Massive dog-sized scorpion ruled the sea 400 million years ago

The fossil of a sea scorpion the size of a dog has been discovered by researchers in south China.

The team who found it believe that the fossil is between 443 million and 419 million years old!

Called Terropterus xiushanensis, it was a type of arachnid, related to animals like the horseshoe crab.

At one metre in length, the sea scorpion was 16 times longer than the scorpions we know today.

The horseshoe crab, pictured here, is a relation of the ancient sea-scorpion

The Terropterus xiushanensis used its long arms with spikes to help capture food as it roamed the sea bed.

It would have had poison in its tail to help overpower its prey.

Sea scorpions are known as Mixopteridae, and have a large skeleton outside their body, strong front legs and a curved spine.

The study of the fossil was carried out by researcher Wang Han and Professor Wang Bo of the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences.

"Our knowledge of mixopterids is limited to only four species in two genera, which were all based on a few fossil specimens from the Silurian Laurussia 80 years ago," the researchers explained in their study.

It's hoped that this fossil will help the scientists find out more about its species, as it is the first of its kind discovered in 80 years!