Scorpions have been found in many fossil records, including marine Silurian and estuarine Devonian deposits, coal deposits from the Carboniferous Period and in amber. The oldest known scorpions lived around 430 million years ago in the Silurian period. Though once believed to have lived on the bottom of shallow tropical seas,[ early scorpions are now believed to have been terrestrial and to have washed into marine settings together with plant matter. These first scorpions were believed to have had gills instead of the present forms' book lungs though this has subsequently been refuted. The oldest Gondwanan scorpiones (Gondwanascorpio) comprise the earliest known terrestrial animals from Gondwana. Currently, 111 fossil species of scorpion are known. Unusually for arachnids, there are more species of Palaeozoic scorpion than Mesozoic or Cenozoic ones.

The eurypterids, marine creatures that lived during the Paleozoic era, share several physical traits with scorpions and may be closely related to them. Various species of Eurypterida could grow to be anywhere from 10 centimetres (3.9 in) to 2.5 metres (8.2 ft) in length. However, they exhibit anatomical differences marking them off as a group distinct from their Carboniferous and Recent relatives. Despite this, they are commonly referred to as "sea scorpions". Their legs are thought to have been short, thick, tapering and to have ended in a single strong claw; it appears that they were well-adapted for maintaining a secure hold upon rocks or seaweed against the wash of waves, like the legs of a shore crab. Read more ...

Scientists Identify The World's Biggest Known Scorpion, The Size of a Dog   Science Alert - June 10, 2026

If you were wandering around Earth's floodplains 415 million years ago, you wouldn't have come across any other mammals - but you would have had to be wary of a giant scorpion measuring more than a meter (3.3 feet) in length. After an extensive new fossil study, researchers in the UK have confirmed the identity of Praearcturus gigas, which may be the largest known scorpion in history.

A segmented little beastie that swam Earth's seas nearly half a billion years ago has now been identified as the grandparent of spiders, scorpions, and horseshoe crabs.   Science Alert - May 26, 2024

It's called Setapedites abundantis, a teeny tiny creature around 5 millimeters long, and it thrived in an ocean that once covered what is now Morocco, 478 million years ago.

First microwhip scorpion from Mesozoic period found in Burmese amber   PhysOrg - March 9, 2016

It's smaller than a grain of rice, yellowish, trapped in amber and lived 100 million years ago alongside dinosaurs. Meet Electrokoenenia yaksha, a newly described type of microwhip scorpion, or palpigrade, from Myanmar, whose minute fossilized remains have been found, trapped in Burmese amber.