The toothless beaks of the ancestors of modern-day birds may explain why they were able to survive the likely mass-extinction event that wiped out the dinosaurs.
This idea comes from a team of palaeontologists from the University of Toronto, Canada – they used data from over 3,100 fossilised dinosaur teeth to investigate both the pace of extinction and why birds were able to outlive their close relatives. The study was published today in Current Biology.
“We propose that the ability of modern bird ancestors to eat seeds was a key feature of their survival through the extinction event,” lead researcher Derek Larson told SBS Science. “We examined the tooth fossil record of these small bird-like dinosaurs because the skeletal remains of small dinosaurs are very rarely preserved.”
Dinos died suddenly
Just like in sharks, dinosaur teeth were continuously replaced throughout the life of the animal and their enamel coating gave them the strength to be fossilised. As a result, fossilised teeth provide the most comprehensive information about bird-like dinosaurs.
To get a gist of how diverse the dinosaur species were, the researchers carefully tracked the shape variation of the fossil teeth over the last 18 million years of the Cretaceous Period.
Their findings indicate that instead of a long-term decline of dinosaurs prior to extinction, as has been argued by many based on the fossil record, the prehistoric giants were wiped out by a sudden and catastrophic event – most likely by an asteroid impact.
“If the dinosaurs were experiencing gradual decline before the extinction, this should show up in their teeth as a decrease in disparity,” says study co-author Caleb Brown.
“Conversely, if the dinosaurs were doing just fine before a sudden extinction, we should expect the disparity of the teeth to be constant.”
“Our results suggest that the latter is true, indicating that, at least for the small meat-eating dinosaurs, their role in the ecosystem was stable and extinction was sudden.”
Cracking bird seed
Data collected from the fossil teeth also revealed that the ancestors of modern-day birds, with their toothless beaks, were able to outlive their dinosaurs because of their seed-based diet.
"Following the asteroid impact, many of the Earth’s ecosystems may have collapsed, but seeds would have been a stable and reliable source of food,” says Brown.
Professor John Long, a palaeontologist from Flinders University, says the research is innovative, and provides a logical explanation for the dinosaur conundrum.
“It implies feeding on seeds was the main trait that enabled small-sized birds to survive the extinction event, but not other small bird-like dinosaurs with serrated teeth or larger dinosaurs,” Long told SBS Science.
However, Long thinks the study may cause controversy as it presents the opposite conclusion to another study released earlier this week that suggested dinosaurs had been in decline for tens of millions of years before extinction.