In "Jurassic World," Tyrannosaurus rex is no longer the alpha dinosaur. That title belongs to Indominus rex, a custom-designed killer with bigger teeth, longer arms and a nastier attitude.
When the movie hits theaters on Friday, crowds will see plenty of Indominus chasing down Chris Pratt ("Guardians of the Galaxy") and Bryce Dallas Howard ("Spider-Man 3"), who have to deal with the aftermath of a living theme-park attraction gone wrong.
If you think that creating a brand-new dinosaur would be fun ... well, then you would be right. But it also took some restraint.
"It's funny how often we had to pull away from dragon," Colin Trevorrow, director of "Jurassic World," told NBC News.
Sorry, "Game of Thrones" fans, Indominus doesn't breathe fire or carry blond warrior queens on its back. Trevorrow wanted his creation to look somewhat like a real dinosaur. To make that happen, he consulted with paleontologist Jack Horner before the film, along with the film's model builders.
Fans of the original "Jurassic Park" might recognize Horner as the inspiration for Dr. Alan Grant, played in the 1993 film by Sam Neill. He has served as scientific adviser for all of the "Jurassic Park" movies.
He nixed a few early ideas that were thrown around, like making the dinosaur bulletproof. But he surprised Trevorrow by giving the director carte blanche to add any attributes he wanted. If anything, Horner was hoping that the film would go even further than it did.
"I wanted something that looked really different," Horner, sitting below a T. rex skeleton inside of the Natural History Museum of Los Angeles, told NBC News.
The dinosaur does have some wild traits pulled from creatures like tree frogs and cuttlefish — although describing them in detail might spoil parts of the movie. They started with a long list of characteristics and then narrowed them down.
"These kind of things were often decided by the needs of the narrative," Trevorrow said. "If it was going to pick up a guy and bite his head off, it was going to need thumbs."
Indominus is a terrifying monster (sponsored, in the movie, by Verizon Wireless), but compared to the T. Rex, it's not a complete fantasy.
"That is the most plausible part of the movie, making transgenic animals," Horner said, referring to animals with other genes inserted their own. "That is more plausible than bringing a dinosaur back from amber."
Making a brand-new animal with the genes from lots of different animals is more realistic than making an exact copy of a dinosaur that actually existed, he said, mostly because we don't have any dinosaur DNA.
(The "dinosaur blood" recently discovered in poorly preserved fossils might shed new insight on the creatures, but it didn't contain any actual DNA.)
Tweaking current animal genes might be the answer to creating a real "Jurassic World." Horner's attempt to create a "chickenosaurus" is an example of how that might work.
He told NBC News that his team is about 50 percent finished when it comes to modifying a chicken embryo to give it dinosaur-like features. The snout and teeth have been figured out, but the arms and tail — the latter of which involves the tricky task of adding vertabrae — are still a problem.
For now, audiences will have to settle for computer-generated hybrids. There was almost a second one in the movie: a Stegosaurus-Triceratops mix that was cut out of the script right before filming, but not before it became "Jurassic World" merchandise.
"It's fun, because Hasbro basically made a toy that is just for me," Trevorrow said. "I get to have the Stegoceratops that I have always wanted since I was a kid."
Horner enjoyed the movie. He isn't swayed, however, that a real-life "Jurassic World" or dinosaur hybrids would necessarily be bad things.
"You have to remember, we do this all the time," he said. "Do you know what a chihuahua is? It's a genetically modified wolf."
Genetic engineering is essentially super-fast, very specific breeding. If it's used to create fantastic creatures, that is just fine with Horner.
"Breeding is the same thing that we are hypothesizing in 'Jurassic World,'" he said. "I say, we should try to make any kind of animal that we can make."