The 150-million-year-old Archaeopteryx fossil has had its crown as 'first known bird' reaffirmed by the publication of a new evolutionary tree.

In a study published today in the journal Biology Letters, Australian researchers say the feathered fossil is indeed the first known bird, despite another study earlier this year suggesting otherwise.

Archaeopteryx had been considered for 150 years to be the first known bird since the first complete specimen was found in Germany in 1861, revealing a combination of reptilian and and bird features. But Chinese researchers asserted recently that a new and closely related fossil, Xiaotingia zhengi, was a bird-like dinosaur - therefore suggesting that Archaeopteryx was also a dinosaur.

However, the new study, led by Dr Michael Lee, of the South Australian Museum, used a more detailed analyis to show that Archaeopteryx was a bird.

"Archaeopteryx is iconic in palaeontology as the basal bird, however the plethora of discoveries of feathered dinosaurs in China, in particular, has progressively eroded the distinction of just what defines a bird," says one of the authors, Dr Trevor Worthy, a palaeontologist in the UNSW School of Biological, Earth and Environmental Sciences.

"This trend came to a head when Xaiotingia was analysed most recently and in the analysis, Archaeopteryx was found to jump ship, as it were, from the birds to the dromaeosaurs."

However the researchers say that through their methodology Archaeopteryx remains the basal bird and does so with strong statistical support.

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Media contact: Bob Beale, Faculty of Science newsroom | 0411 705 435