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 found that hollow bones filled with small air sacs were so important to the survival of dinosaurs that they evolved independently several times in different lineages.
According to the study, aerated bones evolved in three separate lineages: pterosaurs, technically flying reptiles, and two dinosaur genera, theropods (ranging from the crow-sized Microraptor to the enormous Tyrannosaurus rex) and sauropodomorphs (long-necked herbivores including Brachiosaurus).
The researchers focused on the late Triassic period, about 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 “endless forms, the most beautiful”. But some adaptations appear spontaneously time and time again, a bit like being dealt the same hand of cards on several occasions.
When the same hand keeps appearing, it is a sign that evolution has hit on an important and effective solution.
The variant the Brazilian team studied was vented vertebrae, which would have improved the dinosaurs’ strength and reduced their body weight.
Light but mighty
Your regular deliveries from Amazon or other online retailers come packed in corrugated cardboard, which has the same benefits as airy bones. It is light, yet tough.
Corrugated cardboard, or as it was first known, pleated paper, was a man-made design experiment that was very successful and is now part of our everyday life. Patented in England in 1856, it was originally designed to support top hats, which were popular in Victorian England and the United States at the time.
Three years later, Darwin published his On the origin of species who outlined 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 into the rock-hard fossils they were studying. Without modern technology, it would have been impossible to look into the fossils and discover the air sacs in the spine.
The study found that no common ancestor had this trait. All three groups must have developed air sacs independently, and each time in slightly different ways.
The air sacs probably increased the oxygen levels in the dinosaurs’ blood. The Triassic period had a scorching hot and dry climate. So more oxygen circulating in the blood would cool the dinosaurs’ bodies more effectively. It would also allow them to move faster.
The air sacs would have supported and reinforced the internal structure of the dinosaurs’ bones, while also creating a greater surface area of attachment for large, powerful muscles.
This would have allowed the bones to grow to a much larger size without weighing the animal down.
In living birds, aerated bones reduce overall mass and volume while improving bone strength and stiffness—essential properties for flight.
Paleontology not only tells the story of what might have been for Earth had it not been for the infamous asteroid, but also helps us learn about the evolution of still living creatures.
Echoes of this dinosaur heritage are found in many animals living today. It’s not just long-dead animals that found this type of adaptation useful. Many species of birds alive today rely on hollow bones for flight.
Other animals use the air sacs to support and strengthen their large bones and skulls without weighing them down.
An excellent example of this is the elephant skull. Inside elephant skulls are large air sacs, which enable the animal to move its massive head and heavy tusks without straining the neck muscles.
The human brain is also protected by two layers of hard, compact bone (inner and outer tables), which embed a layer of softer, spongy, aerated bone in between, known as diploe. This allows our skulls to be light but strong and able to absorb shock to the skull.
These are examples of convergent evolution, where animals repeatedly face the same problem and each time develop similar – but not always identical – solutions. Animals today play by the same evolutionary playbook as the dinosaurs.
Sally Christine Reynolds, Senior Academic in Hominin Palaeoecology, Bournemouth University
This article is republished from The Conversation under a Creative Commons license. Read the original article.