The Arthropleura was an arthropod commonly referred to as the most giant millipede of all time. It had only five species, and they are all extinct. It originated during the late Carboniferous period. The Arthropleura existed before the dinosaur, about 345 to 290 million years ago. They were one of the largest terrestrial species during this period. They are closely related to the modern-day millipede. The Arthropleura dominated the swampy forest of North America during the Pennsylvanian period, a sub-era in the Carboniferous period. In this article, we’ll take a historical journey into the life and extinction of the 8-foot giant millipede that once roamed the earth. Read on!

Description and Size

The Arthropleura, meaning “jointed ribs” in Greek, is a genus of extinct large millipedes, belonging to the phylum Arthropoda. Being an arthropod, the Arthropleura is characterized by a well-developed, jointed dorsal exoskeleton, known as a tergite.

It had a flat, long, segmented body, which was composed of two large antennae located on the head. Each segment of its body contained three armor plates, one on the ventral part of its body and the other two lying by its sides. This served as a protective layer from environmental hazards.

It can be identified by its brown/black colored bodies, which are lined with yellow at the distal parts of each segment. The head is not distinctly known. However, it was believed to be covered by the first tergite, which later turned out to be the collum or neck.

The Arthropleura was believed to have been Diplopodous, such as the millipede. It had two pairs of legs attached to an individual tergite. Fossil analysis shows that it had up to 28 to 32 jointed bodies. That means it had about 112-128 legs in total.

It has three ventral plates, namely the K, B, and rosettes plates, which were thought to be the animal’s respiratory organs.

How Large Was the Arthropleura?

As you must have guessed by now, the Arthropleura was one of the largest arthropods to ever roam the Earth. With a size of about 2.0 to 2.6 meters (6 to 8 feet). This is about the size of a small car today.

A study suggested that the Arthropleura weighed about the same size as a large dog, about 50 kg (about 110 lbs). During the Carboniferous period when the Arthropleura existed, the oxygen available on Earth was around 51%. This high level of oxygen contributed to their enormous size.

The Arthropleura would most likely not have survived in this modern world, with about 21% oxygen available.

• Weight: 110lbs (50kg)
• Length: 2 to 2.6 meters
• Skin: Thick exoskeleton
• Legs: 112 to 128 legs

Diet – What Did the Arthropleura Eat?

The Arthropleura was an herbivore. There’s no conclusive evidence for this, but a study has shown that Arthropleura may have fed on larger plants, fruits, and seeds because of its size. They had strong jaws to crack seeds and break large fruits and dead wood.

Another study about possible gut contents from an Arthropleura showed gut contents that were made of debris from the tree-like club mosses, which were a significant component of the coal swamp vegetation.

Although, another study showed that the Arthropleura’s diet consisted of mostly plants. It was possible that the Arthropleura was carnivorous during its juvenile stage. This is because the ability to digest plants properly was discovered not to have been developed until they matured.

Habitat– When and Where the Arthropleura Lived

The Arthropleura existed about 345 to 290 million years ago. From the Visean stage of the Carboniferous Period to the Sakmarian stage of the lower Permian period. It lived alongside other animals like some primitive reptiles and giant amphibians.

It was once thought that the Arthropleura lived in the coal forests. However, fossil trackways were found in the Carboniferous rainforest after its collapse. This is now modern-day North America and Europe.

This region is close to the equator, and it is covered by various richly vegetated swamps. This was the home to the Arthropleura and many other large arthropods, like the dragonfly.

Threats and Predators to the Arthropleura

As a result of its size, the adult flat-walking giant had no known predator during its period of existence.

The Arthropleura was a solitary creature. It was simply on top of its food chain. It had thick, tough, and wide back armor plating as its defense, and its strong jaws could deliver a nasty bite. However, it is unlikely that the walking giant may have been poisonous.

The Arthropleura’s environment is its primary threat. Sharp large rocks could easily impale the walking giant. Also, Carboniferous storms could be devastating to the Arthropleura. The Arthropleura’s strong body armor couldn’t protect it from the Carboniferous forest fires. So, the animal would often make an escape from the fire or crouch for cover on the ground, and most of the time, it gets burned alive.

Arthropleura: Defense

The Arthropleura’s armor was its best defense. It was naturally mildly aggressive and, when challenged, like the cobras, the Arthropleura could lift its upper body, so it looks massively tall—tall enough to look a grown man right in the eye.

But, this defense strategy is unsafe, as it exposes its soft innards to potential attack.

Like modern millipedes and centipedes, they can secrete pungent-smelling cyanide. This help keep their enemies away.

Discoveries and Fossils – Where Arthropleura Fossils Were Found

The first fossil discovery of the Arthropleura, Arthropleura armata jordan and armata meyer, was in 1854. There are many fossil tracks on the coast of Scotland in the Isle of Arron.

Recently, researchers discovered a new Arthropleura fossil dated around 326milion years old. It was inside a fragmented block of sandstone located on a beach in Northumberland, Northeast England.

The exoskeleton fragment discovered is about 2.5 ft long and 1.8 ft wide. This means that the creature that molted must have been around 8.5 ft (2.6 meters) long and weighed around 110 pounds (50 kg).

However, nobody is yet to find a complete and large, individual Arthropleura fossil. This is because the body armor of these large arthropods fell apart after the creature’s death. Therefore, individual segments are found separately as fossils.

All fossils discovered are believed to be molting shells of the organism, not the actual carcasses. And, in some cases where the carcasses were reportedly found, it is usually incomplete. Researchers have had to make educated guesses about the life of the organism.

Extinction– When Did It Die Out

The Arthropleura existed between 345 to 290 million years ago. The extinction of the Arthropleura occurred a few years after the end of the Carboniferous period, due to the Carboniferous rainforest collapse.

Terrestrial animal life was greatly established during the Carboniferous period. The tetrapods which had originated during the preceding Devonian period became more diversified during this period.

The Carboniferous rainforest collapse was caused by climate change. It was characterized by glaciations, low sea levels, and mountain slides.

The Carboniferous period ended when the moist climate started drying out and rainforest moisture started reducing, followed by the desertification that ushered in the Permian period.

Studies show that the high oxygen level was responsible for the survival of the Arthropleura and its enormous size.

However, other researchers suggested that the lack of competition for resources was responsible for their survival. The lack of known predators must have contributed as well.

The initial hypothesis was widely accepted because it proved valid and tallied with the cause of their extinction. The Carboniferous rainforest collapse and atmospheric oxygen level reduction caused by climate change brought the 8 ft giant to extinction.

Similar Animals to the Arthropleura

The Arthropleura was the largest arthropod to exist, about 345 to 290 million years ago. It co-existed with some other arthropods like pulmonoscorpius and Meganeura.

• Pulmonoscorpius: Pulmonoscorpius is Latin for pulmonis, which means lung and in Greek, skorpios, which means Scorpion. It is also an extinct species that lived in the Carboniferous period about a 336 to 326 million years ago. This was during the Visean and Serpukhovian ages. It preyed on small tetrapods and smaller arthropods, but it wasn’t a threat to the Arthropleuras.
• Meganeura: This is an extinct genus of insects from the late Carboniferous period. They are related to modern-day dragonflies, and were carnivorous.

Conclusion

The living successors of the Arthropleura, such as millipedes and centipedes, have evolved into smaller sizes. This is a result of lesser amounts of oxygen available, which is about 21% today.