The number of chambers in a Tyrannosaurus rex heart cannot be determined because no fossilised heart has been discovered. Conclusions are only guesswork in the absence of any conclusive facts to support a specific amount of chambers in the heart of a T-rex.
Scientists believe that the T-rex probably had a four-chambered heart because it was a warm-blooded animal. Since Tyrannosaurs and other dinosaurs are considered to be the ancient ancestors of birds, their circulatory systems were presumably similar. In 1993, paleontologists discovered a four-chambered heart of a Thescelosaurus; however, scientists have disputed the claim and continue to debate the issue.