One of my favorite stories to cover over the years at Discovery concerns the Transylvania dwarf dinosaurs. To recap, in 1895, the sister of an eccentric palaeontologist called Franz Baron Nopcsa discovered small dinosaur bones on their family estate in Transylvania. Nopcsa interpreted these as being the remains of dwarfed animals that had once lived on an island.
Nearly everyone thought he was nuts.
Science, however, is now proving Nopsca's theories to be valid.
The latest proof, described in the current issue of the Proceedings of the National Academy of Sciences, has to do with the structure of the dinosaur bone fossils found on the Transylvania islands. (Transylvania is an historical region in present-day Romania.) The bones help to shoot down the biggest argument against dwarf dinosaurs, which is that the fossils found for them just belonged to younger dinos.
A team of researchers, led by Koen Stein and Martin Sander from Bonn University, found that at least one of the identified Transylvania dinosaurs, Magyarosaurus dacus, never grew any larger than a horse. Keep in mind that Magyarosaurus was a sauropod. These were plant-eating dinosaurs known for their stocky bodies, long necks, tiny heads and long tails. Some sauropods weighed around 100 tonnes and were among the world's largest animals.
It's believed that Magyarosaurus was even related to the enormous sauropod Argentinosaurus, which some think grew to 115 feet in length.
(Magyarosaurus; Credit: Mihai Dumbrava, liliensternus.deviantart.com)
The microstructure of Magyarosaurus' bones tells the different size story.
"It's astonishing that the microanatomy of these bones has been preserved for us to study after 70 million years," said Stein, who carried out the research as part of his PhD studies. "Bone is a living tissue, and throughout an animal's life it is constantly dissipating and building up again." Humans, for example, have completely resorbed and rebuilt their skeleton by the time they are fully grown. This also occurred in sauropod dinosaurs. "We were able to distinguish these rebuilding features in Magyarosaurus, which prove that the little dinosaur was fully grown," Stein explained.
Sander added: "An animal the size of a horse may not seem like a dwarf to most people but, in sauropod terms, it's tiny!"
(Koen Stein holding a Magyarosaurus bone in his hand. The skeleton of Argentinosaurus is behind him. Credit: Jose Carballido/Koen Stein/Uni Bonn)
Islands have caused other large animals to evolve into dwarfs. Fossils of dwarf elephants and hippopotamuses have been excavated on Mediterranean islands like Sicily, Malta and Cyprus. It's theorized that limited resources and fewer predators lead to the size reductions on islands. With less food, you simply don't grow as much. And with fewer predators, there isn't as much evolutionary advantage to growing larger for defense.
Sander said, "Our study shows that dinosaurs on islands were subject to the same ecological and evolutionary processes that shape modern mammals."
Tags: Dinosaurs, Extinct Animals, Late Cretaceous Dinosaurs, Paleontology, Prehistoric Animals
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