Sauropods also had plenty of neck vertebrae, up to 19. In contrast, nearly all mammals have no more than seven, from mice to whales to giraffes, limiting how long their necks can get. (The only exceptions among mammals are sloths and aquatic mammals known as sirenians, such as manatees.)
Moreover, while pterosaur Arambourgiania had a relatively giant head with long, spear-like jaws that it likely used to help capture prey, sauropods had small, light heads that were easy to support. These dinosaurs did not chew their meals, lacking even cheeks to store food in their mouths; they merely swallowed it, letting their guts break it down.
"Sauropod heads are essentially all mouth. The jaw joint is at the very back of the skull, and they didn't have cheeks, so they came pretty close to having Pac Man-Cookie Monster flip-top heads," researcher Mathew Wedel at the Western University of Health Sciences in Pomona, Calif., told LiveScience.
"It's natural to wonder if the lack of chewing didn't, well, come back to bite them, in terms of digestive efficiency. But some recent work on digestion in large animals has shown that after about 3 days, animals have gotten all the nutrition they can from their food, regardless of particle size.
"And sauropods were so big that the food would have spent that long going through them anyway," Wedel said. "They could stop chewing entirely, with no loss of digestive efficiency."
What's a Long Neck Good For?
Furthermore, sauropods and other dinosaurs probably could breathe like birds, drawing fresh air through their lungs continuously, instead of having to breathe out before breathing in to fill their lungs with fresh air like mammals do. This may have helped sauropods get vital oxygen down their long necks to their lungs.
"The problem of breathing through a long tube is something that's very hard for mammals to do. Just try it with a length of garden hose," Taylor said.
As to why sauropods evolved such long necks, there are currently three theories. Some of the dinosaurs may have used their long necks to feed on high leaves, like giraffes do. Others may have used their necks to graze on large swaths of vegetation by sweeping the ground side to side like geese do. This helped them make the most out of every step, which would be a big deal for such heavy creatures.
Scientists have also suggested that long necks may have been sexually attractive, therefore driving the evolution of ever-longer necks; however, Taylor and his colleagues have found no evidence this was the case.
In the future, the researchers plan to delve even deeper into the mysteries of sauropod necks. For instance, Apatosaurus, formerly known as Brontosaurus, had "really sensationally strange neck vertebrae," Taylor said. The scientists suspect the necks of Apatosaurus were used for "combat between males — fighting over women, of course."
Taylor and Wedel detailed their findings online Feb. 12 in the journal PeerJ.
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