How birds out-survived mass extinction that wiped out dinosaurs
Pecking at seeds may have helped ancestors of modern birds survive after the mass extinction event that wiped out dinosaurs 66-million-years ago, a new study suggests.
When the dinosaurs became extinct, may small bird-like dinosaurs disappeared along with giants like Tyrannosaurus and Triceratops. Why only some of them survived to become modern-day birds remains a mystery.
Researchers suggest that abrupt ecological changes following a meteor impact may have been more detrimental to carnivorous bird-like dinosaurs, and early modern birds with toothless beaks were able to survive on seeds when other food sources declined.
"The small bird-like dinosaurs in the Cretaceous, the maniraptoran dinosaurs, are not a well-understood group," said Derek Larson, a palaeontologist at the Philip J Currie Dinosaur Museum in Canada.
"They're some of the closest relatives to modern birds, and at the end of the Cretaceous, many went extinct, including the toothed birds - but modern crown-group birds managed to survive the extinction," said Larson, who is also a PhD candidate at the University of Toronto.
The researchers began by studying whether the extinction at the end of the Cretaceous was an abrupt event or a progressive decline simply capped off by the meteor impact.The fossil record holds evidence to support both scenarios, depending on which dinosaurs are being examined.
Delving into the bird-like dinosaurs, Larson collected data describing 3,104 fossilised teeth from four different maniraptoran families.Researchers were looking for patterns of diversity in the teeth, which spanned 18 million years.The data indicated a rich and stable ecosystem over millions of years and suggested that these bird-like dinosaurs were abruptly killed off by an event at the end of the Cretaceous period.
The team suspected that diet might have played a part in the survival of the lineage that produced today's birds, and they used dietary information and previously published group relationships from modern-day birds to infer what their ancestors might have eaten.Researchers hypothesised that the last common ancestor of today's birds was a toothless seed eater with a beak.
Coupled with the tooth data indicating an abrupt Cretaceous extinction, they suggest that a number of the lineages giving rise to today's birds were those able to survive on seeds after the meteor impact.The strike would have affected sun-dependent leaf and fruit production in plants, but hardy seeds could have been a food source until other options became available again.
The study was published in the journal Current Biology.