When viewers tune in to Fox's "Terra Nova" time-travel TV series, premiering tonight on Fox, they'll see an 85 million-year-old world that's pretty much "terra incognita" for dinosaur experts. And that's just fine with world-famous paleontologist Jack Horner.

"I suggested 85 million, because it's a time that we know the least about, and it's kind of in the middle of the Cretaceous period, which means we could bring some older dinosaurs forward and take some younger dinosaurs back without getting in too much trouble," Horner told me.

So even though the long-necked, plant-eating dinosaur known as Brachiosaurus died out long before Tyrannosaurus rex came onto the scene, their cousins can mix it up in the computer-generated landscape created for "Terra Nova."

"We just cannot use a T. rex, but there are tyrannosaurs, so we can certainly create an animal that looks very similar to T. rex," Horner said.

Tonight's premiere raises the curtain on a series that some critics have characterized as a cross between "The Lost World" and "Lost," with a flashy "Stargate" time portal and an extra dash of "Swiss Family Robinson" thrown in. There are family dramas, shadowy conspiracies and seemingly indecipherable rock markings to stir the pot, but the success of the mega-expensive series arguably depends on the dinosaurs — just as it did for the "Jurassic Park" movie series.

Horner is familiar with the terrain — not only because of his roles as curator of paleontology at Montana's Museum of the Rockies, professor at Montana State University and one of the world's foremost fossil-hunters, but also because he was a consultant for "Jurassic Park" and a model for the movie's alpha-scientist character.

Steven Spielberg, co-executive producer for "Terra Nova," was the one who brought in Horner as a consultant for the "Jurassic Park" movies. "I guess he liked what I did there, so [the TV show's producers] called and asked if I could do it" for "Terra Nova" as well, Horner recalled.

Horner works with the artists and the writers on the dino concepts. "My job really is to make sure the dinosaurs are as accurate as they can be, even if we invent them," he said. "If they're going to be raptorlike dinosaurs, they have to have the characteristics of a raptorial dinosaur ... but when it comes to headgear, we can do a lot of things."

Slasher movie
That last comment relates to the first dinosaur invented for the series: a nasty critter referred to as the "Acceraptor" and nicknamed the "Slasher."

"He's got some characteristics that are new, but still within the realm of possibility," Horner said. "The only detail I can tell you is, it's going to be a scary dinosaur. Let's put it this way: I wouldn't want to be in the forest with a Slasher, especially at night."

Further details have seeped out through the dinosaur blogs: The Slasher sports some gaudy headgear that Brian Switek, who blogs about paleontology for Smithsonian magazine and Wired, has criticized as a "horribly lame" look (see below for more). It has some fearsome-looking claws, but its deadliest weapons are the sharp barbs that whip around at the end of its yards-long tail. "As far as I know, that's totally made up," Bob Strauss, who manages About.com's guide to dinosaurs, told me.

Horner said he's willing to give the writers and artists wide latitude when it comes to dreaming up dinosaurs. "If we know something for sure, then we'll keep it within the bounds of science," but if there are blank spaces in the scientific picture, a little (or a lot of) imagination is allowed. This is Hollywood, after all.

"Just like the people in the movie, the dinosaurs are actors. They will go faster than we think dinosaurs can go," Horner admitted.

Food for thought for dino fans
That was the case for "Jurassic Park," and Horner is hoping that "Terra Nova" will offer even greater dramatic possibilities, for the dinosaurs as well as for the human actors.

"It's one thing to make a movie. Movies are two hours of a single story," Horner said. "The really cool thing about 'Terra Nova' is that it is a series, so we have the capability of building and building and building on it, each time seeing new animal and plant characters and still being able to follow the family that the story is about. In many ways, it's a lot better than a movie, just on a smaller screen."

And if dinosaur fans want to argue over the finer points of the dinosaur depictions, that's just fine with Horner, too. "If people are watching and paying attention like that, that would be great," he told me.

Here are some of the reviews from experts who are paying attention:

• University of Maryland paleontologist Thomas Holtz, who wrote the official "Jurassic Park" dinosaur guide and has consulted on many dinosaur documentaries, including the Discovery Channel's "Dinosaur Revolution":

The main reason why the "Terra Nova" colonists go through a rupture in space-time is because the world has become an environmental wasteland by the year 2149. People have to wear "re-breathers" on their faces to cope with the polluted air. But Holtz noted that the world of 85 million B.C. wasn't exactly a breath of fresh air, either.

"If you're trying to escape climate change by going back to the past, you wouldn't want to go back to 85 million years ago, where CO2 is almost 1,000 parts per million, as opposed to 392 at present," he observed. Holtz acknowledged, however, that an elevated carbon dioxide level isn't the only environmental problem facing the smoggy, run-down world of 2149.

