by Bảo Long

The exposed slopes of the Na Dương coal mine in northern Việt Nam preserve one of Southeast Asia's richest late Eocene fossil deposits. Every newly uncovered layer offers palaeontologists a rare opportunity to reconstruct an ecosystem that flourished 35–40 million years ago. VNS Photo Phong Vũ

The night before, Nguyễn Thế Vĩnh dreamed once again that he had unearthed a crocodile.

Not just scattered bones, but a nearly complete skeleton, perfectly preserved, resting beneath the earth of the Na Dương Basin for more than 30 million years. In his dream, he gently brushed away layers of soil and carefully lifted the fossilised skull with both hands.

The next morning, the dream still lingered as he and his colleague, Nguyễn Minh Chuyển, both palaeontologists from Lạng Sơn Provincial Museum, set off on their old motorbike toward the Na Dương coal mine.

The road snakes through slopes coated in grey coal dust. In the sweltering summer heat, layers of red and yellow earth reveal a geological record stretching back millions of years. No crocodile awaited them that day, but only the quiet hope that a fresh excavation or recent downpour might reveal creatures long hidden from the sun.

It is a hope that keeps drawing them back.

"In the palaeontology community, the Na Dương Basin is considered one of Southeast Asia's richest fossil sites," Chuyển said.

"The late Eocene sediments here preserve an entire ecosystem from 35 to 40 million years ago, a vast landscape of lakes, swamps and forests teeming with crocodiles, turtles, coal beasts (anthracotheres) and diverse plant life."

Chuyển's assessment is echoed by international researchers who have spent years studying the basin. In a landmark review of the site, Prof. Madelaine Böhme, a German palaeontologist and terrestrial palaeoclimatologist at the University of Tübingen, described Na Dương as "one of the few localities in Southeast Asia allowing for multi-focused investigation" of Eocene ecosystems, citing its extraordinary diversity of vertebrate, invertebrate and plant fossils.

For Vĩnh and Chuyển, every expedition is more than a search for museum specimens. Each fossil is a potential piece in reconstructing a vanished world.

Into the mine

Mining has made many of Na Dương’s fossil discoveries possible by exposing sedimentary layers that would otherwise remain buried. Yet it is also steadily erasing the landscape in which those fossils have survived for millions of years. With limited personnel, equipment and time, palaeontologists must reach each newly exposed section before machinery, rain and exposure to the air destroy the evidence it contains.

Palaeontologists Nguyễn Minh Chuyển (right) and Nguyễn Thế Vĩnh begin another day of fieldwork, descending into the open-pit mine where newly exposed sediment layers may reveal fossils preserved for tens of millions of years. VNS Photo Phong Vũ

They parked at the edge of the sprawling mining site and shouldered backpacks filled with basic tools: hammers, chisels, small brushes, specimen bags, water and packets of peanut candy to keep them going through the day.

After a quick exchange, they split up, each taking one side of the exposed slope. Heads bowed, they walked slowly, eyes scanning the rocky ground.  

There was no high-tech equipment, no ground-penetrating radar. They relied solely on experience and subtle clues: a fossilised leaf imprint, a petrified tree trunk or traces of ancient crocodile dung.

Palaeontologist Nguyễn Thế Vĩnh scans the exposed slopes for subtle clues, a change in colour, texture or shape, that might reveal fossils hidden beneath the surface. Years of experience have taught him to read a landscape that most people see as nothing more than rock. VNS Photo Phong Vũ

"Spotting fossils here is extremely challenging," Chuyển said.

"They blend almost perfectly with the coal and surrounding rock. We have to follow surface signs before focusing on a promising area."

After three years of regular surveys, the two men know the terrain intimately. What others see as mere dirt walls cut by excavators, they recognise as sedimentary layers dating back tens of millions of years. Unusual colour streaks, fissures or oddly textured fragments are enough to stop them in their tracks.

With only simple tools such as geological hammers, chisels and brushes, the team carefully removes layers of rock to avoid damaging fragile fossils preserved within the ancient sediments. VNS Photo Phong Vũ

Yet even deep familiarity cannot guarantee success across a 1,000-hectare site. Some days, they hike for kilometres under the sun, finding only broken fossils. Other days, promising trails disappear into rubble.

