Kristina Curry Rogers, Megan Whitney, Michael D’Emic & Brian Bagley (2016)
Tiny giant suggests that largest dinosaurs were precocial at birth.
Science 352(6284): 450-453
Titanosaurs were the largest land vertebrates to have evolved, but even they had to start small. Curry-Rogers et al. describe a baby Rapetosaurus only 35 cm at the hip at death. Histological and limb analysis suggest that this tiny giant had a much greater range of movement than it would have had as an adult. Furthermore, the work confirms hypotheses that these largest of dinosaurs were precocial, being able to move independently immediately after birth. This pattern differs from that seen in many contemporary dinosaur groups, such as theropods and ornithischians, for which increasing evidence suggests that parental care was important.
Sauropod dinosaurs exhibit the largest ontogenetic size range among terrestrial vertebrates, but a dearth of very young individuals has hindered understanding of the beginning of their growth trajectory. A new specimen of Rapetosaurus krausei sheds light on early life in the smallest stage of one of the largest dinosaurs. Bones record rapid growth rates and hatching lines, indicating that this individual weighed ~3.4 kilograms at hatching. Just several weeks later, when it likely succumbed to starvation in a drought-stressed ecosystem, it had reached a mass of ~40 kilograms and was ~35 centimeters tall at the hip. Unexpectedly, Rapetosaurus limb bones grew isometrically throughout their development. Cortical remodeling, limb isometry, and thin calcified hypertrophic metaphyseal cartilages indicate an active, precocial growth strategy.
Patrick Monahan (2016)
The tiniest titan.
Science 352(6284): 395
Scientists have for some time figured that titanosaurs—a group of massive, long-necked herbivorous dinosaurs—didn't provide much parental care to their offspring. But a lack of fossils from babies meant there was no way to tell for sure. Now, a find of fossil bones from a weeks-old dinosaur provides the first solid evidence that titanosaur babies could fend for themselves. From microstructures inside the bone, researchers discovered that the baby was between 39 and 77 days old and weighed 40 kilograms when it died. The terrier-sized juvenile was able to walk around and likely feed itself, as evidenced by its adultlike proportions and signs of stress in its leg bones. And the shape of the baby's bone cartilage regions points to its untimely death by starvation.