12 most dangerous dinosaurs of all time, ranked by a paleontologist

• Dinosaurs have fascinated humans for centuries, even though they never overlapped with humankind.

• Still, we know enough about their characteristics to imagine living together.

• A paleontologist helped Insider rank which dinosaurs would have been the most dangerous to us.

Humans and dinosaurs never lived at the same time. But what if they did? Which would be the dinosaurs you should be most afraid of?

Paleontologists have been studying dinosaur remains for decades, uncovering the incredible ways they developed to protect themselves and attack others.

Based on these characteristics, paleontologist Cassius Morrison helped Insider rank which would be the biggest threat to humanity.

Here are the most dangerous dinosaurs and what could have made them a threat, according to Morrison.

11: Iguanodon

This dinosaur was a herbivore, but it had fierce tools to defend itself.

"It has like a really big thumb spike like a knife, used to defend against carnivores," said Morrison.

Morrison is pursuing a PhD in vertebrate paleontology from University College London and the Natural History Museum London.

At about nine feet tall and 30 feet long, unlike some bigger dinosaurs, it would have cared if it felt threatened by a human. But it generally is thought to have been quite gentle, landing it further down in the list.

"Because it's a herbivore, it would only do it in self-defense. So that's why it's at 11," said Morrison.

Iguanodon was the first dinosaur to be discovered and has been studied since then. "It's quite a famous and important dinosaur," said Morrison.

10: Ankylosaurus

Also a herbivore, Ankylosaurus could be quite fierce.

"These are the ones with heavy armor, like a heavy tank," said Morrison, ranking it 10th.

The stout dinosaur, standing at about 5.5 feet at the shoulder, was so heavily armored that "even its eyelids had armor on it," said Morrison.

But the fearsome part of the dinosaur would be its massive hammer-like tail.

"If the tail was to whack you, you'd be gone," he said.

"But again, it's unlikely to attack a human if you are just being careful and walking around."

9: Sauropods

These long-necked animals — a type of dinosaur rather than one species — come at number nine. Here, it's not a scary claw or a weapon that makes them fearful — it's their sheer size.

"These are massive like Brachiosaurus, Diplodocus, Argentinasaurus," said Morrison.

"They are the biggest animals ever to walk the earth."

These animals could kill you just by stepping on you. Or even by stepping near you. A study found that turtles, dinosaurs, and crocodiles drowned in the footprint left behind by a sauropod walking through marshy ground, Morrison said.

"The sauropods walked a swampy marshy environment, really churned up the soil, and they made that sort of quicksand with their footprints," said Morrison.

But it's not only their legs you should be careful of. In his book, Emory paleontologist Anthony J. Martin, with the help of physicist Jed Brody, calculated that the speed and weight of Diplodocus vomit falling from the height of its head would be enough to kill a dinosaur.

By extension this would also kill a human, said Morrison.

8: Triceratops

Triceratops is the last herbivore on Morrison's list. These horned animals may have been particularly spooked by humans sniffing around their young.

It's important to remember the difference in scale when it comes to dinosaurs. Just like a butterfly wouldn't fill us with dread, a small human would probably go practically unnoticed to some of the bigger dinosaurs.

But a human standing up would line up nicely with the eye of a Triceratops standing around 10 feet tall.

"Because a human would probably be in their field of vision, not like a little mouse or rat, they're probably more likely to charge if they thought you were a threat," said Morrison.

It'd be difficult to outrun them as they probably could hit 20 to 25 mph, per Morrison.

"I think if you were to get too close, they could probably charge you down or use their horns to impale you like a rhino or a buffalo," he said.

7: Gigantosaurus

Gigantosaurus, "the big bad" in the "Jurassic World: Dominion" movie as Morrison called it, is the biggest land-dwelling carnivore of all time with a length of around 45 feet and a height of around 12 feet.

"But they often hunted the bigger sauropods. So the reason why it's quite low down is it might just see a human as not being worth the effort," said Morrison.

6: Spinosaurus