Scaling up: Mega-dino babies were mini adults

by Mary Caperton Morton
Tuesday, August 16, 2016

A baby Rapetosaurus was similar in size to a baby rhinoceros. Credit: D. Vital.

Even the largest dinosaurs to walk the planet had to start out small, hatching out of eggs, but whether these were miniature versions of adults has been a long-standing question. Now a new study looking at fossils belonging to a specimen of Rapetosaurus krausei, a type of titanosaur, that died at just a few weeks of age is revealing just how fully formed some of these eventual giants were at an early age.

In the Cretaceous, adult titanosaurs grew to lengths of over 15 meters, but the specimen of R. krausei, discovered in Madagascar, was only 35 centimeters tall at the hip. Despite its minuscule size, the baby already displayed adult-like proportions of the head, limbs and spine.

Further investigation of the fossils by Kristina Curry Rogers, of Macalester College in St. Paul, Minn., and colleagues using bone histology and X-ray computed tomography revealed a compact growth pattern, indicating that the baby was already very mobile and that its limbs likely retained the same shape throughout its life.

The evidence helps confirm a long-suspected hypothesis that unlike species of theropods and ornithischians, for whom ample nesting evidence has been found, large sauropods didn’t provide much parental care to their young, in part because they were precocious from birth, able to move and feed on their own soon after hatching. However, mortality rates for young were also high, with this youngster likely dying from starvation at about 2.5 months of age, the team wrote in Science.

© 2008-2021. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the expressed written permission of the American Geosciences Institute is expressly prohibited. Click here for all copyright requests.