Still, they return whenever they can. In palaeontology, the work consists mostly of patient searching. Actual discoveries are rare.

By the fifth day, exhaustion was etched on their faces. As usual, they separated at the edge of a freshly exposed seam. They moved methodically, crouching for long stretches to examine shale layers before moving on. 

Near noon, amid the vast silence broken only by distant excavators, Vĩnh's voice rang out.

'We can't save it'

Following their unspoken rule, Chuyển quickly packed his gear and hurried over. At Vĩnh's feet, a brownish-white shape protruded from the damp soil. One glance told them it was a large turtle shell, bigger than most they had found in Na Dương.

Without a word, Chuyển handed over a chisel. They worked with painstaking care, lightly tapping and brushing away dirt. But as the shell emerged, both men saw what they had feared. Exposed to moisture for too long, the fossil had become brittle and porous. With every layer of soil removed, small pieces crumbled away.

Vĩnh stopped. He stared at the damaged shell for a long moment, then shook his head.

"What a shame," he said. "It's so large, but we can't save it."

Moments after uncovering a large fossilised turtle shell, Nguyễn Thế Vĩnh realised it could not be saved. Prolonged exposure to moisture had left the specimen too fragile to survive excavation. VNS Photo Phong Vũ

Experience had taught them not to push further. They photographed the find, recorded its coordinates and gently reburied the site. A remarkable fossil had been discovered, yet it could not be taken.

The fossil remained where it had lain for millions of years. Too fragile to survive excavation, it was photographed, mapped and carefully reburied, preserving its context for future research. VNS Photo Phong Vũ

The disappointment passed quickly. They picked up their tools and continued.

Vĩnh returned to an area rich in fossilised crocodile dung, convinced something more lay buried below. On the other side of the site, Chuyển shifted his search toward coal seams where anthracothere remains had appeared before.

A cluster of fossilised crocodile droppings, or coprolites, convinced Nguyễn Thế Vĩnh to keep searching this section of the mine. To palaeontologists, such traces often signal that more complete fossils may still lie hidden in the surrounding sediments. VNS Photo Phong Vũ

Their familiar rhythm resumed: walk, observe, move on.

"Sometimes we feel incredibly tired," Vĩnh admitted. "But the possibility of finding an intact specimen keeps us going."

After hours searching under the summer sun, palaeontologist Nguyễn Thế Vĩnh pauses to rest. Most field surveys end without a significant discovery, making patience one of the most essential tools in palaeontology. VNS Photo Phong Vũ

A fragile find

Late that afternoon, their persistence was rewarded. At another freshly exposed section, Vĩnh uncovered a second turtle shell, which was almost perfectly intact. Not long after, Chuyển found a tooth and a suspected limb bone from an anthracothere. The specimens were modest in size, but they meant the expedition had not been in vain.

Each strike must be measured. Fossils exposed to air and moisture can become extremely fragile, making excavation a slow process that demands patience and precision. VNS Photo Phong Vũ

Vĩnh carefully brushed away the remaining soil and wrapped the fossils in protective padding. For the first time in days, broad smiles broke across both men's faces.

A smile finally breaks across Nguyễn Thế Vĩnh's face after uncovering an intact fossil still embedded in rock. After days of searching with little success, discoveries like this make every expedition worthwhile. VNS Photo Phong Vũ

The satisfaction of making a discovery goes far beyond simply returning with specimens. For Vĩnh and Chuyển, the most profound feeling is the quiet realisation that they may be the first humans to lay eyes on these creatures since they were buried tens of millions of years ago.

Smiles break across the faces of Nguyễn Minh Chuyển (right) and Nguyễn Thế Vĩnh after recovering a nearly intact fossilised turtle shell. After days of searching, moments like these make every setback worthwhile. VNS Photo Phong Vũ

"When I finally hold a fossil in my hands, I feel incredibly happy. It makes all the hard work worthwhile. And then I realise something extraordinary. I may be the first person to see this animal since it was buried 30 or 40 million years ago," Vĩnh said.

