2011
Tumbler Ridge Museum Foundation
Before Aaron Fredlund made his discovery and report to the PRPRC in 2011, there were no tyrannosaur trackways (a series of footprints made by the same animal) known in the world. This discovery changed all of that. These trackways are from tyrannosaurs from 72 million years ago. It could be the trackways of either Albertosaurus or Gorgosaurus. The trackways were made by adult tyrannosaurs traveling together. This was not only the first report of tyrannosaur trackways, but the first hard evidence that adult tyrannosaurs traveled (at least part time) in groups.
[Paper Link: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103613]