Diatryma

Gastornis is an extinct genus of large, flightless birds that lived from the middle Paleocene to the middle Eocene epochs of the Paleogene. Most known fossils have been recovered from Europe, although species historically assigned to the genus have also been reported from North America and Asia. Several genera, including the well-studied Diatryma, have traditionally been regarded as junior synonyms of Gastornis. This classification has been challenged by more recent studies, however, and some researchers regard Diatryma as a distinct and valid genus.