Speaker 1: Welcome to brain Stuff production of iHeart Radio, Hey brain
Speaker 1: Stuff Lauring Vogel bomb here. In the past thirty years,
Speaker 1: paleontologists and other fossil hunters have uncovered a wealth of
Speaker 1: dinosaur eggs. China has been home to many of these
Speaker 1: fossil fines, but researchers have also discovered nesting grounds in Argentina, Canada,
Speaker 1: South Africa, and the United States. This is a big change.
Speaker 1: Until the nineteen nineties, fossilized eggs were rare fined. By
Speaker 1: studying these eggs, scientists can learn about a lot more
Speaker 1: than how dinosaur is reproduced. Eggs and their positions within
Speaker 1: nesting grounds can yield lots of clues about dinosaur behavior.
Speaker 1: The structure of the eggs can help scientists figure out
Speaker 1: whether dinosaurs were more like birds or reptiles, and in
Speaker 1: a very few cases, a fossilized egg can show paleontologists
Speaker 1: what a dinosaur embryo looked like. The trouble is, in
Speaker 1: spite of these recent fines, dinosaur eggs are still a
Speaker 1: lot rarer than dinosaur bones. On top of that, very
Speaker 1: few eggs that have survived until today still contain their embryos.
Speaker 1: This is because several specific conditions have to exist for
Speaker 1: an embryo to fossilize. First, an egg containing a healthy
Speaker 1: embryo has to be buried in sediment. A freshly laid
Speaker 1: egg which hasn't it developed an embryo won't help. The
Speaker 1: egg also has to be intact. If there's a crack
Speaker 1: in the shell big enough for anything to escape, the
Speaker 1: material inside will leak out before fossilization can occur. This
Speaker 1: buried egg then has to survive the slow process of fossilization.
Speaker 1: Groundwater containing minerals seeps through the shell, slowly replacing the
Speaker 1: non mineral components of the bones inside. Most of the time,
Speaker 1: soft tissues in fluids inside the egg break down or
Speaker 1: dissipate instead of becoming fossils. The shell itself is already
Speaker 1: made of calcium, so it doesn't physically change much during
Speaker 1: the fossilization process, but if all goes well, the embryonic
Speaker 1: skeleton inside turns to rock. Scientists don't always have to
Speaker 1: break open dinosaur egs to see what's inside. Occasionally, researchers
Speaker 1: will find fossilized hatchlings in a nest with whole eggs,
Speaker 1: giving them a good clue as to what the eggs contain.
Speaker 1: Other eggs are found broken or weathered, leaving their embryos exposed.
Speaker 1: For example, a fossil bed discovered in Patagonia was so
Speaker 1: full of eggs and egg fragments that became known as
Speaker 1: Aoka mohuevo, meaning more eggs. Because of the sheer number
Speaker 1: of eggs, paleontologist speculate that the entire area was submerged
Speaker 1: in a flood, allowing lots of silt to cover all
Speaker 1: the eggs at once. At the Aoca Mohuevo site, researchers
Speaker 1: found whole eggs containing embryos, as well as eggs shell
Speaker 1: fragments that contained parts of embryos. In a few cases,
Speaker 1: skin that rested against the inside of the shell became
Speaker 1: fossilized as well, giving scientists a glimpse at what embryonic
Speaker 1: dinosaur skin looked and felt like. Based on the embryos
Speaker 1: found with the eggs, scientists theorized of the dinosaurs that
Speaker 1: laid these eggs were most likely souropods, which are four
Speaker 1: legged dinosaurs with long necks. When there are no convenient
Speaker 1: hatchlings or broken shells nearby, researchers can use computerized axial
Speaker 1: tomography scans or cat scans to try to figure out
Speaker 1: what's inside an egg. A CAT scan, also known as
Speaker 1: a CT scan, takes lots of X rays of an object.
Speaker 1: A computer then combines these X rays to form a
Speaker 1: three dimensional view of the object. Using cat scans, scientists
Speaker 1: can figure out whether the egg contains any embryonic material.
Speaker 1: If it does, they can determine the size and shape
Speaker 1: of the embryo within the shell. The other predominant technique
Speaker 1: used to figure out what's in an egg involves destroying
Speaker 1: the egg shell. By soaking the egg in a mild
Speaker 1: acid bath, scientists can slowly remove the shell. This process
Speaker 1: is time consuming, but it can eventually reveal the entirety
Speaker 1: of skeleton inside. Once the embryonic skeleton is uncovered, researchers
Speaker 1: saturated with plastic to preserve it. But just because an
Speaker 1: acid bath or a cat scan reveals the shape of
Speaker 1: an embryo doesn't mean scientists can figure out what kind
Speaker 1: of dynas or it would have grown up to be.
Speaker 1: Many dinosaurs looked significantly different as hatchlings, adolescents, and adults.
Speaker 1: In some cases, a dinosaur's embryo may look nothing like
Speaker 1: any known adult dinosaur specimen. The size and shape of
Speaker 1: eggs also adds to the complexity. For instance, researchers have
Speaker 1: asserted that two dissimilar eggs, one round and the other oblong,
Speaker 1: both contained a dinosaur known as a their xenosaur. In
Speaker 1: two thousand and five, paleontologists found a fossilized over wraptor
Speaker 1: pelvis with eggs inside. The pelvis contained two eggs, and
Speaker 1: their positioning suggests that the species may have formed and
Speaker 1: laid eggs in clutches of two, the way that many
Speaker 1: birds do. This contrasts with the way that many reptiles
Speaker 1: lay large batches of eggs at once. Today's episode was
Speaker 1: written by Tracey V. Wilson and produced by Tyler Clang.
Speaker 1: Brain Stuff is production of iHeart Radius How Stuff Works.
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