WASHINGTON - Tissue found inside a nearly 70 million year old Tyrannosaurus Rex femur strengthens the theory that today`s birds are direct descendants from the dinosaurs, according to a study in the journal Science.
An analysis of tissue found inside the femur suggests a high likelihood the remains belong to a female T-Rex ready to lay eggs, said Mary Schweitzer, a paleontologist with North Carolina State University, writing in the June 3 edition of the journal.
The tissue -- the first ever discovered inside a dinosaur fossil -- is very similar to medullar tissue found inside the bones of female ratite birds, such as ostriches and emus, that are about to lay eggs, she said.
This tissue is rich in calcium, providing minerals for the egg shell -- minerals that would otherwise be drawn from the bird`s other bones to the point of weakening them.
"In addition to demonstrating gender, it also links the reproductive physiology of dinosaurs to birds very closely," said Schweitzer.
"It indicates that dinosaurs produced and shelled their eggs much more like modern birds than like modern crocodiles," she added.
This discovery was based on well-preserved tissue found inside a Tyrannosaurus Rex femur discovered in an area of Montana, in the central-northern United States, known as Hell Creek Formation, a famous dinosaur fossil site.
The fossil was broken when it was removed from the site, allowing researchers a clear view of its interior.
In March the team claimed to have discovered what appeared to be cells and blood vessels in the same fossils, which belong to a Tyrannosaurus known as MOR 1125, estimated at around 18 years old at death. The finding was reported in March by Science.
The director of the Museum of the Rockies said during a telephone press conference that the museum has remains of 12 Tyrannosauruses, and that the museum was going to break other bones to determine if there are other females.
In May paleontologist Tamaki Sato of Ottowa`s Museum of Natural History in Canada announced the discovery in China of a fossilized female dinosaur carrying two eggs in her body.
06/03/2005 15:11 GMT