Dwarf Dinosaurs On The Island

What are these - reptilian versions of Shetland Ponies? Nevertheless, it is interesting what island life can do to make animals small. But some animals - for example, Galapagos Tortoises - grew larger than their forbears, not smaller, because only large animals are big enough to survive the feast-or-famine swings of equatorial weather associated with El Niño:

The idea of the small prehistoric beasts on Hateg Island, Romania, was proposed 100 years ago by the colourful Baron Franz Nopcsa, whose family owned estates in the area.

He found that many dinosaur remains on Hateg were half the size of their close relatives in older rocks in England, Germany, and North America.

The baron's theory has been tested for the first time by Professor Mike Benton at the University of Bristol, and six other authors from Romania, Germany, and the United States.

The team found that the Hateg Island dinosaurs were indeed dwarfs and not just young dinosaurs.

A favourite theme of evolutionary ecologists is whether there is an ''island rule'' - where large animals isolated on islands evolve to become smaller.

Three species of the Hateg dinosaurs - the plant-eating sauropod Magyarosaurus and the plant-eating ornithopods Telmatosaurus and Zalmoxes - are half the length of their nearest relatives elsewhere.

The team examined these three dinosaurs, each represented by many specimens. They found no evidence of any large bones such as they would expect to find in their normal-sized relatives.

More importantly, a close study of the bones confirmed that the dinosaurs had reached adulthood so they were not just underdeveloped youngsters.

Detailed studies by Martin Sander in Bonn and his students also show that the bone histology (the microscopic structure) is adult.

The idea of ''island dwarfing'' is well-established in other cases. There were dwarf elephants on many of the Mediterranean islands during the past tens of thousands of years.

These well-studied examples suggest dwarfing can happen quite quickly, the team believes.

Professor Benton, a palaeontologist, said: ''The general idea is that larger animals that find themselves isolated on an island either become extinct because there is not enough space for a reasonably-sized population to survive, or they adapt.

''One way to adapt is to become smaller, generation by generation.''