Reconstruction of an extinct animal that lived near 60 million years ago, right after the domain of the dinosaurs and before the domain of the mammals. That is called the Paleocene era.
Diatryma or Gastornis, as known in the US and Europe respectively, but with little certainty if are different genres or the same. At that time, the continents were joined. Anyway, they are called “terror birds”, but again, studies have shown that their diet may not have been just about eating small mammals nor proto-horses.