Dwarf Dinosaurs Discovered in Germany
for National Geographic News
|June 7, 2006|
Meet the smallest of the biggest.
Compared to other sauropodslong-necked, small-headed, plant-eatersa newfound dinosaur species is downright tiny.
The largest sauropods, the brachiosaurs, were the biggest land animals ever, measuring 85 feet long (26 meters long).
The new species, however, grew to only 20 feet (6.2 meters) long.
Researchers found 11 different specimens of these dwarf sauropods, both adults and juveniles, in Germany. The animals lived on an island, a type of environment where limited food resources often encourage species to evolve into smaller forms over generations.
The quarry where the 150-million-year-old fossilized bones were found, near the town of Goslar in northern Germany, was part of an island during the late Jurassic period.
"We're talking here about a spectacular find, with skull material, which is very rare in sauropods," said Octávio Mateus, a co-author of the study and a professor at the Museum of Lourinhã and the New University of Lisbon, in Portugal.
"In North America they've found a few [sauropods with skull material], but not in Europe. We're very excited, because [in the new find] we have the juveniles and the adults, and this allows us to understand how they grew during their lifetimes."
The authors have named the genus Europasaurus holgeri"Europasaurus" meaning "reptile from Europe" and "holgeri" after Holger Lüdtke, who discovered the first of the E. holgeri bones. Lüdtke, a private collector, turned the find over to the researchers.
The fossils were found in an unlikely location, according to Mateus.
"This was not supposed to happen," he said, "because all those layers were supposed to be marine layers containing only marine animals. We didn't expect to find dinosaurs, but we did."
A report on the discovery appears in the June 8 issue of Nature.
There is little doubt that the animals they found were a dwarf speciesnot small or deformed individuals of a larger species.
To examine the skeleton, the team cut sample sections of the bone core so thinly that they were translucent. This allowed them to observe the bone structure under a microscope.
The researchers expected to see juvenile featuresbone filled with the blood vessels that allow growthbecause no one had ever seen an adult sauropod so small.
But they were surprised: They mainly saw the kind of fibrous bone structure typical of adult bones.
Some bones, though, had more blood irrigation than othersa sure sign they belonged to younger, still growing animals.
"Dinosaur bones have growth rings, similar to but a bit more complicated than those you find in trees," Mateus said. "We can actually see the yearly growth of the older animals, which you don't see in the juveniles."
The analysis of these growth rings, he says, revealed conclusively that these smallest of sauropods were dwarves.
E. holgeri, according to Mateus, is conclusive proof that island dwarfism is an evolutionary fact.
The new study "proves for the first time that dwarfism happens," he said, "and we hope this can have implications for the study of all the other dinosaurs in the world."
There are implications for dinosaur behavior as well.
"We're seeing a herd of several animals of several different ages," Mateus said. "This means the babies are living with the adults. They live in packs."
One of the discoverers of the "hobbit" humans on the Indonesian island of Flores, Peter Brown studies early-human fossils at the University of New England in New South Wales, Australia. (See a map showing the site of the hobbit find.)
(See pictures of the tiny humans of Flores.)
Island dwarfism has been proposed as a reason for the small size of the hobbitsHomo floresiensisand Brown finds the new sauropod report interesting.
"It's not surprising that the large sauropod dinosaurs dwarfed under island conditions with limited available calories," Brown said. "Their food requirements must have been enormous."
No doubt their food requirements were smaller than those of the mighty brachiosaurs, but even the smallest sauropod must have had a healthy appetite.
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