A recent study has extrapolated the genome size of dinosaurs who lived from about 230 to 65 million years ago. This extrapolation was made from osteocytes (bone cells) found in fossils and comparing with various living species, mostly birds. The findings are somehow surprising, as the genome size was determined to be quite small for such large animals.
But don't worry, T-rex fans. Having a small genome doesn't imply inferiority. As the researchers noted, a lungfish has a bigger genome than a human.