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In Alberta's dinosaur-rich Badlands, bigger has always been better.

But new research suggests a “collecting bias”, which historically favoured the recovery of massive predators such as the Tryannosaurus rex, caused paleontologists to overlook tiny dinosaurs, including one partially-covered with feathers that dined on meat and insects and was smaller than a cat.

The discovery of Hesperonychus elizabethae a slender, pint-sized carnivorous dinosaur with dagger-like teeth, was published on Monday in the Proceedings of the National Academy of Sciences.

Believed to be the smallest dinosaur species ever found in North America, this research is also being hailed as an important step in fully understanding what the continent's ecosystem looked like more than 75-million years ago.

“There's got to be other things out there like this. If we could have overlooked this for so long, there is a very good chance we are overlooking other things,” said Nick Longrich, a University of Calgary paleontologist, who co-authored the study with Philip Currie, a renowned University of Alberta paleontologist. “You see what you are looking for.”

Their research concluded that the delay in identifying Hesperonychus, which means “western claw,” was partly due to a “collecting bias that has favoured the recovery of large, relatively complete dinosaur skeletons.”

Mr. Longrich said he had long suspected that mini-dinosaurs likely roamed North America after small adult dinosaurs were discovered in China and Mongolia in recent years.

That hunch and lots of luck were on his side when he was rummaging around drawers storing a 25-year-old fossil collection at the University of Alberta in 2007.

He soon found a well-preserved piece of hip bone that eventually led to the discovery of Hesperonychus. The bones had been recovered in 1982 in southeastern Alberta but never studied.

“People collect stuff faster than they can be studied...so there is a big backlog of work ready to be done,” Mr. Longrich said.

He suspects that the Hesperonychus was likely quite common because lots of little claws and other fossils have been recovered over the years in Alberta but never fully investigated.

Up until this discovery, the smallest carnivorous dinosaur ever recovered in North America was the size of a wolf.

The Hesperonychus, which weighed about two kilograms and stood about 50 centimetres tall, had sharp claws, including an enlarged sickle-shaped claw on its second toe and feathers behind its arms and legs. It closely resembled a smaller version of its cousin, the bipedal predator Velociraptor.

The slender, pint-sized creature, which roamed the earth at the end of the Cretaceous period, ate everything from baby dinosaurs to insects.

Mr. Currie said the discovery of Hesperonychus represents the start of new research opportunities for paleontologists in Alberta, a hotbed of dinosaur activity for the past 100 years.

“When we first started working with dinosaurs in Alberta, everybody came here to collect big specimens because they are good display specimens,” he said.

However, Mr. Currie said those results gave researchers and the public “a very skewed understanding of the old ecosystem, where just about everything is big.”

He said this new research offers a “much more balanced view that looks more like modern ecosystems.”