Scientists discover ancient dinosaur "belly button" fossils! Where is the dinosaur belly button and what does it look like?

According to a paper published in the journal BMC Biology, scientists have discovered the first complete dinosaur "navel" fossil from a dinosaur fossil unearthed in my country in 2002! This discovery was made by scientists from the Chinese University of Hong Kong and a team of international paleontologists.

This fossil is 120 million years old and is the oldest and most complete dinosaur "belly button" fossil found by the scientific community so far.

The dinosaur in this fossil is a Psittacosaurus, about 2 meters long. Psittacosaurus was a herbivore that lived in Asia during the Early Cretaceous period 120 million years ago. It is a genus of the Ceratopsian family Psittacosauridae. It has a hooked beak similar to that of a parrot, along with other dinosaurs such as Protoceratops and Triceratops. Based on its body shape and age, scientists believe that Psittacosaurus may be the ancestor of most ceratopsian dinosaurs.

Previously, the "navel" of the dinosaur fossil had not been noticed by scientists until scientists used an imaging technique called laser-induced fluorescence (LSF) to discover the dinosaur's "navel" on the dinosaur skin fossil.

Laser-induced fluorescence technology can use lasers of a certain frequency band to stimulate some skin molecules preserved in the rock matrix, making the petrified skin and other soft tissues invisible to the naked eye emit fluorescence in the dark, thus revealing the true appearance of dinosaurs. Previously, scientists have used this technology to observe the scales and feathers on dinosaur fossils to study the evolution of dinosaurs.

It sounds strange that dinosaurs had "belly buttons", but this belly button was not that belly button.

The so-called belly button is generally only found in humans and other placental mammals. The belly button is the scar left after the umbilical cord (the channel for transporting nutrients and excreting waste) is disconnected from the fetus' body after birth. Of course, the belly buttons of placental mammals are also different. For example, the belly button of a human is concave, while the belly button of a cat is usually flat.

It should be noted that live-bearing animals must be mammals, but not all mammals are live-bearing. For example, the platypus is one of the few egg-laying mammals. Some live-bearing mammals, such as marsupial mammals like kangaroos, do not have a placenta, so they do not have a belly button.

Dinosaurs are reptiles that lay eggs, so they don't have "belly buttons" in theory. However, before the dinosaur embryo hatches, its body is directly connected to the yolk sac of the dinosaur egg through a slit-like abdominal opening. The yolk sac stores a large amount of yolk, which can provide nutrients for embryonic development, similar to the function of the umbilical cord.

When dinosaurs were born, they had a long, thin scar on their abdomens. This scar is what scientists call the dinosaur "belly button," and it stayed with the dinosaurs throughout their lives. Scientists say that reptiles all have something on their bodies that is equivalent to a belly button.

Researchers said that the "belly button" found on the Psittacosaurus dinosaur fossil has morphological characteristics similar to those of some living crocodiles, with a long umbilical scar surrounded by unique scales.

The discovery of the dinosaur's "belly button" was possible not only with the help of new technology, but also because the dinosaur fossil was preserved in a very special state. The skin tissue could be identified through LSF imaging technology, unlike many dinosaur fossils that are basically just a skeleton left.

Scientists are very excited about this and believe that using LSF imaging technology, they may be able to discover dinosaur "belly buttons" in other dinosaur fossils.

Source: Science Exploration