Palaeontology: Sea scorpions were the prehistoric predators - Triops Galaxy

Palaeontology: Giant sea scorpions were the prehistoric predators

In 2021, researchers presented the discovery of a partial impression of Arthropleura. The fossil of a gigantic millipede, which was discovered in northern England 326 million years ago, measures 76 centimetres and shows 25 body segments without a head. Experts estimate that this indicates a potential body length of up to 2.6 metres. However, these calculations are uncertain as the head of this creature has never been found. It is thought that Arthropleura may have been just under two metres long. In comparison, the largest sea scorpions reached a length of over 2.5 metres. There were doubts that these gigantic arthropods were the main hunters of the seas.

T. rex of the sea of this time

If this assumption is correct, another monster could have been the dominant creature on land: Jaekelopterus rhenaniae, a member of the sea scorpions (eurypterids) that lived 467 to 253 million years ago and are only distantly related to modern scorpions. These giants also reached a length of 2.6 metres and were more closely related to the swordtails that still exist today, known as arrow-tailed crabs.

Studies suggest that their claws were too fragile to hunt large, well-armoured prey. Their eyesight was also not considered sufficient for top predators, which jeopardised their position at the top of the food chain.

At one point, Jaekelopterus and similar species were considered apex predators due to their massive pincers. However, some palaeontological studies in recent years suggest that these large eurypterids may not have been efficient hunters.

However, more recent findings now contradict this assumption: Palaeontologist Simon Braddy from the University of Bristol used analyses of fossils, computer modelling and experiments with robotic eurypterids to come to the conclusion that smaller sea scorpions such as Acutiramus tended to specialise in crustaceans as prey, while the giants Pterygotus and Jaekelopterus successfully hunted well-armoured fish from the Placodermata group. These giant eurypterids could therefore be regarded as the T. rex of the sea at this time. According to Braddy, corresponding traces on the carapaces of fish fossils and fossil eurypterid faeces would confirm this thesis.

Influence on the early development of vertebrates

The study, published in the journal Bulletin of Geosciences, also confirms a long-held assumption: in the past, some palaeontologists had assumed that sea scorpions could have influenced the early evolution of vertebrates, especially fish, by triggering a veritable race between predators and their prey.

Braddy argues that the eurypterids’ pincers were mainly used to catch and hold prey. The actual killing and dismemberment was done with their more powerful mouthparts. Experiments also suggest that the large sea scorpions swam more slowly than previously assumed, as their relatively small paddles did not provide enough propulsion in the water. It is therefore possible that they lay in ambush for their prey.

Previous studies had largely rejected this idea, but Braddy’s research suggests that pterygotids and other eurypterids did indeed have an impact on the early evolution of vertebrates.

Sladjan Lazic

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