Canadian researchers say a fossil found in New Mexico contradicts a long-held belief that dinosaurs went extinct abruptly 65.5 million to 66 million years ago.

University of Alberta scientists determined an unearthed femur bone of a hadrosaur is only 64.8 million years old, indicating the plant-eating dinosaur was alive at least 700,000 years after the mass extinction event many paleontologists have said wiped all non-avian dinosaurs off the face of earth forever, a university release reported Thursday.

It's long been accepted a mass extinction of the dinosaurs happened between 65.5 million and 66 million years ago, most likely when a giant meteorite impact threw material into the atmosphere that blocked out the sun, causing extreme climate conditions and killing vegetation worldwide.

UA professor Larry Hearman says there could be several reasons why the New Mexico hadrosaur line of dinosaurs survived the mass extinction event. It's possible that in some areas the vegetation wasn't wiped out and a number of the hadrosaur species survived, Hearman says, and not enough is known about the potential survival of dinosaur eggs during extreme climatic conditions.

Hearman says if more fossil samples provide the same dating results then the extinction paradigm and the end of the dinosaurs may have to be revised.