Life reconstruction of Europasaurus holgeri. Image credit: Davide Bonadonna (CC BY 4.0)
Dinosaurs, like all animals with spines, had their main sensory organs – the organs that allowed them to listen, taste, see, smell, think and even keep their balance – on their heads. This means that studying their fossilized skulls can provide a wealth of information about how these animals perceived their environment through so-called ‘endocasts’ (digital models of the cavities within the skull).
Endocasts of the skulls of many different dinosaur species already exist, but a small species called Europasaurus holgeri had so far not received this treatment. This sauropod lived in what is now northern Germany during the Late Jurassic period (154 million years ago), and it owed its reduced size to having become isolated on an island, where it became smaller after many generations. Schade et al. wanted to gain a better understanding of certain lifestyle aspects of the biology of E. holgeri, and to be able to compare the endocast anatomy of this species to other dinosaurs. To do this, the team studied the braincases of both very young and mature E. holgeri individuals using a technique called computer tomography.
The approach taken by Schade et al. allowed them to examine and describe in detail the inner cavities that once contained the brain, inner ears, nerves and blood supply of eight different E. holgeri individuals. They found that the inner ears of small and young E. holgeri individuals were almost as large as those of their adult counterparts, and very similar in shape. Given that inner ears have roles in both audition and the sense of equilibrium, this suggests that E. holgeri babies were able to leave their nest very soon after hatching. This makes it likely that the babies of the species were highly developed when they hatched, and could probably feed themselves almost immediately, possibly similar to chickens. Furthermore, the relatively large size of the part of the inner ear responsible for hearing hints at E. holgeri being well able to communicate with other members of the species using sound.
The findings of Schade et al. add to the diversity of the record on the anatomy of the braincases of dinosaurs. Additionally, the results support the idea that sauropods may have been herd-living animals with social interactions that grew very fast and had to be light on their feet very early in life. Finally, comparing the endocasts of E. holgeri to those of other dinosaurs suggests that, beyond a discrepancy in body size, this species was very similar to its larger relatives on the Jurassic mainland.
