Scientists have confirmed that the asteroid that killed the dinosaurs claimed another victim — ancient birds also died on that fiery day.
A new study by Yale geology and geophysics postdoctoral associate Nicholas Longrich suggests that the massive asteroid strike that wiped out dinosaurs 65 million years ago was also responsible for the deaths of many bird species. Longrich’s paper, published this week in the journal Proceedings of the National Academy of Sciences, asserts that the many thousands of bird species that exist today evolved from the few dozen that survived the event. Experts in the field said the findings shed light on more than just the history of birds: They expand understanding of extinction events for a wide range of species.
“The [asteroid] extinction hit a much wider range of things that people think it did,” Longrich said. “I think [with further research] we’ll see many things getting completely hammered by this extinction. It’s like hitting a reset button on the ecosystem.”
With colleagues Daniel Field GRD ’12 and Tim Tokaryk, curator of paleontology at the Royal Saskatchewan Museum, Longrich investigated two dozen fossil samples from Yale’s Peabody Museum of Natural History, the American Museum of Natural History, the University of California Museum of Paleontology and the Royal Saskatchewan Museum. Together, these samples represent a large cross-section of avian species alive up to 300,000 years before their extinction, Longrich said. The team observed that archaic bird specimens vanished from the fossil record around the same time as the dinosaurs. They were then gradually replaced by more modern species. Longrich said this simultaneous disappearance proves almost all bird species were wiped out by the asteroid.
Longrich began to look into the subject of archaic birds after researching Canadian fossils from the late Cretaceous Period, he said. He noticed during his studies that during the geological period known as the Cretaceous-Tertiary (K-T) Divide — the time between the asteroid impact and the re-emergence of complex ecosystems — ancient bird species disappeared completely, with modern species later replacing them. This discovery seemed to run counter to the widely held idea that modern birds evolved from a wide range of archaic species, he said.
Field, a co-author of the paper, said the study’s findings debunk a belief held by many researchers that bird species continued evolving, unaffected by the extinction.
“A big open science question in the community right now is, ‘What happened to birds across the K-T boundary?’” Field said. “Some say birds diversified during the K-T boundary, some say after. We have shown that a diverse array of modern birds could not have survived there, proving that modern birds may have diversified afterwards.”
The discovery gives scientists a foundation from which to examine the fossil record at the end of the Cretaceous Period, Tokaryk said, which makes it a landmark discovery for the field.
Indeed, paleontologists interviewed said they are excited by Longrich’s findings.
Lawrence Witmer, a professor of anatomy and paleontology at Ohio University, said Longrich’s research is important not just for the understanding of archaic birds, but for understanding the nature of extinction itself.
“One of the mysteries of extinction pertains to who gets through and why,” he said. “In some cases it appears to be random, but in others there may be features and attributes of species that allows them to survive. What we need to have is a pretty good catalogue of ‘winners and losers,’ and this study does a very good job of sorting through that.”
Longrich’s next project will be to examine the extinction history of lizards and other reptiles across the K-T boundary, he said.
The asteroid that caused the extinction of both birds and dinosaurs, which struck the Yucatan Peninsula over 65 million years ago and caused a dust cloud to obscure the sun for decades or centuries, is thought to have been at least 6 miles wide.