Silurian scorpion

The Silurian Scorpion was a species of giant scorpion (arachnid) from the Silurian period, which hid under the sand and tracked prey by sensing vibrations.

Characteristics
Silurian Scorpions were large arachnids which possessed a purple and sandy-brown exoskeleton. They closely resembled whip scorpions; with spiked claws, six legs, antennae-like frontal sensory organs, and a whip-like flagellum tail at the end of the pygidium. The Scorpions varied in size; from approximately three feet tall and eight feet long, (Episode 12 Sea Scorpions) to twenty-five feet long and twelve feet tall. (Episode 12 Sea Scorpions)

Silurian Scorpions were also sand burrowers, able to dig into and burrow under sand and easily move around with speed under the sand. From what was seen, Silurian Scorpions preferred to stay in the sand, tracking prey on the surface by the vibrations they make on the sand surface. Usually, once a Scorpion under the sand homed in on the prey, such as a Silurian Millipede, that's the source of the vibrations, it would come up under it and drag it down under the sand to be eaten; though a Scorpion would sometimes instead just come up onto the surface to chase down and eat the prey. (Episode 12 Sea Scorpions)

Silurian Scorpions seemed to have loose social structure; while multiple Scorpions would attack and pursue a common target together, when one Scorpion had caught a live meal, the Scorpions would sometimes aggressively fight over the food.

Trivia

 * The Silurian Scorpion closely resembles the Whip Scorpion also known as the Vinegaroon.
 * The concept of scorpions dragging victims under the sand by sensing vibrations and preferring to stay in the sand is similar to the Graboids in Tremors.
 * Similarly, both the Graboids and the Silurian Scorpions were initially mistaken for snake creatures by the people who encountered them (the Graboids due to their long, prehensile tongues, and the Scorpions due to their long, curling tails).
 * The Silurian Scorpions' attack strategy may be a reference to Scorponok from the 2007 Transformers movie.

Errors

 * Scorpions as big as Silurian Scorpions wouldn't have been able to breathe properly in the Silurian and would have been crushed by gravity. A major lack of plants in the Silurian also leads to a small amount of oxygen in the atmosphere. An arthropod's lungs need a higher amount of oxygen the bigger the creature grows. To get to the size of the Silurian Scorpion, the air would need to be at least 30-40% oxygen. The desert had simple land plants but there were no land animals. Though the Silurian is known for giant scorpions which did exist, these scorpions only in the sea and were only nine feet long, such as Pterygotus and Brontoscorpio; although they were known to have came out of water, but only for a limited time.