All  
A fossil of Parioscorpio venator, a 437-million-year-old scorpion that resembles modern species. Source: Wendruff et al., Scientific Reports, 2020

This Scorpion Was Among the First Lifeforms to Walk on Earth

Print

Almost half a billion years ago Earth was largely inhabited by armored arthropods with segmented bodies and jointed limbs, shelled mollusks, and wobbly unrecognizable fishlike organisms darting about. What all these species had common, besides hunting for prey at sea, was that all these creatures breathed not with lungs, but with gills. Now, experts have found the remains of an ancient scorpion which they say might be among the very first animals to have set foot on land.

During the Silurian geologic period from 443 million to 416 million years ago, a creature with strong limbs and the ability to draw oxygen from air crawled ashore and much later that creature’s decedents would be us. The identity of that innovative creature, however, is always being updated as the scientific method and its tools of exploration and testing advance. Now, make way for the ‘latest’ contender being presented as being among ‘the very first animals to have set foot on land.’

Ancient Mutations in the Scorpion’s Breathing Apparatus

The findings are presented in a paper published in the  journal Scientific Reports , which details its 1980s discovery in a Wisconsin quarry, north of state highway 164. Named, Parioscorpio venator, meaning ‘ancestral scorpion and hunter,’ this ancient predator measures 2.5 centimeters (0.98 inches) in length and is thought to have lived about 437 million years ago.

According a report in The Smithsonian Magazine , this new discovery and dating pushes the date of the earliest known scorpion back by up to three million years. But what’s more, the fossil is the ‘earliest evidence’ of any creature with breathing apparatus capable of coping on land, the scientists wrote in their paper.

Two fossil specimens of Parioscorpio venator, unearthed in Wisconsin. Scale bars are 5 millimeters. (Wendruff et al., Scientific Reports, 2020)

Two fossil specimens of Parioscorpio venator, unearthed in Wisconsin. Scale bars are 5 millimeters. ( Wendruff et al., Scientific Reports, 2020 )

An article in The Guardian explains that ‘earliest arachnid’ yet discovered had, like modern scorpions, ‘two large claws and a tail with a sting at its end.’ The earliest animals, however, were all aquatic but scorpions are known to have been among the first groups of animals to have become fully land-dwelling, and these two new fossils add to a growing debate about when animals made the shift, say the scientists.

But the team of researchers behind the discovery say it was the scorpion s ‘internal structure’ that most excited them.

Internal Refit and Enhancements

Dr. Andrew J Wendruff, a paleontologist at Otterbein University, Ohio, and co-author of the research said in the paper that the fossil was found in a shallow water setting and probably lived in the sea and on land. What enabled the creature to do this was its ‘pulmo-pericardial sinuses;’ and the creatures respiratory structure indicated to the scientists that it was indeed able to live on land. In modern scorpions, pulmo-pericardial sinuses connect the animal’s respiratory organs with its circulatory system, and the ancient animal was, according to Dr. Wendruff, like modern scorpions, able to breathe air.

A fossil of Parioscorpio venator (a) compared to a microscope image of Centruroides exilicauda (b) and Hadogenes troglodytes (c), both modern scorpions. "bl" stands for book lungs, a respiratory structure, and "pc" stands for pericardium, a structure that encloses the heart. Scale bars are 1 millimeter for a and b and 1 centimeter for c. (Wendruff et al., Scientific Reports, 2020)

A fossil of Parioscorpio venator (a) compared to a microscope image of Centruroides exilicauda (b) and Hadogenes troglodytes (c), both modern scorpions. "bl" stands for book lungs, a respiratory structure, and "pc" stands for pericardium, a structure that encloses the heart. Scale bars are 1 millimeter for a and b and 1 centimeter for c. ( Wendruff et al., Scientific Reports, 2020 )

Whats more, the ancient scorpion fossil represents ‘the earliest evidence’ of any animal doing this and the scientists say scorpions have changed little in almost ‘440 million years.’ Like humans, animals aspire to resource rich environments which have not yet been exploited and Dr. Wendruff said land was ‘barren by today’s standards,’ and that a move to terra firma would have ‘offered advantages.’

May the Oldest Land Lubber Please Stand Up?

Even though I earlier described the creature’s ‘pulmo-pericardial sinuses connecting the animal s respiratory organs with its circulatory system,’ nowhere did I say anything about lungs. And regarding this point Dr. Wendruff ‘urged caution’ because the fossilized scorpion ‘did not show’ whether it had lungs or gills. He wrote, lungs or gills would be 'the key character’ and so long as these are missing I think we have to ‘be cautious’ about concluding whether or not it lived on land, he said.

Reconstruction of Parioscorpio venator gen. et sp. nov. Structures outlined in grey are inferred based on Proscorpius osborni. Structures highlighted with grey infilling are the preserved elements of the pulmonary-cardiovascular system. (Wendruff et al., Scientific Reports, 2020)

Reconstruction of Parioscorpio venator gen. et sp. nov. Structures outlined in grey are inferred based on Proscorpius osborni. Structures highlighted with grey infilling are the preserved elements of the pulmonary-cardiovascular system. ( Wendruff et al., Scientific Reports, 2020 )

While the scorpion represents the ‘earliest animal’ to have emerged from the seas onto land, when it got there it was far from alone, as an intelligent life form had long since established itself as the king of dry land.

A 2016 study by Dr. Martin Smith, a paleontologist at Durham University, published in the  Botanical Journal of the Linnean Society , demonstrated how fossilized fungi, called Tortotubus, lived about ‘440 million years ago’ and were about 5 million years younger than the previous oldest fossil.

A leading filament of T. protuberans with primary branches and nascent secondary branches. (verisimilus/CC BY 3.0)

A leading filament of T. protuberans with primary branches and nascent secondary branches. (verisimilus/ CC BY 3.0 )

According to The Washington Post , this study showed ‘fungi’ were the oldest fossilized ‘land-living organisms’ ever discovered, but now, in this newly discovered scorpion’s respiratory structure, and knowing it was able to live on land about 437 million-years-ago, Dr. Andrew J Wendruff and his team at Otterbein University in Ohio have closed the gap between the previous oldest fossil and the emergence of fungi by a cool 3 million years.

Top Image: A fossil of Parioscorpio venator, a 437-million-year-old scorpion that resembles modern species. Source: Wendruff et al., Scientific Reports, 2020

By Ashley Cowie

Next article