A rare specimen of the titanosaur Rapetosaurus krausei from the Cretaceous of Madagascar sheds light on early life in the smallest stage of one of the largest dinosaurs, says a team led by Macalester College paleontologist Kristina Curry-Rogers.
Baby Rapetosaurus krausei is compared to neonatal mammals: the dinosaur was only 14 inches tall at the hip, and weighed around 40 kg when it died a few weeks after hatching. This body size is similar to that of some large-bodied mammalian newborns: black rhinoceros calves are 35-45 kg at birth and stand a little taller at the shoulder than baby Rapetosaurus krausei at 25.6 inches (65 cm); African elephants are close to 39 inches (1 m) high at the hip and weigh between 90 and 120 kg at birth; hippo newborns are the closest in both height and mass to the specimen of Rapetosaurus krausei, checking in between 24-45 kg at birth with a shoulder height of 14.6 inches (37 cm). Image credit: D. Vital.
Rapetosaurus krausei is a member of the dinosaur group Titanosauria that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous period.
The species is estimated to have reached a maximum length of about 50 feet (15 m).
While several fossils of Rapetosaurus krausei have been analyzed to date, very little is known about this titanosaur around the time of hatching.
Analysis of the new fossil by Dr. Curry-Rogers and co-authors suggests that the baby Rapetosaurus krausei they studied, who died between the age of 39 and 77 days, weighed roughly 3.4 kg when it hatched.
Just several weeks later, when it likely succumbed to starvation in a drought-stressed ecosystem, it had reached a mass of 40 kg and was 14 inches (35 cm) tall at the hip.
The team used bone histology and X-ray computed tomography to understand its growth pattern.
“Histological and limb analysis suggest that this tiny giant had a much greater range of movement than it would have had as an adult,” Dr. Curry-Rogers and her colleagues said in a paper published this week in the journal Science.
“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.”
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Kristina Curry Rogers et al. 2016. Precocity in a tiny titanosaur from the Cretaceous of Madagascar. Science, vol. 352, no. 6284, pp. 450-453; doi: 10.1126/science.aaf1509
