The catastrophe that spelt doom for dinosaurs may have come close to wiping out birds as well, according to a new study.
A statistical analysis of fossils that date from before and after the mass extinction event, 65 million years ago, suggested it marked an abrupt break in the avian evolutionary family tree.
In fact, Gareth Dyke, lecturer in zoology at University College Dublin, said there was no fossil evidence of a single pre-catastrophe species surviving into post-catastrophe times.
This is in part due to the fragility of bird bones, which makes the fossil record poor. Dr Dyke said it was principally because a huge proportion of ancient bird species - relatives of dinosaurs - perished in the mass extinction, thought to have been triggered by an asteroid or comet striking Earth.
The theory, first proposed by Alan Fedducia in 1995, is that all birdlife today - from hummingbirds to penguins - descended from a very small number of survivors that made it through the hard times following the catastrophe.
Many other animals fell victim to the event, including dinosaurs and marine reptiles, while many species of mammal persisted.
Dr Dyke found further evidence in the fossil of a bird that died shortly before the asteroid struck. Remains of this unnamed species, which resembled a cormorant with tiny teeth, were dug up in a Belgian quarry two years ago.
He said it was the youngest pre-catastrophe bird fossil yet found and appeared to be a member of the genus ichthyornis, none of which survived the impact.
The fossil record shows that within 5 million years after the catastrophe, a host of new bird species had evolved from the yet-to-be identified survivors.
All of these modern birds are distinct from those predecessors dug up to date.
The study will be presented at the annual meeting of the Society of Vertebrate Paleontology in Oklahoma, US, next week.