"Triceratops" were long thought to have used their horns and frills in combat with predators such as "Tyrannosaurus". The idea was discussed first in 1917 and again 70 years later by Robert Bakker. There is evidence that "Tyrannosaurus" did have aggressive head-on encounters with "Triceratops", based on partially healed tyrannosaur tooth marks on a "Triceratops" brow horn and squamosal; the bitten horn is also broken, with new bone growth after the break. Since the "Triceratops" wounds healed, the "Triceratops" survived the encounter. "Tyrannosaurus" is also known to have fed on "Triceratops". Evidence for this includes a heavily tooth-scored "Triceratops" ilium and sacrum.