We see fossil reconstructions or illustrations of species that have come and gone and we sometimes say, “Come on now, that can’t be real!” Or maybe you don’t, but I have, because these creatures look like they came from a horror film or a child’s most frightening nightmares.

1. The Creature: Platybelodon
The Nightmare: Pink Elephants on Parade on Acid

Quick -how many prehistoric relatives of the elephant can you name? Mammoth, mastodon, and …that’s it, right? Meet Platybelodon. Even the minds who conceived Heffalumps and Snuffleupagus would consider this creature to be too ridiculous to believe. When I first encountered Platybelodon in this illustration by DeviantART member Sk00tie, I thought the artist had made up the species. But no…

Platybelodon was a “shovel tusker”. Ten million years ago, it roamed Africa, Europe, Asia, and North America, eating trees and plants that grow in swamps. It is one of several ancient elephants from the Gomphothere family. See more of Platybelodon in a YouTube video.

2. The Creature: Bullockornis
The Nightmare: The Demon Duck of Doom

What looks a bit like a duck, but is eight feet tall and eats wombats? Bullockornis planei was a bird that roamed Australia as far back as 15 million years ago, but possibly also survived to see mankind.

A giant skull found a few years ago led scientists to believe Bullockornis was omnivorous, and devoured other animals whole. This bird earned the nickname the Demon Duck of Doom.

3. The Creature: Opabinia
The Nightmare: Nunu with Five Eyes

Opabinia regalis flourished 500 million years ago during the Cambrian period. This odd creature had five eyes, two of them on stalks, and a proboscis resembling a vacuum cleaner hose that made up about a third of its body length. Just think of the Teletubbies’ Nunu with extra eyeballs! Fossil specimens are pretty small -shorter than your finger- but there is speculation that these were juveniles and the creature may have grown bigger. Opabinia is a creature that so far defies classification. Should it be labeled an arthropod or an annelid, related to crustaceans or trilobites? It may be an ancient ancestor of them all. Illustration by Nobu Tamura.

4. The Creature: Quetzalcoatlus
The Nightmare: Flying Dragon Wants to Eat You

Quetzalcoatlus northropi may have been the largest flying animal ever. The estimated wingspan gleaned from fossil evidence is 36 feet, although earlier extrapolations put it as high as 60 feet. Either way, that’s a big animal. It took a lot of muscle power to get 500 pounds off the ground! This pterosaur lived about 65 million years ago. Quetzalcoatlus northropi ate dinosaurs for breakfast, which is enough to fuel anyone’s nightmares. Illustration by Mark Witton and Darren Naish.

5. The Creature: Titanoboa
The Nightmare: Big Snake

The name Titanoboa means “big snake.” The species Titanoboa cerrejonensis is the biggest snake ever discovered, which was about four years ago in Colombia. The fossil remains of a couple of dozen such snakes were studied, leading scientists to estimate their size at a maximum 15 meters, or 50 feet! Titanoboa cerrejonensis was a constrictor that lived around 60 million years ago, eating animals the size of crocodiles -whole. Illustration by Jason Bourque.

6. The Creature: Dunkleosteus
The Nighmare: Jaws with Armor

You might have seen this scary fish, if you had been around 400 million years ago. Dunkleosteus was an armored fish that grew to be twenty feet long and had sharp teeth in massive jaws that could slice through bones. Scientists have been divided on how to classify Dunkleosteus among fish, since evidence discovered at different times links it to different types of existing species.

DeviantART member DNK-Anais gives us this illustration of how terrifying Dunkleosteus would seem to other sea creatures and any land animal that got too close.

7. The Creature: Procoptodon
The Nightmare: A Hairy Grinch with Claws

Procoptodon goliah was a giant short-faced kangaroo. It was about twice the weight of the modern red kangaroo (but not much taller), and hopped around on feet that had one toe each! It ate only plants, and could stretch to reach branches 12 feet above ground. This kangaroo had eyes that faced forward, which gave it the ability to see depth and a resemblance to the Grinch from the Dr. Seuss book. There were also smaller species of Procoptodon, which were all extinct by 40,000 years ago.

8. The Creature: Pristerognathus
The Nightmare: What’s Behind the “Beware of Dog” Sign

The genus Pristerognathus were animals that lived 250 million years ago in Africa. They are Therocephalians, which are reptiles that have mammalian characteristics. One of the few things we know about Pristerognathus is that it was carnivorous and had a huge head compared to the rest of its body, and most of that head was jaws and teeth. However, the whole animal was about the size of a house cat. Illustration by Dmitri Bogdanov.

See also: The Bigger They Are: 10 Ice Age Giants