Chinese scientists unearth ancient underwater scorpion that was the size of a corgi

A handout photo. Chinese scientists unearthed an ancient sea scorpion that was about the size of a medium-sized dog.
PHOTO: South China Morning Post

Imagine heading out for a snorkelling trip and coming upon a one-metre-long scorpion, tail extended over its head, pouncing on its preys and then lifting them with its large forearms to gobble them up.

If you lived in China hundreds of millions of years ago , this would not have been out of the realm of possibility, and it certainly would have been disconcerting because you would have been running into the apex predator of the era.

Chinese scientists unearthed this sea scorpion, called Terropterus xiushanensis, according to a research paper published in the latest issue of Science Bulletin.

An artistic rendition of Terropterus xiushanensis, a one-metre-long sea scorpion that prowled the seas of what is now China hundreds of millions of years ago.
PHOTO: Yang Dinghua

The ocean beast was about the size of a small corgi and probably lived in the oceans of the southern half of modern-day China during the Silurian Period, which was between 416 million and 443 million years ago.

The scientists did not lock down a specific time frame when they believed the Terropterus lived.

The scorpion’s most striking feature was the sharp barbs extending from its forearms, which the authors of the study hypothesised were used to catch prey.

“Bearing such large spiny legs and probably a poisonous telson to catch and strike the prey, Terropterus is likely to have played an important role of top predators in the marine ecosystem during the Early Silurian when there were no large vertebrate competitors in South China,” the authors wrote in the study.

The fact that the forearms, called pedipalps, are used for hunting is an interesting evolutionary nugget because, in many arachnids, especially spiders, they are often used for reproduction. But, among arachnids, scorpions are a notable exception of pedipalps being used as predatory tools.

Photos of the sea scorpion fossils as well as a sketch of what scientists think it looked like.
PHOTO: ScienceDirect

The “poisonous telson” is reminiscent of modern scorpions, albeit it lacks the notable venom gland, according to artist renditions of the Terropterus.

While Terropterus was an apex predator during its time, it would be unlikely to pose much of a threat to humans if it existed today, preferring instead to feast on molluscs and fish.

The sea creature was a mixopterid, which were part of a group of extinct arthropods called eurypterids and were closely related to horseshoe crabs and modern arachnids, such as spiders and scorpions.

During the Silurian Period, Eurypterids, like our Terropterus , were the apex predators. The arthropods of this time were huge, with the largest known species being the Jaekelopterus rhenaniae , which is believed to have grown as large as 2.5 metres.

The Terropterus is the oldest known mixopterid in China and is thought to have lived around Gondwana, a supercontinent that formed around 600 million years ago and broke up approximately 180 million years ago.

An image shows where the Terropterus probably lived, and what its arms looked liked.
PHOTO: ScienceDirect

Two island-like formations off the coast of Gondwana eventually drifted together to form modern-day northern and southern China.

“The palaeogeographical distribution of mixopterids was rather limited until now and no examples of this group have been previously discovered in Gondwana,” the scientists wrote.

The paper is based on two separate sets of fossils, one from near Wuhan, in central China’s Hunan province, and the other from Xiushan, in southwest China’s Chongqing province.

The Silurian Period was part of the Paleozoic Era, a time of incredible evolutionary change. It was defined by shallow oceans, which allowed sunlight to penetrate and allowed for diverse ecosystems to flourish.

This article was first published in South China Morning Post.