What Can a Cache of Pterosaur Eggs Teach Us?

A huge cache of ancient pterosaur eggs has been unearthed in China. Learn what this find can tell us about these flying contemporaries of dinosaurs in this epiosde of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain stuff from how stuff works. Hey, they're
brain stuff, Lauren bobil bomb here. Flight is a hard
thing to master. The vast majority of vertebrates can walk, swim,
or do both, but in the history of life on
this planet, only three groups of backboned animals have ever
evolved the ability to fly. Early bats acquired the skill

(00:23):
roughly fifty two million years ago. Feathered dinosaurs began to
experiment with flight back in the Jurassic period. Incidentally, you
probably know of their descendants today as birds. Yet while
birds and bats are still around, the animals that first
pioneered vertebrate flight are long gone. That's because two hundred
and twenty eight million years ago, a flying plade of
reptiles evolved. These were the pterosaurs. Though Hollywood often mislabels

(00:48):
them as dinosaurs, they actually represented a separate, contemporaneous group.
For more than a hundred and sixty million years, dinosaurs
and pterosaurs lived side by side. It was an exciting
time to be an aeronaut. During their reign, the pterosaurs
diversified like crazy. Some species would be comparable to sparrows
in size. Others had wingspans of thirty six feet that's

(01:08):
eleven meters or more, making them the largest flying animals
of all time. Then, sixty six million years ago, the
pterosaurs succumbed to the same mass extinction that wiped out
all non avian dinosaurs. In seventeen eighty four, Italian naturalist
Cosmo Collini became the first person to write a formal
scientific description of a pterosaur skeleton. At the time, he

(01:29):
thought this strange looking animal was some kind of deep
sea creature. But thanks to hard working paleontologists, we've learned
a great deal about these winged wonders. Nonetheless, there are
still some large gaps in our knowledge. One big mystery
involves the early lives of young pterosaurs. The first confirmed
dinosaur nest was unearthed in ninety three. Since then, fossil
hunters have excavated thousands of dino exit sites all over

(01:51):
the world. Yet pterosaur eggs are considerably rarer. None whatsoever
were discovered until two thousand four, when two appeared in
China and a third showed up in Argentina. In eleven,
a fourth egg was found next to the skeleton of
its presumed mother, an adult animal from the genus Darwin,
a terrorist three years later, and another Argentinian egg emerged,
along with five additional Chinese specimens. So until very recently,

(02:15):
the global scientific community hadn't found enough terrasaur eggs to
fill a standard egg carton, but paleontologists just hit the motherload.
In the December seventeen issue of the journal Science, a
Chinese research team announced the discovery of a new site
in China's Gobi Desert containing at least two hundred and
fifteen pterosaur eggs. Sixteen preserved embryos were found there as well,

(02:36):
along with some skeletons from hatchling, juvenile, and adult pterosaurs.
These eggs are roughly a hundred and twenty million years
old and were laid by Hammatteris tiensnsis a crusted toothy
species with an eleven foot wingspan that's about three point
three meters. Terrastaur experts are still trying to assess where
it belongs on the family tree. One such authority is

(02:57):
paleontologist David Hone, who told us in an email that
Hama RAS's closest relatives were most likely various groups of
terrasaurs known for being ocean going or at least coastal
foragers in terms of lifestyle, He says that these animals
would have behaved like today's gulls and albatrosses. The newfound
bounty of eggs was recovered by a team representing the
Beijing based Chinese Academy of Sciences. Most of the shelled

(03:20):
treasures were embedded in a sandstone block that may be
hiding even more clutches that have yet to be revealed.
One reason why this find is so spectacular has to
do with the fragility of terrasaur egg shells. Like modern chickens,
extinct dinosaurs laid hard shelled eggs. Contrast these with the
eggs of present day snakes, whose shells are thin, soft, pliable,
and have the texture of old parchment. Terrasaur eggs resembled

(03:42):
the ladder, a fact confirmed by previous discoveries. Because their
shells were so soft, these rare eggs tend to get
squitched flat by the forces of fossilization. Yet the ones
that this new Chinese site were preserved in three dimensions.
The discovery's implications are still open to debate. Chinese Academy
of Sciences paleontologist Shallon Wang was the lead author of

(04:03):
the paper in the journal Science, which announced this big find.
In it, he and his co authors suggest the site
may have a lot to say about terrasaur parenting. As
Whanging and his colleagues point out, some of the embryo's
lack teeth and their wingbones seem underdeveloped. The paleontologists think
this could mean that newly hatched Hamma terrists could neither
fly nor eat solid food. Thus they would have had

(04:25):
to depend on their parents for protection and sustenance. Other
scientists have disagreed with that conclusion. In present day reptiles,
teeth are one of the last things embryos developed, so
while these developing pterosaurs were toothless, they might still have
grown some choppers before hatching. Also, according to Michael Habib,
a pterosaur specialist at the University of California, the fetal

(04:45):
wings appeared quite robust, meaning the newborns might have been
able to start flying right away. A point of consensus
among paleontologists, though, is that pterosaurs probably didn't brood their
eggs like present day birds. For one thing, as Hone
told us, the extinct reptile simply could not sit like
birds due to the anatomical differences. Also, While terrasaurs were
coated with fuzzy stuff, they lacked feathers, which roosting avians

(05:08):
used to keep their clutches nice and warm. Another leading
expert in modern terrasaur science, one S. Christopher Bennett of
Fort Hayes State University in Kansas, agrees. He said via email,
there's no evidence and no reason to think that pterosaurs
incubated their eggs, or rather, they probably deposited them in sands, soils,
or vegetable matter like modern reptiles. In the past, Bennett

(05:31):
has championed the idea that at least some terrasaurs formed
nesting groups near environments suitable for the hatchlings to feed
and grow safely. He feels the new Hemiiturus site may
lend some credence to that notion, a sentiment shared by
Weighing and his co authors. Bennett added careful excavation of
terrasaur egg deposits could certainly provide evidence as to whether
eggs were buried and whether terrasaurs reused nesting sites year

(05:54):
after year. Today's episode was written by Mark Vancini and
produced by Tristan McNeil. For more in this and lots
of other thunders topics, visit our home planet, how stuff
works dot com.