Seed diet helped birds live while the dinosaurs died

When the object that created the Chicxulub impact struck the Earth and wiped out nearly all of the dinosaurs approximately 66 million years ago, some avian-like species somehow managed to survive and gave rise to modern-day birds. How they did so has long been a mystery.

Now, new research published Thursday in the journal Current Biology has discovered why these specific creatures were able to avoid extinction: it’s all due to the fact that they happened to have toothless beaks and dined on seeds, which could still be found in the aftermath of the impact and the “nuclear winter” that followed, according to BBC News and UPI reports.

The ecological changes that resulted from the impact, lead author Derek Larson, a paleontologist at the Philip J. Currie Dinosaur Museum in Alberta, and his colleagues explained, appear to have been more detrimental to carnivorous bird-like dinosaurs than plant eaters, and those without any teeth were able to survive on seeds when other sources of food became increasingly scarce.

“After this meteor, you’re left with essentially a nuclear winter where really not much is growing, the plants aren’t able to grow to provide nourishment for plant-eaters and then meat-eaters aren’t able to access plant-eaters if they’ve all perished,” he explained to BBC News. “We think that the survival of birds had something to do with the presence of their beak.”

Inability to utilize alternate food source doomed some maniraptorans

Larson, who is also a Ph. D. candidate at the University of Toronto, and his fellow investigators analyzed more than 3,000 fossilized teeth from a group of small, bird-like dinosaurs that lived in the Cretaceous period and were known as maniraptorans. Maniraptorans were among the closest relatives to modern birds, he explained, but many wound up going extinct.

“Modern crown-group birds managed to survive the extinction,” he said Thursday in a statement. “The question is, why did that difference occur when these groups were so similar?” To learn the answer, Larson and his colleagues analyzed the teeth hoping to determine whether the patterns of variation remained consistent over time, or if they became more uniform as time passed.

If the variation increased, they explains, it would suggest that changes to the environment were responsible for a long-term species loss. However, if the team maintained their differences over time, it would suggest that the ecosystem remained stable and that these bird-like dinosaurs had been abruptly killed off at the end of the Cretaceous, likely due to the Chicxulub impact.

Ultimately, they found that maniraptoran dinosaurs “maintained a very steady level of variation through the last 18 million years of the Cretaceous,” said Larson “There were bird-like dinosaurs with teeth up until the end of the Cretaceous, where they all died off very abruptly. Some groups of beaked birds may have been able to survive the extinction event because they were able to eat seeds,” while those unable to use this alternate food source simply died out completely.

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Image credit:  Danielle Dufault

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