The scariest dinosaur in 'Jurassic World: Dominion' isn't actually a dinosaur

Where's my Dimetrodon hive? It's our damn day.

Though Jurassic World: Dominion may have...been what it is, there's one thing the film absolutely nailed. Almost 30 years since Steven Spielberg's original, the noble Dimetrodon has finally been given its moment in a Jurassic Park film.

We've only ever seen Dimetrodon once in the franchise and it doesn't count, as a mere display version behind glass in Benjamin Lockwood's manor museum in Jurassic World: Fallen Kingdom. Now, the non-dinosaur (we'll get to that) has debuted with one hell of a scene in the third Jurassic World instalment.

In director Colin Trevorrow's film, as Dr. Ellie Sattler (Laura Dern), Dr. Alan Grant (Sam Neill), and Maisie Lockwood (Isabella Sermon) are attempting to escape the Biosyn facility, they find themselves trapped in a cave where multiple Dimetrodons are snoozing. Rudely awoken, the creatures attack them in the dark. It's a major moment for Dimetrodon, face-to-face with the OG cast members — fan favourite Dilophosaurus can't even claim that. Even Dr. Ian Malcolm (Jeff Goldblum) appears in this scene, in a totally useless way, but he's there nonetheless. What's more, the angry Dimetrodon cluster threatens a genuinely high stakes plot point — if Ellie doesn't get out of there with a certain sample, the world is screwed. So happy for them! What a rush!

Super locusts are gonna be the least of your worries, folks. Credit: Universal Studios / Amblin Entertainment

So, Dimetrodon really hasn't been in a Jurassic film before?

It's not the first we've seen of Dimetrodon being related to the Jurassic franchise in general — but never in the films (no, we're not counting the statue). Hell, Dimetrodon's been in Disney's Fantasia but not a Jurassic film.

YouTuber Klayton Fioriti has a spectacularly detailed history of its appearances in Jurassic Park merchandise, toys, trading cards, comic books, and video games, and how Dimetrodon has a history of being benched in the franchise while other dinos enjoy solid onscreen stompery (looking at you, made-up Indominus Rex). Plus, he notes that the creature wasn't included in the books the original two films were based on.

"A case could be made against putting Dimetrodon in a Jurassic film as the animal wasn’t included in either of Michael Crichton’s novels and isn’t in fact a dinosaur at all, scientifically speaking," says Fioriti in the video below. "But this still would make the Permian creature unfairly excluded from getting exposure when creatures like the...Pterosaurs and Sea Beast have made an appearance before it."

What the hell is a Dimetrodon?

I'm so glad you asked. First of all, no, it's not a dinosaur.

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"If I got a cent every time someone claims that Dimetrodon is a dinosaur I would already be a wealthy man," Dr. Hans-Dieter Sues, senior scientist and curator of vertebrate paleontology at the Smithsonian National Museum of Natural History, told Mashable.

"One reason is that Dimetrodon is usually associated along with dinosaurs in children's books and toy packages or even labeled as a dinosaur. The other reason is that people automatically assume that every scary-looking prehistoric beast is a dinosaur. Dimetrodon is, in fact, not even a reptile but an early member of the evolutionary lineage leading to mammals."

The oldest terrestrial apex predator who thrived during the Permian Period (between 299 to 251 million years ago) and millions of years before the arrival of dinosaurs, Dimetrodon is immediately recognizable by the big sail-like fin on its back. The American Museum of Natural History says this "may have been used for temperature regulation, to attract mates, or to frighten off other animals."

Here's the Smithsonian National Museum of Natural History's Dimetrodon grandis fossil, found in 1881 in Baylor County, Texas. It is 100 percent glorious.

Dimetrodon grandis Romer & Price, 1940 Credit: Smithsonian National Museum of Natural History

Dimetrodon grandis Romer & Price, 1940 Credit: Smithsonian Natoinal Museum of Natural History

How accurately is Dimetrodon represented in the film?

Look, this is Jurassic Park, and we all know that from the very first film back in 1993, Steven Spielberg's velociraptors didn't have the muppety feathers they would have had IRL. So, grain of salt, people.

In Jurassic Park: Dominion, we first spy a Dimetrodon by its back sail only, a formidable fin appearing from a foreboding pond. I asked Sues whether or not the animal was a water-dwelling creature or whether this was Hollywood throwing Dimetrodon into the deep end.

"Dimetrodon is very common in sediments laid down upon a vast floodplain in what is now Texas and Oklahoma," he says. "It is commonly found with amphibians and other at least semi-aquatic animals. Thus, I would not be surprised if it had entered ponds and streams in that setting."

So, that scene checks out, but what of the cave attack? Did Dimetrodon ever actually live in such a place, hence why Biosyn would keep them there? "It is very unlikely that Dimetrodon was a habitual cave-dweller," says Sues. "There would have been little if any suitable food in a cave."

In the scene itself, when Ellie, Alan, and Maisie find themselves surrounded by about three of the animals, I wondered if Dimetrodon actually lived in packs like this or whether, like many other predators, it flew solo. "It is quite possible that Dimetrodon would hunt in packs although a fully-grown Dimetrodon would be a top predator on its own," says Sues.

As reported by New Scientist, Sues measured Dimetrodon bones with University of Chicago paleontologist Caroline Abbott, and determined the animal's body structure as most linked to a caiman, and one that moved in a crocodilian manner — which you'll see they reflect in the film. Importantly, this is a carnivore on all fours, living millions and millions of years before major predator dinosaurs like Allosaurus (also in the film) become enormous and ran on two legs. I feel that. Using what you've got to create chaos and front up to Hollywood-played archaeologists is just plain awesome.

Dimetrodon diehards, our sail-backed icon is finally in the Jurassic franchise, making a debut that more than made up for the decades of sitting on the bench. Just like Neill, Dern, and Goldblum, Dimetrodon is a true OG and deserves onscreen respect.

Jurassic World: Dominion hits cinemas June 10. Here's Mashable's review.