Bird from the age of dinosaurs deepens extinction mystery

Mystery surrounding the ancestry of modern birds has deepened after the discovery of a rare fossil dating back to the age of the dinosaurs.

Scientists analysed the almost perfectly intact fossil skeleton of a bird the size of a turkey vulture that lived 75 million years ago.

They discovered that the creature, Mirarce eatoni, must have been an expert flyer, just as well adapted for flight as modern birds.

Yet this bird and other members of its family group, the enantiornithines, all vanished in the mass extinction that wiped out the dinosaurs  around 65 million years ago.

Only one group of birds, whose descendants are still living today, survived the cataclysm that followed a massive meteor impact off the coast of Mexico.

Why this should be the case has been an on-going mystery. The advanced traits seen in M. eatoni creates even more of a puzzle.

US researcher Jessie Atterholt, from the University of California at Berkeley, said: “We know that birds in the early Cretaceous, about 115 to 130 million years ago, were capable of flight but probably not as well adapted for it as modern birds.

“What this new fossil shows is that enantiornithines, though totally separate from modern birds, evolved some of the same adaptations for highly refined, advanced flight styles.”

Despite having the appearance of a modern bird, M. eatoni probably had teeth in the front of its beak and claws on its wings as well as its feet, said the scientists.

The fossil, housed at the University of California Museum of Palaeontology at Berkeley, was discovered in Utah in 1992 but has only now undergone analysis. The findings are published in the journal PeerJ.

All birds evolved from feathered two-legged “theropod” dinosaurs, the large group of meat-eaters that included Tyrannosaurus rex.

Enantiornithines were “very, very common” and could be found all over the world, said PhD student Ms Atterholt.

M. eatoni had a deeply keeled breast bone, implying large and powerful flight muscles.

It also had anchor points known as “quill knobs” on its forearm bones. In modern birds quill knobs help to strengthen the wing feathers for active flight.

“This is the first discovery of quill knobs in any enantiornithine bird, which tells us that it was a very strong flyer,” said Ms Atterholt.

A possible reason for the extinction of enantiornithines is that they were mostly forest dwellers, according to the researchers.

Many experts believe the meteor strike that ended the dinosaurs’ reign sparked a global fire storm that destroyed much of the world’s forests.

The name Mirarce combines the Latin word for wonderful with the mythical Greek character Arce, the winged messenger of the Titans.