A long period ago before the evolution of sharks and barracudas, some deadliest predators used to roam around primordial seas. Sea scorpion aka Slimonia acuminata was the member of eurypterid family, used to thrive around 430 million years ago. This ancient sea monster was the ancestor of modern scorpions and horseshoe crabs.
Seeker reported that some of the sea scorpions were more than 10 feet long and their main weapon was sharp pinching claws and serrated tail spine. A research team from the University of Alberta has described that sea scorpions used to dine on early fish species and their long serrated tail spine helped them to dominate their prey.
Biological Science Professor of theUniversity of Alberta and lead author Scott Persons said,“Slimonia would have lurked in the shallow waters of lagoons and lakes along the coast of primordial Europe, during the Silurian Period (443.7–416 million years ago). At the time, our vertebrate ancestors were primitive fish”. Persons and his team have collected the sea scorpion fossil remains from the Patrick Burn Formation near Lesmahagow, Scotland.
According to Mail Online, this sea scorpion was not more than one and a half feet long so it couldn’t be considered as the largest eurypterids, but It's weaponized tail was more advanced than the other predators of that time. Modern lobsters and shrimps flip their tails vertically to swim, but their ancestors wave their tail horizontally as their tails were vertically inflexible.
Persons explained, this feature allowed sea scorpions to slap and slash sideways aggressively, meeting a little hydraulic resistance that keeps them steady on the target. That time another top ocean predator was cephalopods, ancestor of modern giant squids, octopi, and cuttlefishes. However, it is very difficult to calculate the full body size and shape of cephalopods, because their soft bodies were very difficult to fossilize.
