400 Million Years Ago, A Giant Scorpion Might Have Been a Crustacean

Extinct giant aquatic arthropods called sea scorpions (Eurypterids) were apex predators. A new study suggests that early species of carcinosomatoids, with their scorpion-like spiny limbs, fed on trilobites, while later species preferred armored fish. Carcinosomatoids evolved into scorpions, but not the giant scorpion-like creatures that lived 400 million years ago. Preactorus and Brontoscorpio which is published in Walking with monsters (TV series) was probably a crustacean.

Sea scorpions (family: Ophiocephalidae) are ancient aquatic creepies (arthropods, meaning they have segmented bodies, exoskeletons, and jointed legs) that lived from 467 million years ago until about 253 million years ago.

Some pterygian Eurypterids can grow to lengths of nearly 2.6 metres, making them the largest insects ever to have lived. Eurypterids also include the predatory carcinosomatoids, namely the megalograpts, carcinosomatoids and mixopterids, which have long spiny limbs and can grow to lengths of up to 2 metres.

Carcinosomatoids used their long, spiny limbs to catch prey and burrow into the mud, and computer models suggest that they were slow swimmers who preferred to live close to the sea floor as ambush predators.

New research on fossils found alongside megalograptids suggests that they were primarily associated with trilobites, a diverse group of extinct marine arthropods.

Carcinosomatids tend to live in symbiosis with lightly armoured phyllocallid crustaceans and lingulid brachiopods (lamp shells).

Mixopterid fishes tend to coexist with more heavily armoured fishes such as therodonts, osteostracans and pteraspids.

Fossilized feces (coprolites) prove that they ate trilobites, armored fish, and even their own kind (cannibals).

The idea that nudibranchs influenced the evolution of armored fishes in the predator-prey arms race is often dismissed.

The study suggests that mixopterids and pterygians had some influence on their evolution (and on our very ancient ancestors).

Megalograptus is interpreted as being more primitive than previously thought, which means that early (Ordovician) crinoid diversity has been overestimated.

Scorpions are thought to have evolved from a Mixopteridae-like ancestor, evolving claws (palps), stingers, and comb-like sensory pecten on their undersides.

Giant scorpions may be the creatures of your nightmares, but they actually existed in Scotland's Carboniferous period. Pulmonoscorpiusand Gigantoscorpio.

Reconstruction PulmonoscorpiusA giant scorpion (70 cm long) from the Carboniferous period of Scotland (330 million years ago). Image by Junnn11 / CC BY-SA 4.0.

Even longer (1 meter) scorpions PreactorusThis dinosaur, which lived in Herefordshire, England, is also thought to have lived 412 million years ago.

However, the grooves on its shell, the pustular ornamentation, and the recurved first segment suggest that it is in fact a crustacean.

Bennett TaltraThey come from the same layer and region and may be related (or slightly smaller) Preactorus.

BrontoscorpioIt is an estimated 86cm long (400 million years old) scorpion featured in a BBC television series. Walking with monstersOnly a small portion of the claws are known, and it is probably a crustacean. Image courtesy of Impossible Pictures.

Brontoscorpio(86cm long), discovered in Worcestershire, England (400 million years ago) and featured in an award-winning BBC television series. Walking with monsters Possibly a crustacean too.

So giant scorpions, along with giant millipedes measuring two metres in length and giant dragonflies with wingspans of 75 centimetres, didn't come into existence until the Carboniferous period 70 million years later.

Modern scorpions gradually acquired their modern characteristics: early scorpions had more primitive legs and eyes, and lacked an anterior mouth cavity for feeding on land, so were probably aquatic or amphibious.

The oldest known scorpion Palioscorpio It was discovered in Wisconsin from the Early Silurian (437 million years ago) but has been reinterpreted as a trilobite-like arthropod.

The oldest scorpion is now Dolichophonus (433-438 Ma) Originating from Scotland.

this the study Published in New Jarlbuch in Geology and Palaeontology.

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Braddy, S.J. 2024. Palaeoecology and phylogeny of carcinosomatid eurypterids: ichnolog- y and palaeoassemblages. New Jarlbuch in Geology and Palaeontology; doi: 10.1127/njgpa/2024/1206