Sunday, April 24, 2016

[Paleontology • 2016] A Tiny Titanosaur, Rapetosaurus krausei, from the Cretaceous of Madagascar

Baby Rapetosaurus were only dog-sized a few weeks after hatching.
Scientists have found an adorable fossil: a baby dinosaur. It would've been gargantuan had it lived, but at its death at age two or three months, it was only the size of a golden retriever. It is the only one of its kind, and it promises to shed new light on dinosaur growth rates and parenting.
Photo: R. Martin and K. Curry Rogers |
DOI: 10.1126/science.aaf1509 

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.

Tiny giant
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.

K. Curry Rogers, M. Whitney, M. DEmic, B. Bagley. Precocity in A Tiny Titanosaur from the Cretaceous of Madagascar. Science. 2016; 352 (6284): 450 DOI: 10.1126/science.aaf1509

How to raise a dinosaur? Tiny fossil may tell us via @usatoday
Tiny dinosaur skeleton reveals babies lived on their own from birth via  @HuffPostScience
Rapetosaurus krausei: Tiny titanosaurus was just a few weeks old, scientists say