Which came first?

Look: Dinosaur embryo appears freakishly like a chicken in an egg

by Jennifer Walter
Lida Xing

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Dinosaurs are thought to be the ancestors of today’s birds.

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Many prehistoric beasts shared traits with avian species today: They hatched from eggs, had beaks, and were covered in feathers.

These similarities may have started before they even hatched.

A newly-described fossil egg reveals an uncanny resemblance to unhatched chickens.

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Researchers writing in the journal iScience on December 21 detail a near-complete baby theropod dinosaur fossil, still in its egg.

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Identified as an Oviraptorsaur, a group of dinosaurs known for their coats of feathers and hollow, toothless skulls, it looks surprisingly familiar.

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Nicknamed “Baby Yingliang,” the fossil was unearthed in Ganzhou, a city in southern China where a number of therapod fossils have turned up in recent years.

Such excellently preserved, unhatched dinosaur fossils are extremely rare, the researchers say.

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Baby Yingliang’s remains, which date to the Late Cretaceous period up to 72 million years ago, could reveal new details of early development in dinosaurs — and today’s chickens.

The dinosaur is curled up like how chicken embryos position themselves to prepare for hatching.

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“This little prenatal dinosaur looks just like a baby bird curled in its egg, which is yet more evidence that many features characteristic of today’s birds first evolved in their dinosaur ancestors.”

Stephen Brusatte, study co-author

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In chickens, this posture is known as tucking and typically occurs right before the bird hatches.

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The researchers looked at other types of dinosaur eggs, such as those of sauropods and other theropods, but this behavior appears unique to Oviraptosaurs — so far.

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More fossil evidence is needed to establish when dinosaurs started tucking — and how widespread it was across species. But Baby Yingliang reveals a previously unknown commonality with its modern descendants.