Fossil Teeth Show That Seed-Eating Birds Could Survive Dinosaur Extinction

Many of the smaller bird-like dinosaurs too became extinct 66 million years ago, though why some dinosaurs remain behind is not known.

Ecological changes after the meteoric impact affected carnivorous bird-like dinosaurs. However, just the early modern birds with toothless beaks remained unharmed, as they have managed to survive only by eating seeds.

"The small bird-like dinosaurs in the Cretaceous, the maniraptoran dinosaurs, are not a well-understood group," said Derek Larson, a Ph.D. candidate at the University of Toronto and first author on the study. "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. The question is: why did that difference occur when these groups were so similar?"

Studying the extinction at the end of the Cretaceous period, Larson and his team tried to find out if it was a slower or an abrupt decline. Fossil records disclose support from both theories.

Studying 3,104 fossilized teeth from various maniraptoran families showed diversity in the teeth, which included the shape and size. With fewer variations between the teeth over time, the loss in diversity would indicate a decline in the ecosystem as well as a long-term species loss. However, if the variations remained, it would show a "rich, stable ecosystem" along with the abrupt killing of bird-like dinosaurs by the end of the Cretaceous era.

Scientists found support for the second explanation, observing a consistent level of variation over 18 million years of the Cretaceous, and then abrupt extinction.

The team suspects that diet played an important role in survival. Studying the dietary research from earlier to modern-day birds, they located the final ancestor of today's birds, which was a toothless seed-eater with a beak.

The findings show that the lineages eventually evolving into today's birds managed to survive due to the birds' ability to eat seeds after the meteor impact damaged most other sources of food.

"There were bird-like dinosaurs with teeth up until the end of the Cretaceous, where they all died off very abruptly," said Larson. "Some groups of beaked birds may have been able to survive the extinction event because they were able to eat seeds."

The findings were published in the April 21 issue of Current Biology.