels to break mudstone covering the eggs. Here, in this clay, the dirt fell away easily.

By lunchtime, a 4-foot-long section of tail was exposed, and the 2-foot-long pelvis lay in the dirt like half-buried ancient pottery.

*

At the butte, the digging had exposed about 200 eggs. From them, and from a similar dig about three-quarters of a mile away, one thing was clear: The dinosaurs had laid their eggs in clusters. But there was no sign that the creatures had built nests from twigs or other material.

Some eggs were found piled on one another, so Chiappe figured they were probably laid in depressions in the soil. However, he couldn’t be sure if the hollows were natural or if the dinosaurs dug them, nor could he tell if the creatures had covered the eggs.

One clutch of about 20 eggs contained remnants of 11 embryos, a sign of the catastrophe that had struck here.

Near the egg quarry, Janoo, a 42-year-old researcher from the American Museum of Natural History in New York, made a startling discovery: small bones on top of some eggs, almost touching them.

They didn’t look embryonic. Were they from a hatchling, indicating that the newly hatched dinosaurs lingered at the nesting grounds? Or were they from some creature that had come to feast?

*

Following the dinosaur bones into the hill, Coria and co-workers uncovered a club-shaped ischium bone extending from the pelvis; a right leg and foot; ribs; neck bones; a left shoulder. There was also a diminutive left arm with a claw. The upper arm was about the width of two fists.

Coria tossed his brush in the air in elation.

But the skull still eluded them. After lunch on the second day of the excavation, Chiappe took another run at finding it.

He slapped his palm on the dirt, marking the spot he’d chosen to dig. He took his brush to the dirt and in a few minutes said, “Ah, here we go.”

It was bone, but only tiny pieces. Another digger found an inch-long piece of finger-width bone in the same place. But five minutes later, Chiappe called a halt.

They’d found only a couple of dozen tiny fragments. If they came from the skull, it was too damaged to recover this way. The diggers would wait for an expert on fossil preparation who might be able to assemble this jigsaw puzzle.

That is, if there were enough puzzle pieces left. Maybe an ancient predator had beaten them to this prize.

No matter. This find was a trophy.

It was definitely a kind of theropod. It had been 19 feet long in life, a size suggesting it might be a previously unknown species.

Before dinner one night, Chiappe popped the champagne in camp as everybody gathered in a circle.

“Let’s celebrate the success of this magnificent team,” he said.

Then he looked at his old friend Coria. Coria looked back at Chiappe.

Neither knew what more to say.

So they laughed.

*

After a month, Chiappe and his crew struck their tents and headed home.

Next would come long hours in laboratories to analyze the theropod skeleton, the tiny bones Janoo found with the eggs, the skin samples spotted by Kraiselburd’s sharp eyes.

But the Patagonian desert has not given up all its secrets. Year after year, the scientists will return here, just as the dinosaurs did.