As for the dinosaurs, Holtz had a couple of pieces of advice for the writers. First, don't get too specific about the dinosaur names. Instead of referring to Brachiosaurus (the long-necked plant-eater that makes an early appearance on tonight's show) or Carnotaurus (the toothy, horned dinosaur that almost runs down Terra Nova's patriarch in the episode), use more generic names (brachiosaurs or abelisaurs, respectively). There's no evidence that either Brachiosaurus or Carnotaurus was around 85 million years ago, but it's plausible to claim that their distant cousins were.

"Saying it more generically is safer," Holtz said.

Also, as the series goes on, Holtz hopes the writers get the locale right. For example, no Carnotaurus fossils have been found in North America, so if the series claims that the "Terra Nova" colonists are settling in Cretaceous Chicago, coming upon Carnotaurus' older cousins there would be "as unlikely as encountering a koala in Montana," Holtz said.

Most of the TV audience might not care that much about the terminology, but it's better to have the dino-geeks for you than against you. "They get mad enough with the dinosaur documentaries," said Holtz, speaking from experience.

• Science writer Brian Switek, author of Smithsonian's Dinosaur Tracking blog and the book "Written in Stone: Evolution, the Fossil Record and Our Place in Nature." Here's Switek's pithy email critique of the "Terra Nova" dinos:

"All I have seen of the 'slasher' is the promotional artwork, but, yes, I'm sorry to say that the creature design for the dinosaur is horribly lame. The poor creature looks as if the special effects artists took one of the Jurassic Park raptors, stuck a crest from an oviraptorid dinosaur on its head, and then gave it a bad toupee. So many fantastic and terrifying dinosaurs have been found — dromaeosaurs with double sickle-claws (Balaur), Allosaurus-cousins with sail backs (Concavenator), crocodile-snouted hunters (Baryonyx), and others — that the I think the show's creators would have done better to draw inspiration from actual dinosaurs rather than trying to dress up a Deinonychus.

"Then there's the scientific issue. Thanks to multiple discoveries of feathered dinosaurs during the past 15 years, we know beyond a shadow of a doubt that many coelurosaurs — the group to which raptors, tyrannosaurs, oviraptorids and others belong — were at least partly covered in feathers. Even Velociraptor arm bones have been found with quill knobs for the attachment of feathers! (The significance of this is that we can now detect the presence of feathers on some dinosaurs even if the feathers themselves are not preserved.) Therefore, the 'slasher' should be a feathery beast and look less like a dinosaur with a comb-over. Every year more feathered coelurosaurs are found, and it's time that television shows and movies featuring these dinosaurs restore the animals with their full plumage. ...

"It is true that our knowledge of dinosaur life around 85 million years ago (the beginning of the Santonian age) is relatively limited. Compared to what we know about the later Campanian (83 million to 70 million years ago) and Maastrichtian (70 million to 65 million years ago) ages, the world of dinosaurs during the Santonian is still fuzzy and waiting to be fleshed out by new discoveries. That said, I don't have a problem with a show creating new dinosaurs or even bringing in dinosaurs from slightly older or younger time periods. (If I recall correctly, Carnotaurus — a Campanian dinosaur from prehistoric Argentina — is in the show.) Sometimes scientific accuracy needs to be bent a little to make compelling television. That's just the way it goes when you want to tell a story.

"Nevertheless, I don't think any imaginary dinosaur can really compare to the real animals we're finding. Spielberg and the show's co-creators can dream up as many dinosaurs as they want, but, to me, speculative creatures like the slasher are always going to pale in comparison to the bizarre array of wonderful dinosaurs paleontologists have uncovered."

Science writer Bob Strauss, dinosaur guide for About.com, who saw an advance screening of "Terra Nova" and discusses it in a review:

Strauss said "Jurassic Park" stirred up a lot of controversy on the subject of dinosaur verisimilitude. For example, real Velociraptors were nowhere near smart enough or agile enough to turn a doorknob, and pterosaurs weren't strong enough to carry off a kid.

"Terra Nova" could well do the same, and not just because of slasher's barb-whipping tail. Did brachiosaurs really eat small lizards, or were they strictly herbivores? Shouldn't the TV series' Carnotaurus have arms as wimpy as the real thing? Where's the slasher's hind-foot claw?

But judging by the first show, Strauss thinks dino-geeks will stick with the series, if for no other reason than to get their weekly Cretaceous fix and debate how the Hollywood monsters compare with the real things. "They're just so happy to have dinosaurs on TV," he told me.

More about dinosaurs in fact and fiction:

• 'Dinochicken' scheme puts evolution in reverse
• Fox sees family, not sci-fi, at heart of 'Terra Nova'
• Spielberg: 'Jurassic Park 4' coming in a few years
• Search for Cretaceous dinosaurs on msnbc.com 

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