September 28, 2022
Scientists find oldest belly button in the world on a dinosaur fossil

An “exquisitely” preserved dinosaur fossil has revealed the soft underbelly of a horned dinosaur from China. Specifically, paleontologists using high-tech laser imaging technology found evidence of a dinosaur that lived 125 million years ago and sported a belly button.

The long umbilical scar on the Psittacosaurus specimen is similar to those found on some lizards and crocodiles. Unlike mammals, this reptilian form of belly button is a slit-like opening connecting the embryo to the egg’s yolk sac and other membranes. The yolk sac is absorbed by the dinosaur either immediately before or soon after hatching, leaving behind an opening in the abdominal wall that seals up and appears as a long scar.

“We call this kind of scar a belly button, and it is smaller in humans. This specimen is the first dinosaur fossil to preserve a belly button, which is due to its exceptional state of preservation,” said Michael Pittman, one of the study’s authors and a palaeontologists from the Chinese University of Hong Kong.

The size, smoothness and location of the umbilical scar rule out trauma or infection as the cause, the study says. The abdominal scale’s pattern was uninterrupted, whereas a healed injury would have a “smooth, scale-free connective tissue over the open wound,” the authors note.

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