This adaptation allowed the dinosaurs not only to survive, but to dominate the planet: ScienceAlert

It’s sometimes hard to imagine how the planet we call home, with its megalopolis cities and quiet farmlands, was once ruled by dinosaurs the size of buses and five-story buildings.

However, recent research has helped deepen our understanding of why dinosaurs took off: The answer may lie in their specialized bones, textured like aero chocolate.

Brazilian paleontologist Tito Aureliano found that hollow bones filled with small air sacs were so important to dinosaur survival that they evolved independently multiple times in different lineages.

According to the study, aerated bones evolved in three distinct lineages: pterosaurs, technically flying reptiles, and two dinosaur lineages, theropods (ranging from the crow-sized Microraptor to the giant Tyrannosaurus rex) and sauropodomorphs (long-necked herbivores including brachiosaurus).

Researchers focused on the Late Triassic, around 233 million years ago, in southern Brazil.

Every time an animal reproduces, evolution produces random variants in the genetic code. Some of these variants are passed on to offspring and evolve over time.

Charles Darwin believed that evolution created “the most beautiful endless forms”. But some adjustments always come spontaneously, a bit like getting the same hand of cards multiple times.

When the same hand keeps appearing, it’s a sign that evolution has found an important and effective solution.

The variant studied by the Brazilian team was aerated vertebrae, which would have increased the dinosaurs’ strength and reduced their body weight.

Light but powerful

Your regular shipments from Amazon or other online retailers come packaged in corrugated cardboard, which has the same benefits as vented bones. It is lightweight yet sturdy.

Corrugated cardboard, or as it was first called, folded paper, was a man-made design experiment that was hugely successful and is now part of our everyday lives. Patented in England in 1856, it was originally intended to carry top hats then popular in Victorian England and the United States.

Three years later Darwin published his About the origin of species outlining how evolutionary traits that create benefits are more likely to be passed on to future generations than variants that don’t.

CT scanning technology allowed Aureliano and his colleagues to peer inside the rock-hard fossils they were studying. Without modern technology, it would have been impossible to look inside the fossils and see 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 in slightly different ways each time.

The air sacs likely increased the oxygen levels in the dinosaurs’ blood. The Triassic period had a scorching hot and arid climate. So more oxygen circulating in the blood would cool dinosaur bodies more efficiently. It would also allow them to move faster.

The air sacs would have supported and strengthened the inner structure of the dinosaurs’ bones, while providing a greater surface area for attachment for large, powerful muscles.

This would have allowed the bones to grow to a much larger size without weighing the animal down.

In live birds, aerated bones reduce overall mass and volume while improving bone strength and stiffness—essential traits for flight.

Not only does paleontology tell the story of what might have been for Earth if it weren’t for that infamous asteroid, it also helps us learn about the evolution of living creatures.

Prehistoric Connections

Echoes of this dinosaur heritage can be found in many animals alive today. Not only long-dead animals found this type of adaptation useful. Many bird species living today rely on hollow bones to fly.

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 the elephant’s skull are large air sacs that allow 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 plates) sandwiching a layer of softer, spongy and ventilated bone known as the diploe. This makes our skulls light but strong and able to absorb impact to the skull.

These are examples of convergent evolution, where animals are repeatedly presented with the same problem and each time come up with similar—but not always identical—solutions. Animals today play to the same evolutionary playbook as dinosaurs.

Sally Christine Reynolds, Principal Academician in Hominin Palaeoecology, Bournemouth University

This article was republished by The Conversation under a Creative Commons license. Read the original article.