This CT slice through a hadrosaur tail vertebra (bone of the backbone) shows the vertebra (in a mostly orange colour) and a tooth from a large tyrannosaurid (identifiable, most likely, as Tyrannosaurus) embedded within the vertebra. While there have been plenty of evidence that tyrannosaurids have preyed on hadrosaurs, this is the first evidence that such activity was not post-mortem. This is a dinosaur that was attacked, by a Tyrannosaurus, and lived to see another day.
The main proponent of the idea that Tyrannosaurus was an obligate scavenger (meaning: that during some stage of its life, an individual must eat dead animals) has (arguably) backtracked, claiming the find is not a big deal:
“I’ve long argued that Tyrannosaurus rex was an opportunist like a hyena, sometimes hunting and sometimes scavenging. This provides no evidence to the contrary,” says Jack Horner, a palaeontologist at the Museum of the Rockies in Bozeman, Montana, who served as scientific adviser on the Jurassic Park films.
DePalma et al. 2013 provides the rest of the tale for people with access to PNAS.