[ethereal music] -[Narrator] One hundred and fifty million years ago, in the late Jurassic, there was an undisputed king of Europe.

One of the biggest dinosaurs ever found on the continent, a 35-feet tall, 45-ton giant, Lusotitan.

The challenge for the Walking with Dinosaurs team is, how do you bring this gigantic herbivore to life?

Capturing a colossus like Lusotitan requires a delicate blend of cutting-edge science, creative filmmaking, and elite visual effects.

Oh, and a man on a beach holding a really long pole.

At the VFX studio, our long-extinct Lusotitan is constantly evolving, from initial sketches to relatively basic 3D models, and into increasingly realistic moving dinosaurs.

But out in the field, the film crew is shooting the landscapes that the digital dinosaurs will eventually inhabit.

They've come to this beach in Portugal, following right in the footsteps of where these ancient beasts once roamed.

-[Stephen Cooter] We're here today to film a sequence where two male Lusotitans are fighting over a female.

-[Narrator] Every scene has been meticulously researched and planned.

But on the ground, you still need a healthy dose of imagination.

-[Stephen] One of the challenges is um kind of making sure, with an animal that size, that you've got enough space for it and that it's all in the frame.

You know, these things were, you know, as long as a swimming pool, and I guess it's not a kind of animal on a scale of anything that's alive today, so it's hard to imagine how big they are.

-[Narrator] So, for now, our soon-to-be magnificently visualized dinosaur is just, yeah, that man with the pole from earlier.

-We work to absolute scale of what we would expect the animals to be, and so rather than just sort of shooting some fresh air over there, even though that's just a man holding a pole, eventually this will be a glorious shot of a Lusotitan sort of tilting up to his face, all being well.

-[Narrator] As the fight reaches its climax, one defeated Lusotitan comes crashing down to earth.

[deep, anguished bellow] But the victorious Lusotitan still has one more battle to win for the heart of his mate.

-[Stephen] So, he's won the fight with the male, but now he's got, I guess, a load more work to do because he's got to win over the female, and for dinosaurs like this, we think they may have engaged in a kind of mating ritual, like a dance.

-[Narrator] With the real-life background footage shot, it's now up to the VFX team to truly bring Lusotitan to life.

To visualize a mating scene between two 35-foot giants, the VFX artists are going to need some help.

Luckily, they have some inspiration from the natural world today.

[woman harmonizing] [water splashing] But how would the gigantic neck of a Lusotitan actually move?

Could its neck even support the type of movement required?

Every single decision made by the film and VFX crew is taken only after consulting with the world's top dinosaur scientists.

Paleontologist Pedro Mocho can prove that Lusotitan's neck was much lighter than you might expect.

[soft bellows] And instead of solid bone, Lusotitan could reinforce its mammoth neck with air sacs that burrowed through its neck and backbone.

-[Pedro Mucho] This kind of structure allows them to support more weight, be more dynamic and flexible.

-[Narrator] Flexible enough to dance.

[ground rumbles] But what happens if the Lusotitan's dancing isn't quite sealing the deal?

-[Stephen] So, we've got to the point now where our hero's won the fight with the male, he's been kind of doing a mating dance, but um she's still not kind of buying it.

So, this is where he plays his uh trump card.

-[Narrator] And that trump card is this.

This bizarre spectacle may look impossible, but this too takes its inspiration from dinosaurs' only living descendants, who can certainly be quite flamboyant when trying to impress a mate.

But if nature provides the inspiration, the latest science may back it up.

There could be direct fossil evidence for it in the skull of Lusotitan's closest relative.

-[Pedro] So here we have a cast of a Giraffatitan skull.

-[Narrator] It supports a huge ridge of bone that may have housed a large crest that some think could have flared and bulged just like the most extravagant of modern birds.

-[Pedro] They may have similar functions of some of the crests that we can see in birds.

Exhibition, for mating, it's evolving here for the first time in this group of dinosaurs.

-[Narrator] It's go big, or go home.

And on this occasion, this Lusotitan is not going home alone.

And now, after years of planning, research, and filming, the very latest science and cutting-edge animation come together, finally transforming and bringing these titans to life.