New exhibition tackles question of how dinosaurs grew so large

By Gisela Ostwald Apr 25, 2011, 8:51 GMT

New York - Scientists have long sought the answer as to why dinosaurs known as sauropods grew to such titanic proportions and how they could possibly have eaten enough food to survive.

A new exhibition at the American Museum of Natural History (AMNH) in New York entitled 'The World's Largest Dinosaurs' looks to shed some light on the issue.

Sauropods roamed the Earth for over 140 million years and these long-necked, long-tailed dinosaurs grew as large as three articulated trucks in length and weighed up to 10 times as much as an adult elephant.

The exhibition goes beyond the usual fossils and has at its centerpiece a life-sized, detailed model of a 20-metre Mamenchisaurus. It also includes Apatosaurus (formerly known as Brontosaurus), Brachiosaurus and Diplodocus.

No animal has come close to the size of the larger sauropods since since a meteor impact led to their extinction, something German paleontologist Martin Sander from the University of Bonn and leader of the research team has been investigating.

Sander assembled a team of 30 to 40 people from different disciplines to try and solve the mystery and uncover the circumstances that allowed the sauropods to exist.

'It is a great honour that we were asked to come here to help with the concept and content of this exhibition,' Sander told the German Press Agency dpa in New York.

Sander is not only a co-curator of the exhibition at the AMNH, his German-Swiss team of paleontologists, biologists and other scientists has also published a book called 'Biology of the Sauropod Dinosaurs.'

'We concentrated on the physical traits unique to the sauropods that weren't present in other large animals,' explains Sander.

The answer to why sauropods grew so large seems to lie in their biology rather than in the characteristics of their environment.

Research shows the largest dinosaurs did not need to move very much thanks to their long necks. They also swallowed their food whole without chewing, allowing the creatures to obtain enough energy by digesting up to 500 kilos a day.

By not chewing, sauropods also dispensed with the need for facial muscles and large heads. 'Chewing food seems to limit body size evolutionarily because it makes the head heavier,' says Sander.

Their parental care was also primitive, laying eggs twice a year, a trait that helped sauropods escape extinction for so long. 'Live births are more seldom and riskier with larger animals,' Sander explains.

One question that puzzled the researchers was whether the size of sauropods was related to lower atmospheric oxygen during the Triassic and Jurassic periods.

'Explaining and understanding their respiratory system was the most difficult part of the exhibition,' says Sander.

The life-size model of the Mamenchisaurus at the exhibit stretches to approximately 20m in length, complete on one side with skin and hair.

The other side gives an insight into the animal's metabolism, showing that the Mamenchisaurus survived on just 10 heartbeats per minute compared to 700 for the average mouse and 72 for an elephant.

Other interactive exhibits show how the animals ate, moved and defended themselves from attacks.