Meryl Streep and Sandra Bullock share actress award

Voters for the Critics' Choice Awards could not pick an outright best actress winner, so split the prize between Meryl Streep and Sandra Bullock.

Streep, a winner for Julie and Julia, and Bullock, who won for The Blind Side, both attended the Los Angeles ceremony to collect their awards.

Iraq war drama The Hurt Locker picked up the best film award, with Kathryn Bigelow also winning for best director.

Avatar won five prizes, including best action movie and technical awards.

Directed by James Cameron, the ex-husband of Bigelow, the film was honoured for its cinematography, editing, art direction, sound and visual effects.

The best actor award went to Jeff Bridges for country music film Crazy Heart.

The best supporting actor and actress awards were collected by Christoph Waltz for Inglourious Basterds and Mo'Nique for Precious respectively.

Quentin Tarantino's World War II epic Inglourious also won best original screenplay and ensemble cast, which included Brad Pitt, Eli Roth and Michael Fassbender.

Musical movie Nine, starring Penelope Cruz, Kate Hudson and Nicole Kidman, failed to win in any of the 10 categories in which it was nominated.

Bullock, who on Friday donated $1m (£614,798) to aid the medical charity Doctors Without Borders' relief effort in Haiti, used her time on the winners' podium to talk about the disaster.

"We're all so lucky to be here tonight when so many others are in pain," she said.

"I hope we can all send good love and thoughts and whatever we can."

Last year, voters for the Critics' Choice Awards plumped for Slumdog Millionaire as best film, paving the way for the British hit to sweep the Oscars, where it won eight awards on the night.

Alligators and birds share lung structure and ancestor

Alligators and birds share a breathing mechanism which may have helped their ancestors dominate Earth more than 200 million years ago, scientists say.

Research published in the journal Science found that like birds, in alligators air flows in one direction.

Birds' lung structure allows them to breathe when flying in low oxygen, or hypoxic, conditions.

This breathing may have helped a common ancestor of birds and alligators thrive in the hypoxic period of the Triassic.

Mammals 'hiding'

"It might explain a mystery that has been around for quite some time", Dr Colleen Farmer from the University of Utah told BBC News.

The mystery in question is why the archosaurs came to dominate Earth after the planet's worst mass extinction 251 million years ago.

Archosaurs evolved into two different branches which developed into crocodilians, dinosaurs, flying pterosaurs and eventually birds.

Synapsids, which evolved to include mammals, had been dominant in the Permian period before the mass extinction.

Some survived but were toppled from their perch by the archosaurs.

Any mammal-like synapsid survivors "were teeny liittle things hiding in cracks" said Dr Farmer. "I think it's because they couldn't compete.

"It wasn't until the die-off of the large dinosaurs 65 million years ago that mammals made a comeback and started occupying body sizes larger than an opossum."

To demonstrate alligator lung mechanisms, the scientists measured airflow in anesthetised animals, showing it flows in one direction rather than in and out of chambers.

They also pumped water containing tiny fluorescent beads into the lungs of dead alligators to observe the flow.

Puzzle solved

The researchers believe the similarity in lung structure may explain why some animals were better able to adapt after the extinction, when oxygen levels dropped.

"We know that birds are really good at breathing in hypoxic conditions. They can fly at altitudes that would kill a mammal," said Dr Farmer.

"Many archosaurs, such as pterosaurs, apparently were capable of sustaining vigorous exercise. Lung design may have played a key role in this capacity.

"That's been a puzzle, why do birds have these very different lungs? But now we can date it back to the common ancestor of birds and crocodilians.

"It implies that all dinosaurs, herbivores like Triceratops and carnivores like Tyrannosaurus, had bird-like lungs," Dr Farmer added.