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Speaker 1: Welcome to brain Stuff production of iHeart Radio, Hey brain

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Speaker 1: Stuff Lauring Vogel bomb here. In the past thirty years,

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Speaker 1: paleontologists and other fossil hunters have uncovered a wealth of

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Speaker 1: dinosaur eggs. China has been home to many of these

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Speaker 1: fossil fines, but researchers have also discovered nesting grounds in Argentina, Canada,

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Speaker 1: South Africa, and the United States. This is a big change.

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Speaker 1: Until the nineteen nineties, fossilized eggs were rare fined. By

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Speaker 1: studying these eggs, scientists can learn about a lot more

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Speaker 1: than how dinosaur is reproduced. Eggs and their positions within

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Speaker 1: nesting grounds can yield lots of clues about dinosaur behavior.

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Speaker 1: The structure of the eggs can help scientists figure out

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Speaker 1: whether dinosaurs were more like birds or reptiles, and in

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Speaker 1: a very few cases, a fossilized egg can show paleontologists

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Speaker 1: what a dinosaur embryo looked like. The trouble is, in

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Speaker 1: spite of these recent fines, dinosaur eggs are still a

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Speaker 1: lot rarer than dinosaur bones. On top of that, very

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Speaker 1: few eggs that have survived until today still contain their embryos.

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Speaker 1: This is because several specific conditions have to exist for

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Speaker 1: an embryo to fossilize. First, an egg containing a healthy

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Speaker 1: embryo has to be buried in sediment. A freshly laid

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Speaker 1: egg which hasn't it developed an embryo won't help. The

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Speaker 1: egg also has to be intact. If there's a crack

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Speaker 1: in the shell big enough for anything to escape, the

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Speaker 1: material inside will leak out before fossilization can occur. This

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Speaker 1: buried egg then has to survive the slow process of fossilization.

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Speaker 1: Groundwater containing minerals seeps through the shell, slowly replacing the

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Speaker 1: non mineral components of the bones inside. Most of the time,

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Speaker 1: soft tissues in fluids inside the egg break down or

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Speaker 1: dissipate instead of becoming fossils. The shell itself is already

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Speaker 1: made of calcium, so it doesn't physically change much during

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Speaker 1: the fossilization process, but if all goes well, the embryonic

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Speaker 1: skeleton inside turns to rock. Scientists don't always have to

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Speaker 1: break open dinosaur egs to see what's inside. Occasionally, researchers

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Speaker 1: will find fossilized hatchlings in a nest with whole eggs,

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Speaker 1: giving them a good clue as to what the eggs contain.

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Speaker 1: Other eggs are found broken or weathered, leaving their embryos exposed.

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Speaker 1: For example, a fossil bed discovered in Patagonia was so

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Speaker 1: full of eggs and egg fragments that became known as

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Speaker 1: Aoka mohuevo, meaning more eggs. Because of the sheer number

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Speaker 1: of eggs, paleontologist speculate that the entire area was submerged

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Speaker 1: in a flood, allowing lots of silt to cover all

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Speaker 1: the eggs at once. At the Aoca Mohuevo site, researchers

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Speaker 1: found whole eggs containing embryos, as well as eggs shell

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Speaker 1: fragments that contained parts of embryos. In a few cases,

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Speaker 1: skin that rested against the inside of the shell became

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Speaker 1: fossilized as well, giving scientists a glimpse at what embryonic

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Speaker 1: dinosaur skin looked and felt like. Based on the embryos

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Speaker 1: found with the eggs, scientists theorized of the dinosaurs that

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Speaker 1: laid these eggs were most likely souropods, which are four

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Speaker 1: legged dinosaurs with long necks. When there are no convenient

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Speaker 1: hatchlings or broken shells nearby, researchers can use computerized axial

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Speaker 1: tomography scans or cat scans to try to figure out

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Speaker 1: what's inside an egg. A CAT scan, also known as

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Speaker 1: a CT scan, takes lots of X rays of an object.

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Speaker 1: A computer then combines these X rays to form a

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Speaker 1: three dimensional view of the object. Using cat scans, scientists

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Speaker 1: can figure out whether the egg contains any embryonic material.

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Speaker 1: If it does, they can determine the size and shape

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Speaker 1: of the embryo within the shell. The other predominant technique

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Speaker 1: used to figure out what's in an egg involves destroying

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Speaker 1: the egg shell. By soaking the egg in a mild

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Speaker 1: acid bath, scientists can slowly remove the shell. This process

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Speaker 1: is time consuming, but it can eventually reveal the entirety

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Speaker 1: of skeleton inside. Once the embryonic skeleton is uncovered, researchers

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Speaker 1: saturated with plastic to preserve it. But just because an

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Speaker 1: acid bath or a cat scan reveals the shape of

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Speaker 1: an embryo doesn't mean scientists can figure out what kind

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Speaker 1: of dynas or it would have grown up to be.

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Speaker 1: Many dinosaurs looked significantly different as hatchlings, adolescents, and adults.

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Speaker 1: In some cases, a dinosaur's embryo may look nothing like

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Speaker 1: any known adult dinosaur specimen. The size and shape of

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Speaker 1: eggs also adds to the complexity. For instance, researchers have

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Speaker 1: asserted that two dissimilar eggs, one round and the other oblong,

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Speaker 1: both contained a dinosaur known as a their xenosaur. In

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Speaker 1: two thousand and five, paleontologists found a fossilized over wraptor

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Speaker 1: pelvis with eggs inside. The pelvis contained two eggs, and

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Speaker 1: their positioning suggests that the species may have formed and

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Speaker 1: laid eggs in clutches of two, the way that many

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Speaker 1: birds do. This contrasts with the way that many reptiles

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Speaker 1: lay large batches of eggs at once. Today's episode was

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Speaker 1: written by Tracey V. Wilson and produced by Tyler Clang.

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Speaker 1: Brain Stuff is production of iHeart Radius How Stuff Works.

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Speaker 1: For more on this and lots of other thunderous topics,

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