My latest novel SCORPIUS REX is packed with rampaging nine-foot prehistoric scorpions. But these voracious monsters aren’t something I plucked from my imagination. A few million years ago, they were alive and kicking—part of nature’s pantheon of horrifying prehistoric creatures. These monsters make dinosaurs look like kittens in comparison. So, here’s a rundown of my personal favorites, with something for every phobia.

Our list kicks off three hundred million years ago, during the Carboniferous Period—a sixty-million-year stretch when the animal kingdom was seemingly designed by angry fourteen-year-old boys. Let the nightmares begin!

Gaekelopterus Rhenaniae — Modern scorpions represent evolution at its most malicious, combining speed, venom and savage claws into a single creature. Now picture a nine-foot-long version and you’ve got Gaekelopterus. Technically it was a Eurypterid, or sea scorpion, but the ‘sea’ part of that is deceptive. This killer preferred lurking in shallow fresh water, like ponds or marshes … or your swimming pool. This apex predator’s arsenal included acute vision and flesh-shredding pincers the size of your head.

Plumonoscorpius Kirktonensis — Think staying out of the water will save you? Well, think again. Plumonoscorpius was the direct inspiration for the monsters in Scorpius Rex. This land-based prehistoric scorpion only grew about two feet in length, but that’s still three times larger than any modern scorpion. Thanks to its excellent vision it was equally adept at hunting day or night. Though its claws were smaller than its sea scorpion cousins’, don’t let that fool you. The rule of thumb with scorpions is that smaller claws equals more potent venom. That means this lightning-fast predator could sting you with its paralyzing venom then let you watch powerlessly as it ripped you into bite-sized chunks. At a respectable, but still limber two feet this welterweight was big enough to kill you yet small enough to hide under your bed. Have you checked down there lately?

Euphoberia — The Carboniferous Period’s final entry is this three-foot long, venomous centipede. If modern centipedes make your flesh crawl, picture one three times larger and thick as your forearm. Its diminutive modern cousins can routinely hunt birds and bats, so just imagine what prey this beast could take down.

These probably aren’t the only monsters from that bygone era, or even the scariest. Insects and arachnids’ exoskeletons fall apart quickly and therefore aren’t ideally suited to fossilization. So, while science has uncovered these three prehistoric nightmares, it’s possible that a whole catalog of Carboniferous-era terrors have been lost to the sands of time.

Titanomyra — This next entry is a comparative youngster at only fifty-six million years old. It once resided in peaceful Sweetwater Wyoming, population 48,000, but it could have reduced that number to zero in mere days. You see, Titanomyrma means Titan-Ant, a name these six-legged monsters certainly earned. This super-sized ancestor of the fearsome African Driver Ant measured about two inches long—twice the length of any modern ant. Not scary enough? Try multiplying that size by a thousand hungry members of its colony and you’ll start to get the grim picture. Titan colonies would go on raiding marches, shredding and consuming everything in their path, plant and animal alike. Like their tiny ancestors, the African Driver Ant, Titan Ants weren’t venomous—they didn’t need to be. If a modern driver ant latches on to you it can take a pair of pliers to remove it. Titan Ants were just as tenacious but had pincers three to four times larger, with greater biting power to tear into your flesh. Not painful enough for you? Well, these critters also sprayed formic acid as a defense mechanism. So, imagine that bone-deep bite with liquid drain cleaner injected into it.

Wallace’s Giant Bee — Once thought to be extinct, this mega bee not only sports a massive stinger but has a pair of gripping mandibles. It uses those mandibles to scrape resin from trees, or, assumedly, to latch on to you while you scream for God. This rarest of insects exists solely in remote sections of Indonesia. How deadly is its sting? Nobody knows because there aren’t any reported attacks from this relatively gentle giant. Best to keep it that way, since its stinger is about the length of a finishing nail.

Josephoartigasia Monesi — If mega insects and arachnids didn’t scare you, how about a one-ton rat the size of a bull? Technically Josephoartigasia Monesi is an ancestor of the South American pacarana, but let’s be blunt—it’s a giant rat with a stubby tail. This mega Mickey Mouse thrived between two and four million years ago, living alongside apex predators like saber-toothed cats and terror birds. The secret to Josephoartigasia’s survival was its foot-long incisors that carried a biting force three times stronger than a modern tiger. Fortunately, these bad-ass rodents were vegetarians who only used their teeth for self-defense and gnawing on trees.

Tenerife Giant Rat—While not as humungous as the previous rodent, the Tenerife Giant Rat makes up for it in the flesh-crawlingly creepy department. This resident of the Canary Islands was similar to a modern rat, except it was nearly four feet long with powerful back legs designed for digging, climbing, or leaping onto your back in the dark. The Tenerife Giant Rat is a perfect example of Island Gigantism, an evolutionary phenomenon that historically favors rodents. These rats remained the island’s dominant species until about 1000 BC, when the first humans arrived on the Canary Islands. These human invaders brought along something these massive but lazy rats had never encountered—feral cats. This cat invasion quickly led to the giant rats’ extinction and history’s first outbreak of feline obesity.

Titanoboa — Some people think bigger is better, so we’ll wrap it up with a bit of high octane nightmare fuel. This ancestor of the modern boa constrictor dominated the animal kingdom sixty million years ago. Estimated at between forty-two and fifty feet long it dwarfs its largest modern cousins. Weighing over a ton, the thick-bodied Titanoboa likely preferred staying in the water to absorb its massive bulk. But on land or water, Titanoboa was the earth’s apex predator, feeding on prehistoric pigs, lizards and even crocodiles by crushing them in its serpentine coils before swallowing them whole.

So there you go, insects, rats and snakes—the trifecta of human fears. But remember, the best way to overcome your fears is by facing them. So go to Amazon, search for Scorpius Rex by yours truly and add it to your cart. That’ll show those giant monsters who’s boss.

Thanks for reading and don’t forget to check under the bed—because half of this real-life bestiary could be hiding under there. Pleasant dreams.