What is "bathornis"

Bathornis ("tall bird") is a lineage of extinct birds related to modern day seriemas, that occurred in North America about 37–20 million years ago. Like the also closely related and extinct phorusrhacids, it was a flightless predator, occupying predatory niches in environments classically considered to be dominated by mammals. It was a highly diverse and successful genus, spanning a large number of species that occurred from the Priabonian Eocene to the Burdigalian Miocene epochs.