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Now, dinosaurs as island-dwarfs

They are found in Germany, and their size is tied to island life

NEW YORK: When you think dinosaurs, you think big. But German scientists say they have discovered a species that evolved into a dwarf, ending up only about one-third the size of its closest known relatives.

The four-legged plant-eater was no lap dog: It measured about 6 metres from its snout to the tip of its long tail and weighed about a tonne. But next to its close evolutionary cousin Camarasaurus, a well-known beast that stretched some 17-plus metres long, this guy was a runt.

What happened? The researchers say it is a case of island dwarfism, the tendency of big species to shrink over time when they find themselves on an island. It is well known among mammals, as with fossil elephants only about 90 cm tall found in Sicily and elsewhere.

Scientists think that in an environment of limited resources, smaller body size becomes an advantage, and so captive populations shrink in body size over long periods of time.

The new creature is the best-documented case of island dwarfism among dinosaurs, said P. Martin Sander, a palaeontologist at the University of Bonn in Germany and lead author of a report in Thursday's issue of the journal Nature.

The creature, dubbed Europasaurus holgeri, lived 154 million years ago in what is now northern Germany. At that time, the region was covered by shallow seas and the creature evidently lived on an island, Mr. Sander said. It is not clear whether a bigger ancestor reached the island from elsewhere and founded a colony, or an existing population found itself isolated by rising sea levels.

Mr. Sander, who specialises in the microscopic structure of bone, got his first look at the fossils in 2003 after an amateur bone-hunter found them in a quarry.

Eventually the scientists realised they had remains from more than 11 animals of varying ages, including at least one fully grown adult. Bone analysis showed that Europasaurus grew more slowly than bigger dinosaurs. Its small size was a normal growth pattern for the species and not the result of disease.

Jeffrey Wilson, Assistant Professor of Geological Sciences at the University of Michigan, called the discovery exciting. — AP

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