Over the years many theories have been offered. Some thought the dinosaurs grew big because of the richer oxygen content in the atmosphere. But the evidence only supports that theory for insects like the prehistoric centipedes and dragonflies.
Others like the proponents of the Inflating Earth Theory, argue that in the past the Earth was one-third smaller and had much less gravity. The large dinosaurs, they say, could not even stand or walk in today’s gravity.
But the data gleaned by scientists over the decades has tended to discredit both those theories.
While the ability to breathe in huge quantities of air was a factor, the atmosphere’s higher oxygen content didn’t play a critical role. Nor is there any hard evidence to suggest the Earth had a much weaker gravitational field.
Quite simply, the largest sauropods—like the Argentinosaurus that was the biggest of them all—had a better pair of lungs and were designed to eat fast and eat a lot. They ate so much, in fact, that a few of them could strip a small forest in one day.
That’s not too surprising when considering its size: 140 feet in length and weighing as much as 180,000 pounds.
Yet, theoretically, even a behemoth like Argentinosaurus fell short of the theoretical limit land animals could reach. According to P. Martin Sander, a professor of vertebrate paleontology at the University of Bonn, the limit is in the neighborhood of 150 to 200 tons—a whopping 400,000 pounds. Since nature abhors a vacuum, that mean’s it’s still possible sauropods larger than the Argentinosaurus remain to be found.
Exhibit opens featuring large dinosaurs
A new exhibit at the American Museum of Natural History in New York City is focusing on the large dinosaurs and how they got so big. It features one of the crown jewels of the sauropod era, a smaller version of the mighty Argentinosaurus called Mamenchisaurus, Sander explained to LiveScience in an interview. He’s the co-curator of the exhibit.
The primary reason that dinosaurs were able to grow to such enormous size was their ability to eat massive quantities of food. To accomplish this they were designed to eat foliage without the need to chew. In a way they were like modern day vacuum cleaners sucking up food and gulping it down.
“Chewing limits body size,” Sander explained. As an animal gets larger, it must expend more energy to chew. Eventually, the process of chewing will burn up almost as much energy as the food ingested. At that point of diminishing returns, the animal couldn’t survive. The big sauropods avoided that by being able to swallow food without chewing it.
Although all the really big dinosaurs had teeth, they didn’t chew. Not only did they not have the muscular structure to enable chewing, but their teeth were designed to bite. Other teeth acted like rakes helping the animals to efficiently strip trees of leaves and swallow the pulpy mass.
To maintain their size, dinosaurs like Mamenchisaurus had to eat as many as 100,000 calories a day from a diet comprised solely of vegetation.
Massive dinosaur bodies were models of efficiency. They were literally built using economies of scale. Their long necks allowed them to forage without having to expend much energy and they had light skulls and very tiny brains.
The era of the giant sauropods was one of nature’s most successful experiments. They roamed the planet for about 140 million years while humans have only been Earth’s master for less than three million years.
The World’s Largest Dinosaurs
April 16, 2011 through January 2, 2012
American Museum of Natural History in New York City