Solving Leonardo's round riddle

The fingerprint left a yellowish halo in the sky of the picture

A fingerprint left on a circular Renaissance masterpiece hanging in a Rome museum may hold a clue to who painted the work.

Long attributed to a Dominican friar, the painting depicts Joseph and the Virgin Mary gazing at baby Jesus.

But during a recent restoration a fingerprint was uncovered in the upper left-hand sky portion of the painting.

Art scholars say if it matches that of Leonardo da Vinci, it could prove that the mysterious painting is his.

"Once it was restored, a kind of yellowish halo could be seen in the sky in the upper left," chief restorer Elizabetta Zatti said.

Secret flowers

'The Adoration of the Christ Child' is famous for its round shape, and is known as 'Il Tondo'.

It is one metre (three feet) in diameter and includes precious materials such as lapis lazuli and gold.

The restoration revealed other details that may point to Leonardo's hand in the work.

The Virgin has surprisingly masculine hands, a trait common with many of Leonardo's female figures.

Small flowers that were personal favourites, including wild primroses - representing the resurrection - and blue veronica flowers - symbolising the eyes of the Virgin Mary - were also uncovered.

Photographs of the fingerprint will be compared with a similar imprint on Leonardo's 'Lady with an Ermine' to try to resolve the mystery.