Scientists reckon they've found the remains of the smallest meat-eating dinosaur ever to live in North America.
Hesperonychus elizabethae were about the size of chickens, and it's thought they were chasing bugs and tiny animals for food around 75 million years ago.
Even though they were small, they weren pretty fearsome. Scientists say they ran around on two legs, had razor sharp teeth and very sharp claws.
Experts used to think the smallest meat-eaters were the size of a wolf.
The skeletons were actually found back in 1982, but no-one looked at them properly until 2007.
HESPERONYCHUS ELIZABETHAE FACTS
Their claws were the same size as a Canadian quarter (coin)
They were 50cm tall
They weighed around 2kg
It ran on two legs
For a while the scientists thought they came from young dinosaurs, but were surprised when they realised they were fully grown.
Are there smaller ones?
One of the scientists involved, paleontologist Nick Longrich, from the University of Calgary, said: "Its discovery just emphasises how little we actually know, and it raises the possibility that there are even smaller ones out there."
He added: "It turns out that they were here and they played a more important role in the ecosystem than we realized.
"So for the past 100 years, we've completely overlooked a major part of North America's dinosaur community."