Sometimes it’s hard to imagine how the planet we call home, with its megacities and serene farmlands, was once dominated by dinosaurs as big as buses and five-story buildings. But recent research has helped deepen our understanding of why the dinosaurs prevailed: The answer may lie in their special bones, structured like Aero chocolate.
Brazilian paleontologist Tito Aureliano discovered that hollow bones filled with tiny air sacs were so important to the survival of dinosaurs that they evolved independently multiple times in different lineages.
According to the study, aerated bones evolved in three separate lineages: pterosaurs, technically flying reptiles, and two lineages of dinosaurs: theropods (ranging from the crow-sized Microraptor to the massive tyrannosaurus rex) and sauropodomorphs (long-necked herbivores, including Brachiosaurus). The researchers focused on the late Triassic period, approximately 233 million years ago, in southern Brazil.
Every time an animal reproduces, evolution throws up random variants in the genetic code. Some of these variants are passed on to offspring and develop over time.
Charles Darwin believed that evolution created “infinitely more beautiful forms.” But some adaptations arise spontaneously over and over again, a bit like having the same hand of cards multiple times. When the same hand keeps showing up, it’s a sign that evolution has come up with an important and effective solution.
The variant that the Brazilian team studied were the bones of the aerated vertebrae, which would have improved the strength of the dinosaurs and reduced their body weight.
Your regular shipments from Amazon or other online retailers come packed in corrugated cardboard, which has the same advantages as aerated bones. It is light, but resistant.
Corrugated cardboard, or as it was initially known, pleated paper, was a highly successful man-made design experiment and is now a part of our everyday lives. It was patented in England in 1856 and was initially designed to support top hats, which were popular in Victorian England and the US at the time.
Three years later, Darwin published his book On the Origin of Species, which described how evolutionary traits that create advantages are more likely to be passed on to future generations than variants that do not.
CT scanning technology allowed Aureliano and his colleagues to peer inside the rock-hard fossils they studied. Without modern technology, it would have been impossible to look inside the fossils and detect the air sacs in the spinal columns.
The study did not find any common ancestors that had this trait. All three groups must have developed air sacs independently, and each time in a slightly different way.
The air sacs probably increased the oxygen levels in the blood of the dinosaurs. The Triassic period had a scorching hot and dry climate. So more oxygen circulating in the blood would cool the bodies of the dinosaurs more efficiently. It would also allow them to move faster.
The air sacs would have buttressed and reinforced the internal structure of dinosaur bones while creating a greater attachment surface area for large, powerful muscles. This would have allowed the bones to grow to a much larger size without overtaxing the animal.
In live birds, aerated bones reduce overall mass and volume, while improving bone strength and stiffness, essential characteristics for flight.
Paleontology not only tells the story of what Earth might have been like, had it not been for that infamous asteroid, but it also helps us learn about the evolution of creatures still alive.
Echoes of this dinosaur legacy are found in many animals alive today. It’s not just long-dead animals that find this kind of adaptation useful. Many bird species living today rely on hollow bones for flight. Other animals use the air sacs to reinforce and strengthen their large bones and skulls, without overloading them.
An excellent example of this is the elephant skull. Inside elephant skulls are large air sacs that allow the animal to move its massive head and heavy tusks without straining its neck muscles.
The human brain is also protected by two layers of hard, compact bone (internal and external tables) sandwiched by a softer, spongier, airier layer of bone in the middle, known as diploe. This allows our skulls to be lightweight, yet strong and capable of absorbing blows to the skull.
These are examples of convergent evolution in which animals are repeatedly faced with the same problem, developing similar, but not always identical, solutions each time. Today’s animals play by the same evolutionary playbook as dinosaurs.
By Sally Christine Reynolds, Senior Lecturer in Hominin Paleoecology, Bournemouth University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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