The oldest "navel"!

Text ｜ Xu Rui

A kind of planting dinosaur that lived in China today, a pimaco, may have an umbilical cord scar that is equivalent to mammals.

Related studies were published in "BMC Biology" on June 7.

"During the regular inspection of the specimen, I found some strange signs ... When I saw it, the" umbilical cord scar "appeared in my mind!" Said Phil Bell at the University of New England, Australia.

Picture source: Phil Bell

Most mammal embryos are nutritious from the placenta through the umbilical cord.

In the end, the umbilical cord will fall off and leave scars or navel on the abdomen.

Among birds and reptiles, oval embryos are obtained by blood vessels attached to the yolk cystic.

After it hatch, the yolk sac is absorbed into the body and leaves a linear scar on the abdomen. But unlike human navel, this scar usually disappears after a few days to a few weeks.

And people who can also spawn have a umbilical cord scar that lasts more than several weeks, people are still unclear.

Bell and colleagues used laser to inspire fluorescence technology to imagine the scars on parrot mouth dragon fossils. The results showed that the scar was about 10 cm long, and there were small scales around, which means that it was unlikely that it was caused by physical trauma.

"The scars left by the injury will have very obvious signs of injury, such as the scales may be destroyed and lost the normal appearance. In fact, the scales may not regenerate at all, leaving only the smooth skin."

Bell said, "In contrast, the scars we saw on this parrot mouth dragon fossil are very regular, and there are clear scales on both sides. feature."

By comparing the length of this specimen with the length of the 6 -year -old parrot mouth dragon stock, the research team determined that the individual is also about 6 years old, which may be close to sexual maturity.

"In modern animals, if the umbilical cord scar still exists in the first few weeks after hatching, then it will accompany the animals for the rest of their lives. In view of this parrot mouth dragon around 6 years old, there is no doubt that this scar will always exist, and it is likely that it is likely This is the case of all individuals of this species. "

Bell said, but the above conclusions need to be further studied to confirm. "The newly discovered fossils may change our explanation at any time, but this is also part of science."

At present, the research team is not clear about the distribution of umbilical cord scars in different dinosaur species.

"By observing modern crawled animals, we boldly guess that 5%of adult dinosaurs may have umbilical cord scars." Bell said that the research team hopes to solve this problem by discovering more dinosaurs "belly button".

Related thesis information:

https://doi.org/10.1186/s12915-022-01329-9

"China Science News" (2022-06-14 The 2nd edition of the original title "This dinosaur has the" belly button "")

Edit | Zhao Lu

Capture | Guo Gang

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