But now a 70-million-year-old Tyrannosaurus rex discovered in Montana has apparently yielded the improbable, scientists reported yesterday: soft tissues, including blood vessels and possibly cells lining them, that "retain some of their original flexibility, elasticity and resilience."...Moreover, an examination with a scanning electron microscope showed the dinosaur's blood vessels to be "virtually indistinguishable" from those recovered from ostrich bones. The ostrich is today's largest bird, and many paleontologists think birds are living descendants of some dinosaurs....They said the extraction of DNA for studies of dinosaur genetics and for cloning experiments was only a long shot, though at least reasonably possible.
It sounds as if this could have been overlooked in the past as well too me.