Researchers at University of Alberta have discovered a dinosaur fossil in New Mexico that indicates they were alive about 700,000 years after the mass extinction.
Larry Heaman and colleagues found the bone of a hadrosaur as being only 64.8 million years old. The common notion is that a mass extinction of the dinosaurs happened between 65.5 and 66 million years ago.
Heaman and colleagues used a new direct-dating method called uranium dating, wherein a laser beam unseats minute particles of the fossil, which then undergo isotopic analysis.
The uranium atoms in bone decay spontaneously to lead over time and once fossilization is complete the uranium-lead clock starts ticking. The isotopic composition of lead therefore, determines the absolute age of the animal.
Experts believe that debris from a giant meteorite impact blocked out the Sun, causing extreme climate conditions and killing vegetation worldwide.
Heaman and his research colleagues have several theories as to why the New Mexico hadrosaur came from a line of dinosaurs that survived the great mass extinction events of the late Cretaceous period (KT extinction event).
One is that in some areas the vegetation wasn''t wiped out and a number of the hadrosaur species survived. The researchers also say the potential survival of dinosaur eggs during extreme climatic conditions needs to be explored.
If the team’s uranium-lead dating technique bears out on more fossil samples then the KT extinction paradigm and the end of the dinosaurs will have to be revised.