This is the largest land-dwelling bug to have ever lived.

Imagine walking through a peaceful forest and running into a huge prehistoric creature, like this enormous, six-foot-long millipede.

During the Pennsylvanian period, massive bugs roamed North America and Europe. And the largest was the Arthropleura.

Arthropleura is an extinct giant millipede that lived around 315 to 299 million years ago during the late Carboniferous period. That's the age before dinosaurs.

Its name translates to "Jointed rib," which refers to its segmented body.

Arthropleura's flattened body comprises approximately 30 jointed segments. And two side plates and one center plate cover each section.

The ratio of legs to the body segments is approximately 8:6, similar to some modern-day millipedes.

How Big Was This Arthropleura?

Scientists believe it grew up to at least 2.6 meters wide and 8.5 feet long. It was the creepy, 'millipede king of the forest.'

If an average-height man lay down on the ground, an adult Arthropleura could completely cover his body.

Some researchers even describe it as the largest land-dwelling arthropod (invertebrate) to ever walk the Earth.

However, scientists are yet to find a complete large individual of Arthropleura. They're only studying a partial body fossil from southwestern Germany that has a length of 90 cm.

Despite its large size, Arthropleura is an herbivore. Scientists have found spores from plants like ferns in fossil fragments.

Its Tracks Alone Show How Massive It Grew

During fossil excavations, scientists often find fossilized tracks from ancient creatures. And Arthropleura is no different.

One researcher, Michael C. Rygel, snapped a picture of the millipede's huge tracks in Nova Scotia (Canada).

The tracks don't only reveal the millipede's size but also give some clues about the creature's habitats.

Some of the prehistoric tracks showed Arthropleura skittering around trees in the forests where it thrived.

Arthropleura Had No Known Predators

It's hard to imagine a millipede at the top of the food chain, but Arthropleura had no known predators. Scientists established that fact by looking at the creature's body armor.

Researchers Carsten Brauckmann, a prehistoric arthropod specialist, and Otto Kraus, a millipede expert, uncovered a surprising fact.

These scientists found that the Arthropleura's armor was quite thin. The plating was just a few millimeters thick.

And unlike the exoskeletons of modern crustaceans, it didn't contain hard calcium carbonate.

This evidence indicates these creatures had few, if any, enemies that tried to catch and eat them.

The Creatures Likely Went Extinct Due To Climate Change

Arthropleura went extinct during the Permian Mass extinction. Earth started losing oxygen, and the very gas that created these giant bugs was disappearing.

Earth also began getting hotter and drier due to volcanic activities. The swamp and forests that once supported life became deserts.

The Permian Extinction was Earth's most severe extinction. It wiped out 90 percent of all life on Earth.

This mass extinction affected insects and, as a result, gave way to the rise of the dinosaurs.