Bone Study Reveals Dinosaur Size
December 20, 2012

Dinosaurs Were Literally Large In Numbers

Lee Rannals for — Your Universe Online

A new study published in the journal PLOS ONE states dinosaurs may have been bigger than we thought, in terms of ratio.

Scientists have always understood dinosaurs were the largest animals to roam the Earth, but now they find they also had a greater number of larger species compared to all other back-boned animals.

For the study, Queen Mary, University of London researchers compared the size of the femur bone of 329 different dinosaur species from fossil records.

The team measured the length and weight of the femur bone, which is a method recognized in paleontology for estimating a dinosaur's body mass.

Ultimately, the scientists found dinosaurs follow the opposite pattern of body size distribution as seen in other vertebrate species.

Within living mammals, there tends to be few larger species, such as elephants, compared to the smaller animals, such as mice. Our current animal kingdom is abundant in the smaller species, but lacking in the giant species.

The evidence from fossil records suggests there were many species of larger dinosaurs and few small species during this time period.

"What is remarkable is that this tendency to have more species at a bigger size seemed to evolve quite early on in dinosaurian evolution around the Late Triassic period, 225 million years ago, raising questions about why they got to be so big," Dr. David Hone from Queen Mary's School of Biological and Chemical Sciences, said in a statement.

According to Hone, the researchers findings support a previous theory on the dinosaur kingdom.

"Our evidence supports the hypothesis that young dinosaurs occupied a different ecological niche to their parents so they weren't in competition for the same sources of food as they ate smaller plants or preyed on smaller size animals," Hone said.

He added there are other, living animals that tend to follow the same patterns the dinosaurs did.

"In fact, we see modern crocodiles following this pattern - baby crocodiles start by feeding off insects and tadpoles before graduating onto fish and then larger mammals," Hone said in the release.

Dr. Eoin Gorman, also from Queen Mary's School of Biological and Chemical Sciences, said there is growing evidence dinosaurs produced a large number of offspring, which were vulnerable to predation because of their smaller size.

"It was beneficial for the herbivores to grow to large size as rapidly as possible to escape this threat, but the carnivores had sufficient resources to live optimally at smaller sizes," Gorman added. "These differences are reflected in our analyses and also offer an explanation why other groups do not follow a similar pattern."

He also pointed out several modern-day vertebrate species are almost entirely carnivorous, while many of the herbivores are warm-blooded, which limits their size.