Fossilised crocodile teeth (left) and a suspected coal beast (anthracothere vertebra) are measured and documented before being sent to the Lạng Sơn Provincial Museum. Even fragmentary remains can provide valuable evidence for reconstructing Na Dương's ancient ecosystem. VNS Photo Phong Vũ

"From 2021 to 2022, Lạng Sơn Provincial Museum conducted surveys, but it wasn't until 2025 that we found a number of valuable specimens, including those that are rarely discovered elsewhere in the world, such as the jaw specimen of an anthracothere," said Nguyễn Gia Quyền, head of the Curatorial Department at Lạng Sơn Provincial Museum.

"In particular, that anthracothere fossil is the first of its kind to be acquired by the Lạng Sơn Museum. It can be said that this is a highly valuable artifact for the research efforts of palaeontologists and archaeologists."

In the Na Dương Basin, layers of black coal, red earth and yellow clay stack upon one another like the pages of an immense history book. Every fossilised leaf, every fragment of petrified wood and every bone weathering out of the hillside tells the story of a world that existed long before humans ever walked the Earth.

Vĩnh still remembers the first time he set foot here. "It felt completely different," he recalled. "As if I had stepped into another world. Na Dương is unlike anywhere else. It almost feels like another planet."

Steep terrain and constantly changing excavation faces make fossil hunting physically demanding. Yet every newly exposed layer offers another opportunity to uncover traces of life from the late Eocene. VNS Photo Phong Vũ

Perhaps that feeling is why they keep returning.

"We always hope to discover more specimens," Vĩnh said.

"The richer the museum’s collection becomes, the more complete the story we can tell."

For Vĩnh and Chuyển, collecting fossils is not simply an act of scientific curiosity. It is a race to document a disappearing record.

“If these fossils are not collected and preserved now, future generations may never know what this land once looked like or what kinds of life flourished here,” Chuyển said.

Nguyễn Minh Chuyển (right) and Nguyễn Thế Vĩnh compare the fossils they have recovered during the day's survey. In a profession where days of searching often yield little, every new discovery is a shared triumph. VNS Photo Phong Vũ

Racing time

Every day, excavators remove another section of the basin to reach the coal below. Newly exposed slopes offer fresh opportunities, but only briefly. Some fossils are shattered by machinery. Others crumble after days of exposure to rain, heat and humidity.

That is why the two palaeontologists return whenever they can. They do not expect every expedition to produce a remarkable specimen. Often, several days of searching yield only fragments, or a discovery too fragile to be removed. But each visit gives them another chance to rescue a small part of the distant past.

While Vĩnh and Chuyển toil in the field to unearth specimens, their superiors back in the office grapple with burdens of their own.

"Regarding time and the funding allocated for these tasks, they remain limited. Therefore, every year, despite the low budget, we still make every effort to conduct surveys and research in order to discover and retrieve as many artefacts as possible to bring back to the museum," Quyền shared with Việt Nam News.

Recognising the importance of the Na Dương Basin, Lạng Sơn Province has incorporated it into the Lạng Sơn UNESCO Global Geopark, which in 2025 became Việt Nam's fourth UNESCO Global Geopark. The designation reflects the region's geological significance, including a fossil record that offers a rare glimpse into Southeast Asia's ancient ecosystems.

The Na Dương Coal Company has also worked with museums and research institutions to facilitate fossil collection and fieldwork in the area.

But the basin is vast, geologically complex and still only partly understood. Unlocking its scientific potential will require more than access to the mine. It will require sustained investment in researchers, equipment and the technical expertise needed to document and preserve what lies beneath the ground.

As mining continues to reshape the landscape, Vĩnh and Chuyển return whenever they can, racing against time to document and preserve fossils before they disappear forever beneath heavy machinery or the elements. VNS Photo Phong Vũ

Evening came quickly over Na Dương. Excavators continued moving across the mine as Vĩnh and Chuyển wrapped the day’s specimens in protective padding and secured them inside their backpacks.

By the next morning, another layer of earth would have been stripped away and another chapter of the basin’s history exposed.

Somewhere beneath the ancient sediments, perhaps the crocodile from Vĩnh’s recurring dream was still there, waiting in the darkness.

But at Na Dương, nothing can wait forever. — VNS