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 Scientists on Thursday announced the discovery of fossils of a
baby Rapetosaurus the size of a big dog that apparently starved to
death during a drought several weeks after hatching from its
soccer-ball-sized egg.
Unlike many animal babies, particularly humans, the hatchling
Rapetosaurus had adult proportions, meaning it likely did not need
significant parental support and was actively foraging for plants
rather than waiting for momma to feed it.
Such babies are known as "precocial," as opposed to "altricial"
offspring that have different body dimensions from adults, cannot
get around by themselves and require considerable parental support
for food and protection, Macalester College paleontologist Kristi
Curry Rogers said.
 "The main conclusion was that this is the first evidence for a truly
precocial dinosaur: one that matured rapidly and without parental
care," Adelphi University paleontologist Michael D'Emic added.
Rapetosaurus lived about 67 million years ago, not long before the
demise of the dinosaurs, and was the largest creature in Madagascar
at the time.
The baby, known from a partial skeleton including limb bones, pelvic
bones, fingers, toes and several vertebrae, was probably around 4
feet (1.2 meters) long from head to tail and weighed between 50 and
90 pounds (23-40 kg) when it died.
An adult Rapetosaurus was probably around 40 feet (12 meters) long,
a little more than a school bus, and weighed around 16 tons, roughly
2-1/2 times as much as an elephant, Curry Rogers said. It was a
medium-sized member of a dinosaur group called titanosaurs, which
included the largest land animals ever on Earth.
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Titanosaurs were part of a larger assemblage of dinosaurs called
sauropods, known for their long necks, long tails and voracious
appetite for plants.
D'Emic said the researchers looked at the microstructure of the
baby's bones to see preserved cavities that once held cells, blood
vessels and nerves. The density and organization of those indicated
a rapidly growing individual, and there was even evidence for bone
repair, suggesting an active lifestyle and fast metabolism, D'Emic
added.
Examples of precocial animals today include most lizards, snakes and
reptiles, certain birds and some large mammals including wildebeest.
"Precocial young can avoid predation on their own, and there is a
much smaller chance of the entire brood succumbing to predation at
once," Curry Rogers said.
The research was published in the journal Science.
(Reporting by Will Dunham; Editing by Sandra Maler)
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