Until now, the infant years of a baby titanosaur had been a mystery. Studies conducted on the bones of a young rapetosaurus, a titanosaurian sauropod, recently unearthed in the Upper Cretaceous Maevarans Formation in Madagascar, unlock some secrets.
A research team comprised of scientists from Macalester College, the University of Washington, Adelphi University and the University of Minnesota studied the dinosaur’s small, preserved partial skeleton.
Judy Skog, a program director in the National Science Foundation’s (NFS) Division of Earth Sciences, which funded the research along with the NFS’s Division of Environmental Biology says,
These scientists employed several lines of evidence to investigate growth strategies in the smallest known post-hatching sauropod dinosaur.
The research team studied thin sections of the tibia using a high-powered CT scanner to get details of microstructures preserved inside the limb bones. The details revealed a similar pattern found in the hatching lines of today’s reptiles. This made reconstruction of the sauropod’s early life possible. The lines also proved similar to those in extinct mammals.
The study states,
Limb bones grew isometrically throughout its development — Cortical remodeling, limb isometry and thin calcified hypertrophic metaphysical cartilages indicate an active precocial growth strategy.
The rapetosaurus’s time of hatching was determined and its weight estimated to be around 7.7-pounds (3.4 kilograms). Hatchlings were usually the size of a soccer ball. This baby had a greater range of movement than an adult. Unlike other dinosaur groups like theropods and orinthischians that required prenatal care, these hatchlings were precocial, able to move independently after birth. They resembled miniature adults.
Kristi Curry Rogers, from Macalester College led the study says,
It’s intriguing that these animals developed quickly to function on their own, much like some birds and herding mammals of today — We looked at the preserved patterns of blood supply, growth cartilages at the ends of limb bones, and at bone remodeling. These features conclude that rapetosaurus grew as rapidly as a newborn mammal and was only a few weeks old when it died. — Between its hatching and death just a few weeks later, this baby rapetosaurus fended for itself in a harsh and unforgiving environment.
The baby’s life was short-lived due to the severe drought of the Maevarano Formation. Its cartilage growth plates resembled those that occur during starvation among living vertebrates. At death, it weighed 40 kilograms and was 35 centimeters tall at the hip.
Curry Rogers sums up,
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. This is our first opportunity to explore the life of a sauropod just after hatching, at the earliest stage of its life.