The almost complete skull fossil can be found in the Geiseltal Collection. Credit: Uni Halle/ Michael Stache.

A fossil discovery from the Geiseltal region in southern Saxony-Anhalt, Germany, has led researchers to identify a unique bird skull.

Around 45 million years ago, a 4.6-foot-tall (1.40 metres) flightless bird called Diatryma roamed the Geiseltal region of Germany.

Now an international team of researchers led by the Martin Luther University Halle-Wittenberg (MLU) and the Senckenberg Research Institute and Natural History Museum in Frankfurt have reported on the bird’s fully preserved skull.

The fossil was unearthed in the 1950s in a former lignite mining area in the Geiseltal in Germany. It was initially misclassified and thus led a shadowy existence until its rediscovery.

The only other place that a similar skull fossil has been found is the USA.

The Geiseltal Collection at MLU comprises 50,000 fossils and is considered a national heritage asset.

These fossils offer unique insights into the evolution of animals and the Eocene Epoch around 45 million years ago.

At that time, the Geiseltal was a warm, tropical swamp. Ancient horses, early tapirs, large land crocodiles as well as giant tortoises, lizards and numerous birds lived here.

Some of the latter were flightless and the largest of these was Diatryma, a herbivore with a gigantic beak which stood around 4.6 feet high.

Reconstruction of the complete skeleton of a Diatryma. Credit: Uni Halle/ Markus Scholz.

Misidentified

For many years no one knew that an almost completely preserved skull of Diatryma was part of the collection.

Michael Stache, a geological preparator at MLU’s Central Repository of Natural Science Collections, said: “The find was initially misidentified as a crocodile skull.”

Stache came across the fossil again by chance several years ago. He realised the mistake and got down to work, restoring and then analysing the piece of skull.

He combined the fossil with another object from the collection, reconstructing an almost entire skull.

Dr Gerald Mayr, a researcher at the Senckenberg Institute, examined the find more closely and realised its importance: the skull clearly belonged to a Diatryma.

Only one other fully preserved skull is known to exist in the world and is housed in the American Museum of Natural History in the USA. 

Mayr said: “This shows once again that many of the most interesting discoveries in palaeontology occur in museum collections.

“Just a few years ago, nobody would have thought that the Geiseltal Collection would contain such surprises.”

Stache also reports that there is great scientific interest in the fossils. Researchers from Germany and abroad come to MLU on a regular basis to investigate the objects.

He said: “This research expands our understanding of the Eocene Epoch in the Geiseltal even though the excavations were completed long ago.”

Until ten years ago, for example, it was assumed that Diatryma hunted prehistoric horses in the Geiseltal. More recent investigations have found that the bird was, in fact, a herbivore. 

There are around 40 specimens of the bird in the Geiseltal Collection, but Stache said: “Diatryma was probably a rare guest in the Geisetal. Otherwise, there would probably be more fossils.”

The study is published in Palaeontologia Electronica.