December 12, 2012
Massive Sauropod Dinosaurs Ate More To Get Much Needed Nitrogen
Brett Smith for redOrbit.com - Your Universe Online
A pair of U.K. biologists has revived an older and heavily debated theory that suggests sauropod dinosaurs reached their massive sizes due to the plants they ate.
About ten years ago, plant ecologists from South Africa originally formulated this theory; however their ideas have fallen out of favor with many dinosaur researchers. According to a paper from David Wilkinson of Liverpool John Moores University (LJMU) and Graeme Ruxton of University of St Andrews, Scotland, the early-2000s theory shouldn´t be discounted just yet.
“There is a view amongst many sauropod researchers that sauropods must have relied heavily on gut microbes for fermentative digestion of their plant food,” the researchers wrote in their paper, which was recently published in the journal Functional Ecology. “So, large body size effectively gives a much larger microbial fermentor.”
The researchers suggest in their paper that some scientists confuse two different issues in thinking about how sauropods got so big. Wilkinson and Ruxton assert that how much energy a plant contains is not as important as how much nitrogen is in the plant.
They say that the high carbon-to-nitrogen ratios of the plants in their diet forced sauropods to take in a large plant diet just to get enough nitrogen into their system. They noted that the plants that comprised the sauropods´ diet were not as diverse as they are for today´s herbivores. Nitrogen-rich flowering plants had yet to proliferate and the typical sauropod diet most likely included ferns, conifers and other ℠pre-angiosperms.´
Wilkinson said they decided to examine the “modern examples” of what sauropods probably ate. The biologists then postulated what the results of a sauropod subsisting on a modern diet might be.
"This new study makes a first attempt to calculate in more detail the implications of this idea. It suggests that it may have been to the advantage of young sauropods trying to get enough nitrogen to have a metabolism rather like modern mammals” said Wilkinson.
“A mammal (and possibly also small sauropods) would get rid of this surplus as heat, but this would not be possible for a really large dinosaur,” he continued. Because the juvenile sauropods had a relatively large surface area to volume ratio, they could effectively radiate heat better than their older, bigger counterparts.
The paper also theorized that since young sauropods didn´t have a large digestive tract for processing a plant-based diet–they may have been omnivorous (subsisting on plant and animal matter), possibly eating small snails during their development.
While they may have benefited from their long digestive system, Wilkinson said adult sauropods would not have had the option of radiating off excess energy and “may have laid down fat reserves instead. So one can even speculate that they may have had humps of fat rather like modern-day camels."
Wilkinson also noted that the massive sauropods are not in his typical field of study, but as an ecologist who studies modern animals, he was drawn to them “because they´re so weird.”