Paleontologists have discovered the oldest navel known to science – and the first ever found on a non-avian dinosaur – on 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, which lived during the Cretaceous period (145 to 66 million years ago). Scientists spotted the long, thin trace of an umbilical scar when they exposed the fossil to a concentrated beam of laser light. The scar is a slight misalignment of the pattern of skin and scales on the dinosaur abdomen and is the reptile equivalent of a mammalian navel.
Unlike fetal mammals, which derive their nutrients from a placenta, the embryos of birds and reptiles are nourished by a yolk sac connected to their abdomen by various blood vessels. When these embryos hatch, the yolk sac is completely absorbed into the body, leaving a linear abdominal scar that usually heals within days or weeks. But in some reptiles, like alligators, the umbilical scar can last beyond sexual maturity. This fossilized navel discovery is the first indication that dinosaurs may also have had umbilical scars that never completely disappeared. The researchers published their findings June 7 in the journal BMC Biology.
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“This Psittacosaurus specimen is probably the most important fossil we have for studying dinosaur skin,” said vertebrate paleontologist Phil Bell, senior lecturer in the School of Environmental and Rural Sciences at the University of New England at Armidale, Australia. said in a press release. “But it continues to yield surprises that we can bring new technologies like laser imaging to life.”
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) long and 4 feet (1.2 m) high, P. mongoliensis was probably a very social creature, living in groups and searching 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 incredibly well preserved, allowing scientists to document individual scales, tail hairs and the first dinosaur asshole ever discovered (described at the time as “perfect” and “unique”), Live Science previously reported.
Researchers were able to make detailed observations of the specimen’s belly due to its exquisite preservation and the animal’s position in 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 ancient reptile’s abdomen. Shining 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. Their investigation revealed a 4-inch-long (10 centimeters) scar that did not appear to have been caused by physical trauma or disease.
“Using LSF imaging, we identified distinctive scales that surrounded a long umbilical scar in the Psittacosaurus specimen, similar to [scars in] some living lizards and crocodiles,” said paleontologist Michael Pittman, an assistant professor at the School of Life Sciences at the Chinese University of Hong Kong. “We call this type of scar a navel, and it’s smaller in the man. . This specimen is the first dinosaur fossil to retain a navel, which is due to its exceptional state of preservation.”
Scientists estimated the age of the dinosaur by comparing the length of its femur to those of other Psittacosaurus specimens, and found it to be about 6 or 7 years old – approaching sexual maturity. This revealed that the navel persisted through the creature’s early life stages, as such scars do in modern alligators.
While the fossil specimen offers rare insight into dinosaur biology, it is also the subject of fierce repatriation controversy. Unearthed from an unknown region of China in the 1980s or 1990s, it was believed to have been smuggled out of the country and into European underground markets before being purchased and put on display in 2001 at the Senckenberg Museum in Frankfurt, Germany, according to Nature. (opens in a 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 a new tab)but the ownership of the fossil is still disputed.
“There is an ongoing debate regarding 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 hope and support a solution to amicable to this ongoing debate,” the researchers wrote in their paper. “We believe it is important to note that the specimen was acquired by the Senckenberg Museum to prevent its sale to private individuals and to ensure its availability for scientific study.”
Originally posted on Live Science.