T. Rex Bone Indicates Gender and Relationship to Birds

Several months ago I briefly blogged about the discovery of a Tyrannosauraus rex bone that, when de-mineralized and rehydrated, appeared to have retained structures of soft tissue. The same authors (Mary Schweitzer, et al.) are back with another paper in Science which builds on the last one, with interesting results.

Reuters via MSNBC.com reports:

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The bone tissue is strongly similar to that made inside the bones of female birds — and no other living type of animal — when they are producing the hard shells of eggs just before they lay them, said Mary Higby Schweitzer of North Carolina State University in Raleigh.

"In addition to demonstrating gender, it also links the reproductive physiology of dinosaurs to birds very closely. It indicates that dinosaurs produced and shelled their eggs much more like modern birds than like modern crocodiles," Schweitzer told reporters in a telephone briefing.

Female birds produce a layer of bone tissue called medullary bone when they are laying eggs. It is rich in calcium, providing minerals that would otherwise be leached from harder bone material, leaving the bird susceptible to fractures.

This image shows medullary bone (MB) and cortical bone (CB) of T. rex.

Since dinosaurs are thought to be the ancestors of birds, this finding makes sense and strengthens such an argument.

For more on dinosaurs and their relationship to birds, see this page at The Tree of Life web project, which is a pretty cool site--it's worth wandering around.

Creationists were unphased by the last paper--in fact they apparently saw it as evidence supporting young-earth creationism. (For more on this, see here.) It will be interesting to see how they spin this paper.

Update: Coverage from National Geographic News.