Some dinosaurs were equipped with night vision that enabled them to hunt at night, according to a study published Friday in the journal Science.

Researchers at the University of California, Davis, in the United States were able to make these judgments by studying the eye area of fossilized dinosaurs and compared them with those of existing birds and reptiles.

The results suggest that small, meat-eating dinosaurs were nocturnal; large, plant-eating dinosaurs tended to forage both during the day and at night.

Velociraptors, the type featured in the movie "Jurassic Park," were likely night-stalkers.

There was no finding on Tyrannosaurus rex, because there are no fossils with sufficiently well-preserved scleral rings, the university said in a statement.

Plant-eating dinosaurs could see a fair bit at night, because they likely had to eat round the clock to keep their bellies satisfied, while flying dinosaurs, like birds, were active only during the day, said the study.

The study counters the widely held belief that most dinosaurs hunted by day while smaller mammals roamed at night.

"It was a surprise, but it makes sense," said co-author Ryosuke Motani, professor of geology at UC Davis.