What anatomical feature led paleontologists to initially popularize the idea that *Gastornis* was a formidable predator?

Answer

Its sheer size and powerful head structure.

For many years, the sheer size and powerful head of *Gastornis* led scientists to assume it was a formidable predator capable of preying upon the small, emerging mammals of that era.

What anatomical feature led paleontologists to initially popularize the idea that *Gastornis* was a formidable predator?
fossilCenozoicbirdpaleontologyextinct