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The oldest belly button ever discovered in reptiles and mammals was discovered last week in a 125-million-year-old dinosaur fossil found in China 20 years ago. Due to its preserved state, the fossil retained exceptional purity and integrity of the remains.
The discovery of a long umbilical scar on a Psittacosaurus specimen was made by palaeontologists from the Chinese University of Hong Kong (CUHK) using laser-stimulated fluorescence (LSF) ) to a Psittacosaurus fossilized skin sample. The findings were published in the international journal BMC Biology.
The researchers said the size, smoothness, and location of the umbilical scar ruled out trauma or infection as the cause, adding and that it is the same scar as living lizards and crocodiles.
Unlike mammals, this reptilian navel is a slit-like opening that connects the embryo to the egg's yolk sac and other membranes. The yolk sac retracts into the dinosaur's body either just before or just after hatching, leaving behind a hole in the abdominal wall that closes and looks like a long scar.
Although scientists have hypothesized that egg-laying dinosaurs might have such scars, this is the first time they have been found in flightless dinosaurs.
The two-meter-high Psittacosaurus (name meaning “parrot lizard”) lived in the early Cretaceous, was an herbivore, and had a beak similar to that of a parrot .
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