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A pregnant Tyrannosaurus rex that roamed Montana 68 million years ago may be the key to discerning gender differences between theropod, or meat-eating dinosaur, species. Researchers have confirmed the presence of medullary bone – a gender-specific reproductive tissue – in a fossilized T. rex femur.
Beyond giving paleontologists a definitively female fossil to study, their findings could shed light on the evolution of egg laying in modern birds.Image credit: Mark Hallett
