On the hollow inside surface of the T-Rex femur, Schweitzer discovered scraps of bone that gave a surprising amount of information about the dinosaur that made them. Details that defied the idea that these same samples were thought to being some 68 million years old!
Bones may seem as steady as stone, but they’re actually constantly in flux as the organism lives out its lifespan. Pregnant females use calcium from their bones to build the skeleton for a developing fetus. Therefore, females form a calcium-rich structure called medullary bone on the inside of their leg and other bones which indicates this dinosaur was a pregnant female.
“It’s a girl and she’s pregnant,” Schweitzer recalls telling her lab technician when she looked at the fragments.
https://www.smithsonianmag.com/science-nature/dinosaur-shocker-115306469/
How could such tissues and details remain even after thousands of years. The discovery of medullary bone in a female T Rex pushes such conjecture to new heights.
“Dinosaur Shocker”; Probing a 68-million-year-old T. rex, Mary Schweitzer stumbled upon astonishing signs of life that may radically change our view of the ancient beasts
By Helen Fields, Smithsonian Magazine, May 2006
[…] First unearthed in 2000, then finally fully excavated in August of 2005, after years of hard and dedicated field work, Mary Schweitzer Paleontologist, PhD, Paleo-biologist, Evolutionary Biologist, and Molecular Biologist, of North Carolina State University in Raleigh unearthed a Tyrannosaurus Rex fossil in Hell Creek Montana with soft tissues. The T. Rex was nicknamed ‘B. Rex’ and later ‘Bob Rex’ until later when the discovery identified Bob as a pregnant eighteen year old female with medullary bone. […]