Heaving and splitting rocks are all in a day's work for fossil diggers at Germany's Messel pit. The pay-off is finding the world's most exquisitely preserved fossils.
After unlocking an iron security gate, paleontologist Sonja Wedmann points her four-wheel-drive down a bumpy road. It leads to the bottom of the Messel pit. With its 48 million-year-old fossils, Messel is the richest site in the world. It is also possibly the best place if you want to understand a period called the Eocene when mammals started emerging after the extinction of the dinosaurs.
As we drive down the pit, Wedmann points out piles of bleached rock tailings left behind by a century of coal and oil shale mining.
Mining stopped at Messel in 1970 and the disused pit was then slated to be used as a garbage dump. But following a long and bitter fight by the scientific community and locals, it became a UNESCO World Heritage Area in 1995 and is now reserved exclusively for fossil research.
Wedmann parks her van next to a group of fossil diggers from the Senckenberg Research Institute. They have been hard at work since seven o'clock in the morning.
Wearing mud-smeared blue overalls and stout work boots, fossil preparer Bruno Zehr stands on a steeply-inclined outcrop of oil shale. He uses his spade to hack off large chunks of shale from the underlying rock bed and slides the pieces down the slope, where they are heaved onto wheelbarrows by his co-workers.
Once their wheelbarrows are full, the fossil hunters sit on plastic chairs, wedging apart thin layers of rock sediment with yellow-handled kitchen knifes. The air is filled with the sound of discarded oil shale being flicked onto the ground.
Messel is about 35km southeast of Frankfurt in central Germany. It was formed when a violent volcanic eruption created a crater that filled with water, creating a deep lake.
Tens of thousands of preserved plant and animal species - from water lilies to beetles, bats, birds, fish, hedgehogs and crocodiles - have been excavated from the sediment layers that once formed the bed of the ancient lake.
"You have to imagine the oil shale as if it is a sealed book where the pages are stuck together," Zehr says as he slides his knife expertly between two thin layers.
"In between the pages, that is in between the rock layers, is where you find the fossils."
Zehr pulls out his magnifying eye glass to take a closer look at a tiny dark dot on a piece of shale. It's a palm fruit. These days, the closest palms grow a thousand kilometers away. But Messel was once surrounded by dense, subtropical jungle that was much wetter and warmer than the current climate.
Hard work worthwhile
The fossil hunters sit in the sun and split rocks for hours at a time - that is when they are not digging up rock.
Geography student Juliana Kehrer is just finishing up a four-week internship with the Senckenberg Institute. Kehrer has a sore back from lifting rocks and aching hands from splitting shale. But she says discovering once living animals in the rocks is just "amazing."
"At first you just see old rocks and suddenly there is a small animal on the rock in front of you. I found old spiders and it was just really nice," says Kehrer, waving her knife for emphasis.
Sonja Wedmann walks over to two buckets filled with water to see what fossils the group has found today. The fossils are kept under water. As she fishes out a palm leaf fossil, Wedmann explains the fossils need the water because the oil shale is also high in water.
"If it dries out, [the rock] cracks and all fossils which are on the surface also crack and are destroyed," says Wedmann.
It seems strange for the fossils to be sitting in white plastic buckets. They are some of the world's most famous fossils and have been preserved exquisitely. Not only have the researchers found whole skeletons here, but also - on rare occasions - the preserved outlines of fur, feathers and skin - as well as stomach contents and even the foetus of an ancient horse still in its mother's stomach.
Bruno Zehr walks up, brandishing a tiny fish fossil.
"See here is the backbone and the tail is there too," says Zehr as he traces the pale skeleton with his finger.
He will measure the fish fossil and enter it in the log book before wrapping it in wet newspaper where it will stay until someone finds the time to prepare it during the winter months when the rain and snow make excavating too dangerous and too cold.
As he sits back down in his chair, Zehr says the job requires steady hands, a light touch and an enormous amount of patience. It seems the fossil diggers here have that in spades - or should that be trowels?
Author: Kate Hairsine, Messel
Editor: Zulfikar Abbany