Dinosaur embryos are a prized find for palaeontologists. A recent discovery of embryonic bones and teeth from the Early Jurassic period of Yunnan, China, has given researchers an even rarer glimpse – early tooth formation in a baby dinosaur.

Carleton University’s Hillary Maddin, professor in the Department of Earth Sciences, was part of an international research team that recently studied the well-preserved embryonic jawbones of an early sauropodomorph dinosaur called Lufengosaurus – a distant relative of the giant, long-necked sauropod dinosaurs. These embryonic dinosaur skeletons are among the oldest in the world and preserve several jaws with teeth still inside.

“The computed tomography (CT) scan data are like a digital dissection,” said Maddin. “We can visualize the shapes and positions of the baby teeth within the tiny jaw, all without destroying this rare fossil.”

For the first time, these unique fossils allowed researchers to compare the development of embryonic teeth to the teeth of hatchlings and adults. Surprisingly, the tooth development was rapid in the unhatched embryos, with multiple generations of teeth coexisting in each tooth position in a wide jaw.

The team discovered that the early embryonic teeth of this early sauropodomorph dinosaur were more like the teeth of some of their descendants, the giant sauropods that had massive batteries of teeth as adults for processing plant material. This discovery enabled the team to propose that the evolution of complex dental batteries and the pencil-shaped adult teeth in the giant herbivorous sauropod dinosaurs may have evolved through paedomorphosis: the retention of embryonic developmental stages in adults.

The similarities between embryonic Lufengosaurus teeth and those of much later-occurring species show that paedomorphosis was a common theme in the evolution of sauropods, the largest and longest-lived land-dwelling animals of all time.

The paper appears in the journal Nature Communications.

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Tuesday, June 2, 2020 in
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