A nearly complete but strongly flattened skull of the ancient bird species Diatryma geiselensis has been discovered, after being misidentified and kept in a museum collection in Germany for over six decades.
Skull remains of Diatryma geiselensis from the Middle Eocene of the Geisel valley, Germany. Scale bars – 5 cm. Image credit: Mayr et al., doi: 10.26879/1438.
Diatryma geiselensis was approximately 1.4 m (4.6 feet) tall and was member of an extinct order of giant flightless fowl called Gastornithiformes.
“Some of the most unusual birds that populated the northern hemisphere in the Early Cenozoic belong to the Gastornithiformes,” said Michael Stache, a geological preparator at the Geiseltalmuseum of Martin-Luther-Universität Halle-Wittenberg, and his colleagues.
“These large flightless birds became known to science in 1855, when paleontologists described the remains of a giant flightless bird from the Early Eocene of Meudon near Paris as Gastornis parisiensis.”
“Except for a fossilized bone from the Early Eocene of central China, all fossils of these birds stem from the Late Paleocene and Eocene of Europe and North America.”
Diatryma geiselensis lived in what is now the Geiseltal region of Germany around 45 million years ago (Eocene epoch).
“At that time, the Geiseltal was a warm, tropical swamp,” the paleontologists said.
“Ancient horses, early tapirs, large land crocodiles as well as giant tortoises, lizards and numerous birds lived here.”
About 35 cm (13.8 inches) in length, the fossil skull of Diatryma geiselensis was unearthed in 1958.
The specimen was stored in two parts at the Geiseltalmuseum of Martin-Luther-Universität Halle-Wittenberg and, as per the index card, was mistaken for crocodilian remains.
“The find was initially misidentified as a crocodile skull,” Dr. Stache explained.
“We realized the mistake and got down to work, restoring and then analyzing the piece of skull.”
“We combined the fossil with another object from the collection, reconstructing an almost entire skull.”
According to the researchers, the new Diatryma geiselensis specimen represents only the second skull of a gastornithiform known so far.
“This discovery shows once again that many of the most interesting discoveries in paleontology occur in museum collections,” said Dr. Gerald Mayr, curator of the ornithological collections at the Senckenberg Research Institute Frankfurt.
“Just a few years ago, nobody would have thought that the Geiseltal Collection would contain such surprises.”
“This research expands our understanding of the Eocene epoch in the Geiseltal even though the excavations were completed long ago,” Stache said.
“Up 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.”
“Diatryma was probably a rare guest in the Geisetal. Otherwise, there would probably be more fossils.”
A paper on the findings was published in the journal Palaeontologia Electronica.
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Gerald Mayr et al. 2025. Resurrecting the taxon Diatryma: A review of the giant flightless Eocene Gastornithiformes (Aves), with a report of the first skull of Diatryma geiselensis. Palaeontologia Electronica 28 (3): a57; doi: 10.26879/1438
