The Field Museum is home to one of the most important fossils ever discovered.

It’s called the Archaeopteryx. It once had feathers, hollow bones, clawed wings, 50 tiny teeth and a long bony tail. It’s one of the earliest known dinosaurs that also qualifies as a bird.

“It’s actually a missing link,” said Dr. Julian Siggers, president and CEO of the Field Museum. “It’s the evolutionary link between dinosaurs and birds. Most people think dinosaurs went extinct; they didn’t, they just evolved into birds.”

The Chicago Archaeopteryx is only the 13th fossil of its kind known to be in existence. It was unveiled Monday to the media. Scientists at the museum said it’s the earliest bird known to science that proves Charles Darwin’s theory of evolution.

The fossil was unearthed by quarry workers in 1990 and has been in the hands of private collectors ever since. It was brought out of its rock casing by three preparators over 1,400 hours.

“The bird fossil has hollow bones, so if you touch something there is nothing solid underneath,” explained Chief Preparator Akiko Chinya. “If you put too much pressure then the bone collapses, so we had to be extra careful with that.”

A coalition of supporters helped the museum procure it. It first arrived two years ago, and most of the skeleton was obscured by a top layer of rock. It was extracted from that casing using only hand tools and dental drills.

The fossil will go on public display starting Tuesday in a one-month temporary exhibit. It will be removed in June for more research and to be prepared for its permanent display in the fall.