The biggest bug to ever live has been found in Germany, but don't panic: It's been dead for 390 million years. From the tip of its massive claws to the end of its tail, the prehistoric beast -- a sea scorpion, thought to be an aquatic ancestor of modern scorpions and spiders -- was 2.5 meters long and weighed as much as two men.

In a paper published Tuesday in the British journal Biology Letters, a team of researchers led by University of Bristol paleobiologist Simon Braddy describe the creature, which is named jaekelopterus rhenaniae.

The sea scorpion's body alone stretched 2.5 meters. Braddy estimates it weighed in at 180 kilos, too big for its spindly legs to support it on land. Instead, it used a powerful tail and a pair of wide hind legs as paddles to cruise through prehistoric seas and rivers hunting for prey.

Unlike modern, land-dwelling scorpions, the sea scorpion had no stinger. "It used its claws to catch prey," Braddy told SPIEGEL ONLINE. "It would lie in wait near the sea floor and when a fish or another creepy-crawly came along, the scorpion would lunge forward and rip it to pieces."

The 46-centimeter fossil was discovered in a rock quarry near Prüm in western Germany. Markus Poschmann, an excavator for the Mainz Cultural Heritage Directorate, discovered the fossil. "I was loosening pieces of rock with a hammer and chisel when I suddenly realised there was a dark patch of organic matter on a freshly removed slab," Poschmann said.

"After some cleaning I could identify this as a small part of a large claw. Although I did not know if it was more complete or not, I decided to try and get it out."

After careful excavation, Poschmann removed a large slab of rock that contained a full claw. After cleaning and piecing together the fragments, Poschmann knew he had discovered something unusual.

To reconstruct the animal's size, the team relied on past finds. "We've found smaller versions of the same animals in the past," Braddy said. Based on the claw, the researchers were able to calculate how big the rest of the animal was by using smaller finds as a guide.

Sea scorpions were related to spiders, and have been extinct for hundreds of millions of years. But long before they died out, some sea scorpions made the slow creep up onto land, evolving larger legs and a different set of claws. Fossils show that scorpions as long as a meter once crawled the Earth.

The newly-discovered sea scorpion lived at a time when giant insects were a common sight. Between 460 and 255 million years ago, the sea scorpion shared the Earth with two-meter long millipedes and dragonflies with wings 75 cm long. Higher levels of oxygen contributed to the Brobdingnagian bugs, as did competition with other arthropods.