First Dinosaur Fossil with Preserved Belly Button

In the year 2021, a well-preserved herbivorous parrot-beaked dinosaur, also known as Psittacosaurus made headlines as the first-ever fossil specimen having Cloaca. Cloaca is the shared opening of the genitals and digestive tract.

Now with the help of a laser-stimulated fluorescence technique, a team of scientists identified a new hole in the same fossil, a belly button. Because of the excellent preservation state, this marks the first-ever identification of the belly button in the fossil of an amniote, a group of animals that includes mammals, birds, and reptiles, has been found for the first time with such a mark.

The umbilical cord, which leaves an abdominal scar (belly button) once the cord falls off, provides nutrients to a mammalian embryo through a placenta, but in birds and reptiles, it’s quite the opposite. The embryo obtains nutrition from the yolk sac, which changes into a linear abdominal scar after hatching, and then completely disappears, unlike a mammalian belly button. is absorbed into the body as egg hatches, and eventually.

The discovery of the belly button in the fossil means that egg-laying dinosaurs could also have an umbilical scar that doesn’t disappear but instead stayed for more than weeks.