May 27, 2022


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Breathtaking Fossil of Baby Dinosaur Tucked in Its Egg Yields New Evolutionary Clues

A exceptional and exquisitely preserved dinosaur embryo tucked inside of an egg like a newborn chook has been unearthed in southern China, delivering an “unparalleled glimpse” into dinosaur improvement.


With a posture that resembles modern chicken embryos shut to hatching, the fossilized embryo is a outstanding discover which raises the likelihood that evolutionary hyperlinks amongst modern-day birds and extinct dinosaurs operate significantly deeper than earlier imagined.

“This dinosaur embryo within its egg is a single of the most lovely fossils I have at any time observed,” paleontologist and examine writer Steve Brusatte at the College of Edinburgh mentioned in a assertion.

“This tiny prenatal dinosaur looks just like a baby hen curled in its egg, which is yet far more proof that numerous attributes attribute of present day birds very first developed in their dinosaur ancestors.”

The embryo lying within its fossilized egg dates among 72 and 66 million decades aged, and was determined as an oviraptorosaur, a team of feathered theropod dinosaurs which had unique toothless, parrot-like beaks and often elaborate crests as properly.

Image of the oviraptorosaur embryo inside its fossilized egg. (Xing et al., iScience, 2021)

Like all other non-avian dinosaurs, oviraptorosaurs went extinct at the conclude of the Cretaceous, all-around 66 million a long time in the past, when an asteroid struck Earth. Birds, evolved from before theropods, somehow survived this function.

This most up-to-date obtain is a prolonged-awaited discovery, and 1 that could possibly not have surfaced experienced museum workers not uncovered the fossil which had been sitting down in storage for about ten years.


“We had been astonished to see this embryo fantastically preserved inside of a dinosaur egg, lying in a bird-like posture,” explained Waisum Ma of the University of Birmingham. “This posture had not been recognized in non-avian dinosaurs before.”

Most of the other non-avian dinosaur embryos uncovered to day are incomplete and their skeletons disjointed, but this fossilized egg contains a single of the most comprehensive non-avian dinosaur embryos found nevertheless – and it indicates tucking actions may have progressed prior to the origin of fashionable birds.

The pretty much-comprehensive skeleton measuring approximately 23.5 cm (9.3 inches) from head to tail is curled up within the elongated fossilized egg, which is practically a complete 7 cm (2.7 inches) shorter than the embryo.

Demonstrating some impressive mobility, the embryo’s clawed forelimbs are nestled on possibly side of its skull, which is tucked in the direction of the base of its looping tail, as you can see in the daily life-like digital reconstruction underneath.

This tucking posture was thought to be one of a kind to birds, which bend their bodies and tuck their heads underneath a wing to ready themselves for hatching. at?v=WxMCOMA0d90

Although the exact developmental phase of the embryo, named ‘Baby Yingliang’, is not recognised, and the connection among tucking and hatching is even now unsure for extinct theropods, this scarce specimen preserved in exceptional element delivers some cracking insights into dinosaur enhancement and evolution.

Comparisons confirmed the embryo lay in a posture unique from their far more distant dinosaur cousins, extended-necked sauropodomorphs, and pretty comparable to hen embryos days prior to they hatch.


Primarily based on these analyses, the team of researchers describing the obtain implies that tucking conduct 1st developed in theropod dinosaurs quite a few tens or even hundreds of thousands and thousands of yrs in the past. Additional embryo fossils – not only of theropod dinosaurs but also of sauropodomorphs – would be wanted though, to set that principle to the test. 

“This new outstanding fossil embryo hints that some early developmental behaviors (tucking) usually thought of as uniquely avian might be rooted extra deeply in the theropod lineage,” write the scientists.

Other options of bird-like reproduction, these types of as dad or mum dinosaurs incubating nests of eggs, have been observed in theropod dinosaurs just before. A single member of the theropod family, a fossilized troodontid, was even identified with its head tucked underneath its forelimb in a sleeping posture typical in modern birds.

But because there are only a handful of fossilized dinosaur embryos found to date, and couple specimens preserved in such element, generating meaningful comparisons of embryonic improvement in dinosaurs is challenging to say the the very least.

“This is why pre-hatching postures and behaviors for dinosaurs have been so unclear,” Ma, Brusatte, and colleagues create.


Employing what materials is accessible, the researchers were being able to evaluate the new find to two other oviraptorid eggs that contains embryos which confirmed some discrepancies in curling posture that may possibly signify a variety of tucking phases in embryo improvement, just times apart.

Right until the next specimen is unearthed, the scientists guiding this most current discovery approach to delve into the embryo’s cranium bones and, employing several imaging tactics, unveil other entire body components that are still coated in rocks.

The analyze was posted in iScience.