Forget lions, tigers and bears. Consider, instead, a 10-ton prehistoric predator called a Gorgonosid and venomous spiders the size of a trash-can lid.

Those are just some of the intimidating critters featured in Primeval, a new BBC America series with its eye squarely focused on enticing the sci-fi crowd.

The series has already been running in England for a year, and the conceit is simple: Somewhere in the English countryside, a hole has ripped in the space-time continuum and prehistoric creatures are walking from the past into forests of the present.

When evolutionary zoologist Nick Cutter (Douglas Henshall) is asked to investigate, he does so with a scoffing attitude. This is the stuff of Jurassic Park and he's not buying it.

Besides, he's still preoccupied with the disappearance of his wife Helen years earlier in the same urban forest where the new sightings are being reported.

He's joined in his search for evidence of dinosaurs by his dashing assistant Stephen Hart (James Murray), a nerdy graduate student named Connor (Andrew-Lee Potts), a reptile expert from the London Zoo (Hannah Spearritt) and Claudia Brown (Lucy Brown), a junior agent from the Home Office whose job, should the reports prove true, is to keep it all quiet.

Primeval moves swiftly from enchanting to eerie. A woman is chased across a parking lot at night by something large and ferocious. A 10-year-old boy is searching for his lost pet in the forest when he encounters something terrifying. He escapes back to his house, only to have the creature peer into his bedroom window. A dinosaur invades an elementary school and terrorizes a teacher and student.

There's the obligatory government bureaucrat (Ben Miller) whose job isn't to protect the public from harm, but to protect his own bosses from controversy. He'd just as soon the whole mess went away.

Of course, at heart, Primeval is a science fiction story. What are these tears in space and time that appear in the oddest places?

In the show's second episode, one vortex arises in the subway tunnels. Instead of being a portal to the Jurassic period, it's from 100 million years earlier. Meet a centipede the length of a train car.

The special effects are uniformly solid, though not as impressive as you'd find on the big screen.

Still, credit the producers for not going the obvious route and throwing in a T. Rex. They give us dinosaurs we've likely not seen before, and thus can't predict their behavior.

To complicate matters, Dr. Cutter steps through one of the vortices and finds proof that his wife was there.

Could she still be alive in the ancient past?

We'll know more about that in a few episodes. For starters, Primeval holds a lot of promise.

Perhaps series co-creators Tim Haines and Adrian Hodges put it best when asked what the series is about:

"What would happen if humanity was suddenly confronted with its dark and terrifying past? . . . Would we stand together or fall apart?"

I guess that depends whether we were glued to the telly watching a show like Primeval.

pearsonm@RockyMountainNews.com or 303-954-2592

Primeval

* Grade: B+

* When and where: 7 p.m. today, BBC America (Dish 135, Direct TV 264, Comcast 162)