The current generation of birds is said to be the evolutionary successor of the birdlike dinosaurs, but the succession was nearly not to be. A new study has pointed that despite the mass extinction of dinosaurs, seeds have helped the birds to survive the extinction.

Most birdlike dinosaur species lived during dinosaurs died off during the mass extinction event that occurred roughly 66 million years ago. Several early bird species, however, survived. Why did these close relatives of feathered dinosaurs outlast their predecessors?

To answer that question, scientists first needed to understand the decline of maniraptoran dinosaurs at the end of the Cretaceous period.

To determine whether these creatures were already in decline or were killed off abruptly, a team of scientists led by paleontologist Derek Larson analyzed 3,104 fossilized teeth from four different maniraptoran families. The fossil comprised a time span of 18 million years.

Consistent variation among the teeth fossils suggest the species enjoyed rich genetic and physiological diversity right up until the end.

“The maniraptoran dinosaurs maintained a very steady level of variation through the last 18 million years of the Cretaceous,” Larson, a doctoral candidate at the University of Toronto, said in a news release. “They abruptly became extinct just at the boundary.”

The latest research was published in the journal Current Biology.