Paleontologists have discovered the oldest navel known to science — and the first ever found in a non-avian dinosaur — in a 125-million-year-old fossil of a parrot-beaked biped in China.
The faint navel mark belongs to a reptile of the genus Psittacosaurus, who lived during the Cretaceous period (145 million to 66 million years ago). Scientists detected the long, thin trace of an umbilical scar when they exposed the fossil to a focused beam of laser light. The scar is a slight misalignment in the pattern of the skin and scales over the dinosaur abdomen and is the reptilian equivalent of a mammalian navel.
Unlike fetal mammals, which obtain their nutrients from the placenta, bird and reptile embryos are nourished by a yolk sac connected to the abdomen via several blood vessels. When these embryos hatch, the yolk sac is completely absorbed into the body, leaving a linear abdominal scar that usually heals in a few days or weeks. But in some reptiles, like alligators, the umbilicus can last beyond sexual maturity. This discovery of the fossilized belly button is the first indication that dinosaurs may also have umbilical scars that never completely disappeared. The researchers published their findings on June 7 in the journal BMC Biology.
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“This one Psittacosaurus is probably the most important fossil we have for studying dinosaur skin,” said vertebrate paleontologist Phil Bell, a senior professor at the School of Environmental and Rural Sciences at the University of New England in Armidale, Australia. said in a statement. “But it continues to produce surprises that we can bring to life with new technologies like laser imaging.”
The fossil, known as SMF R 4970, is a Psittacosaurus mongoliensisan early type of ceratopsian, a group of beaked herbivores that later included Triceratops. Measuring 6 feet (1.8 meters) in length and 4 feet (1.2 m) in height, P. mongoliensis it was probably a highly social creature, living in groups and looking for seeds to grind and nuts to crack in its sharp beak. Discovered about 20 years ago, the fossil of the horn-cheeked creature is remarkably well preserved, which has allowed scientists to document individual scales, tail bristles and first dinosaur butt ever discovered (described at the time as “perfect” and “unique”), Live Science previously reported.
The researchers were able to make detailed observations of the specimen’s belly because of its excellent preservation and because of the animal’s position at death – the creature fossilized while lying on its back. This dinosaur death pose allowed the study authors to apply a technique called laser-stimulated fluorescence (LSF) to the abdomen of the ancient reptile. The glow of a beam of laser light on the specimen caused it to emit a very faint glow, which helped scientists analyze the preserved skin along its belly, one scale at a time. His investigation revealed a 10-centimeter-long scar that did not appear to have been caused by physical trauma or illness.
“Using LSF images, we identified distinct scales that surrounded a long umbilical scar on the Psittacosaurus copy, similar to [scars in] certain live lizards and crocodiles,” said paleontologist Michael Pittman, assistant professor at the School of Life Sciences at the Chinese University of Hong Kong, in the statement. “We call this type of scar a belly button, and it’s smaller in humans. . This specimen is the first dinosaur fossil to preserve a belly button, due to its exceptional state of preservation.”
Scientists estimated the age of the dinosaur by comparing the length of its femur to those of others. Psittacosaurus specimens, and found it to be about 6 or 7 years old – close to sexual maturity. This revealed that the navel persisted into the early stages of the creature’s life, like these scars on modern alligators.
While the fossil specimen offers rare information about dinosaur biology, it is also the subject of a fierce repatriation controversy. Unearthed from an unknown region of China sometime in the 1980s or 1990s, it was allegedly smuggled out of the country and into European underground markets before being purchased and displayed in 2001 at the Senckenberg Museum in Frankfurt, Germany, according to Nature. (opens in new tab). Attempts to repatriate the fossil to China by Chinese and European researchers have been made, researchers reported in 2001 in the journal Nature. (opens in new tab)but ownership of the fossil is still disputed.
“There is an ongoing debate over the legal ownership of this specimen and efforts to repatriate it to China have not been successful. Our international team of Australian, Belgian, British, Chinese and American members all expect and support an amicable solution to this ongoing debate.”, the researchers wrote in their article.
Originally published on Live Science.