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an extinct fossil bird of the order Diatrymae. It was a cursorial bird with a height about 2 M and was similar to an ostrich. The wings were atrophied, and the legs were strong, with four toes. It had a relatively short neck and a large head, with a massive beak. The Diatryma was the bitter enemy of ancient mammals. It has been found in Eocene deposits in North America and Europe.