Babies of long-necked plant-eaters called Titanosaurs that include the largest animals ever to walk on land hatched from eggs no bigger than a soccer ball but they grew rapidly without any rapidly without any parental care after hatching, research on a newly discovered young sauropod fossil shows.
The research is based on a study of the life of a young Rapetosaurus, a titanosaurian sauropod buried in the Upper Cretaceous Maevarano Formation of Madagascar.
"This is our first opportunity to explore the life of a sauropod just after hatching, at the earliest stage of its life," said lead researcher Kristi Curry Rogers of Macalester College in St. Paul, Minnesota, US.
The baby behemoths were active, capable of a wider array of maneuvers than adult members of their species, and did not need parental care after hatching like some other dinosaurs, the researchers said.
The preserved partial skeleton was so small that its bones were originally mistaken for those of a fossil crocodile, Curry Rogers said.
"This baby's limbs at birth were built for its later adult mass; as an infant, however, it weighed just a fraction of its future size," Curry Rogers pointed out.
The team studied thin-sections of the tibia and used a high-powered CT scanner to get a closer look at the microstructures preserved inside the limb bones.
The detailed microscopic features of the Rapetosaurus bones revealed patterns similar to those of living animals and made it possible for the scientists to reconstruct the beginning of the dinosaur's post-hatching life.
"We looked at the preserved patterns of blood supply, growth cartilages at the ends of limb bones, and at bone remodeling," Curry Rogers said.
"These features indicate that Rapetosaurus grew as rapidly as a newborn mammal and was only a few weeks old when it died," she noted.
The tiny titanosaur was mobile at hatching and less reliant on parental care than other animals. Baby sauropods like Rapetosaurus were somewhat like miniature adults, Curry Rogers said.
The researchers believe that drought might have caused the demise of this baby Rapetosaurus.
Clues came from its cartilage growth plates, which bear a striking resemblance to the modified growth cartilages that occur during starvation among living vertebrates.
When taken in the context of the intensely drought-stressed ecosystem represented in the Maevarano Formation, it's clear that this Rapetosaurus had it rough, Curry Rogers said.
"Between its hatching and death just a few weeks later, this baby Rapetosaurus fended for itself in a harsh and unforgiving environment," she said.
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