Island Dinos were "dwarfs"

Sauropods were subject to the same evolutionary processes as today's mammals

Life reconstruction of Magyarosaurus © Mihai Dumbrava, liliensternus.
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Sauropods such as the famous Brachiosaurus or Argentinosaurus are mainly known for their gigantic body measurements. However, an international research team has now discovered, based on the fossil bone structure, that the sauropod dinosaur Magyarosaurus dacus, a close relative of the giant argentinosaurus, never grew larger than a horse. The reason: Magyarosaurus was an islander.

The scientists, led by the University of Bonn, now report on the results of their new study in the journal Proceedings of the National Academy of Sciences (PNAS).

Remains of dwarfed islanders

In 1895, the palaeontologist's sister, Franz Baron Nopcsa, discovered small dinosaur bones on the family estate in Transylvania. Nopcsa interpreted these as the remains of dwarfed islanders. Amongst these findings, some bones belonged to a sauropod dinosaur named Magyarosaurus dacus, which Nopcsa named after his homeland.

The research team led by Koen Stein and Professor Martin Sander from the University of Bonn had now sawed the fossil bones of the dwarfed dinosaur and studied their microstructure for study purposes. "It is amazing that the microanatomy of bones has been preserved after 70 million years, so that we can study it, " says Stein, who conducted the research as part of his doctoral thesis. "Bone is a living tissue, and in the course of an animal's life, it is continually degraded and rebuilt."

For example, humans have their skeletons completely resorbed and replaced with new bones until they are fully grown. This is also true for sauropod dinosaurs. "We were able to differentiate these renewal features in the Magyarosaurus to prove that the small dinosaur was fully grown, " explains the researcher. display

Koen Stein with Magyarosaurus lower leg bone in hand. In the background, the lower legs of Argentinosaurus in the Dino exhibition in the Bonn Museum Koenig. © Jose Carballido / Koen Stein / Uni Bonn

Tiny under giants

Whether Magyarosaurus was a dwarf or not has long been the subject of much discussion among palaeontologists. Sander says, "An animal the size of a horse may not seem like a dwarf to most people, but as far as sauropods are concerned, that's tiny!" Found as Magyarosaurus in Transylvania at the beginning of the 20th century Although Palopontist Nopcsa suspected that Magyarosaurus was a dodgy islander, he could not prove it. Meanwhile, there are many indications of the correctness of his theory, such as the fossils of verzwergten elephants and hippos, which are found on Mediterranean islands such as Sicily, Malta and Cyprus.

However, science followed another path. Because in the next few decades, other researchers found more large sauropod bones at the site of the discovery and concluded that Magyarosaurus was only a juvenile, while the larger bones were from mature individuals.

Structures in a section through a Magyarosaurus bone. Koen Stein / Uni Bonn

New study brought the proof

However, the study now presented proved conclusively that Nopcza's conjecture was correct. "Our study shows that dinosaurs on islands have undergone the same ecological and evolutionary processes as today's mammals, " explains Sander, adding: "We could not They also prove that the larger bones found there belong to another dinosaur species

Whether these come from stray animals that swam from the mainland to the island, or are the ancestors of the ornate Magyarosaurus, remains, according to the scientists, still hidden in the dark of ancient times.

(idw - University Bonn, 03.05.2010 - DLO)