Two teams were able to identify collagen fragments from the femur of a 68-million-year-old Tyrannosaurus rex. This specimen was discovered in California. The collagen fragments were analysed for the first time in 2007.

_{Source: Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry (2007) / Reanalysis of Tyrannosaurus rex Mass Spectra (2009)}