Europasaurus—the Shrunken Sauropod
11:15 pm
Sauropods were the great group of “brontosaur”-type dinosaurs whose members included some of the largest animals ever to walk the Earth. But despite the group’s super-sized tendencies, sauropods were still subject to the constraints imposed by their local environments. A paper in the latest issue of Nature reports on a sauropod species that became dwarfed due to isolation on small islands in Jurassic Europe.
Europasaurus models
Model and Photo credit: Dinopark Münchehagen
From this press release.
Europasaurus holgeri (“Holger Lüdkte’s European reptile”) was a livestock-sized sauropod discovered in Northern Germany. It is known from a bonebed containing the remains of at least 11 individuals, ranging in size from 1.7 to 6.2 meters long. While larger than many animals, 6 meters long is positively pint-sized for a sauropod—its closest relatives were 3 to 5 times bigger.
An analysis of the fossils’ bone histology shows that, while the smaller specimens clearly came from juveniles, the largest individual was full grown when it died. The growth marks also suggest that, despite relatively rapid growth during childhood, Europasaurus grew more slowly than other sauropods, which likely helped it maintain its (relatively) diminutive stature into adulthood.
Europasaurus’ small size was likely an adaptation to its environment. The preservation of the fossils suggests that they were not transported terribly far before burial—a small herd probably perished and were quickly washed out to sea. The only nearby land at that time was an archipelago of small islands stretching across what is now Europe. The largest of these islands was less than 200,000 square kilometers in area, which may have been too small to support a population of large sauropods. The scaled-down Europasaurus, however, seems to have managed just fine.
A phylogenetic analysis places little Europasaurus between the 18-meter-long Camarasaurus and the gargantuan 30-meter-long Brachiosaurus. This suggests that 6.2-meter Europasaurus evolved from much larger ancestors who were forced to put a brake on their growth in order to survive in a land of limited resources.
Afarensis and Palaeoblog both have the story. The Nature article’s figures and supplemental material (including additional figures) are freely accessible.
Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur. 2006. P. Martin Sander et al. Nature 441: 739-741.
Update 6/8: More Europasaurus on the web compiled here.