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HomeScienceAt Least Some Dinosaurs Had Stomach Buttons, Beautiful Fossil Simply Revealed

At Least Some Dinosaurs Had Stomach Buttons, Beautiful Fossil Simply Revealed


The oldest ‘stomach button’ identified to science has been discovered on an exquisitely preserved horned dinosaur fossil from China.

The slit-like scar comes not from an umbilical wire, because it does in mammals, however from the yolk sac of the egg-laying creature that lived about 130 million years in the past.


Immediately, many dwelling snakes and birds lose their so-called umbilical scar inside days or perhaps weeks of an egg hatching. Others, like grownup alligators, preserve them for all times.

The umbilical scar discovered on the Psittacosaurus dinosaur is extra much like alligators, lasting till a minimum of sexual maturity and probably lengthy after that.

It is the primary instance of a stomach button in a non-avian dinosaur, predating the arrival of ‘latest life’ within the Cenozoic, about 66 million years in the past.

The invention does not imply that each one land dinosaurs sported the identical persistent umbilical scar, however it leaves open the chance.

“This Psittacosaurus specimen might be crucial fossil we’ve for learning dinosaur pores and skin,” says vertebrate paleontologist Phil Bell from the College of New England in Australia. 

“But it surely continues to yield surprises that we will convey to life with new know-how like laser imaging.”

The dinosaur fossil of the Psittacosaurus genus, often called SMF R 4970, was present in China in 2002. It’s exquisitely preserved, exhibiting particular person scales, lengthy plumes of tail bristles, and the first cloaca ever seen in a non-avian dinosaur

Mendacity on its again, the person is virtually presenting all its particulars to scientists.

3 3D reconstruction of a reclining Psittacosaurus exhibiting the lengthy umbilical scar. (Jagged Fang Designs)

Utilizing detailed laser imaging, researchers have now been capable of determine a change within the sample of pores and skin and scales proper the place the dinosaur’s stomach button could be, representing the place the yolk sac was reabsorbed by a younger dinosaur. 

Much like the umbilical wire, the yolk sac is what feeds the rising embryo contained in the egg with oxygen and vitamins; there’s one other related clear sack, the allantois, which collects the waste inside an egg. Earlier than an animal hatches, these connections seal up, leaving a protracted scar. 


Researchers have lengthy hypothesized that egg-laying dinosaurs would possess such a scar, however that is the primary proof to again up that concept.

Fossils of soppy tissue are not often preserved amongst dinosaurs, however SMF R 4970 provides us an unprecedented glimpse at a skinny column of paired scales on an historic stomach.

The common measurement of the scales and their easy margins suggests the scar was not led to by bodily trauma or illness.

As an alternative, its similarity to alligators strongly suggests we’re a stomach button. 

2Laser picture of the Psittacosaurus umbilical scar, with close-ups of its scales. (Bell et al., BMC Biology, 2022)

“Utilizing LSF imaging, we recognized distinctive scales that surrounded a protracted umbilical scar within the Psittacosaurus specimen, much like sure dwelling lizards and crocodiles,” says paleontologist Michael Pittman from the Chinese language College of Hong Kong. 

“We name this sort of scar a stomach button, and it’s smaller in people. This specimen is the primary dinosaur fossil to protect a stomach button, which is because of its distinctive state of preservation.”

From a fully-fledged butthole to a transparent stomach button, the SMF R 4970 fossil has actually put its most non-public components on show.

The examine was revealed in BMC Biology





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