Earlier existence of diaphragm confirmed
1 Dec 2016 by Evoluted New Media
Researchers have discovered evidence of diaphragms in mammal-like reptiles that lived 250-300 million years ago, confirming this muscle is older than was previously thought.
Caseids – animals that lived during the Carboniferous and Permian period - possessed a barrel shaped trunk and joints that would have affected rib motility, reducing the amount of air they could inhale. Scientists researching their bone structure inferred that they must have been aquatic animals as their bones were sponge-like, similar to whales.
The research group carried out a number of calculations to see if caseids would have been able to resurface and breathe deeply to fill their lungs with air without a diaphragm. Their physiology would have meant they would have only been able to fill about half of their lung capacity – not ideal for an aquatic animal. Because of this the scientists believe they would have had diaphragms.
Dr Christen Shelton, from Bonn University and co-author, said: “The bone structure totally surprised me. Suddenly, the barrel-shaped trunk with the short neck made sense. The paddle-like extremities were used for swimming.”
The bone structure that scientists discovered was spongy, similar to how bones of osteoporosis sufferers look. Thinking this was linked to the age of the specimen they examined a younger specimen before realising it was common in all caseids.
The scientists concluded that the least common ancestor of caseids and mammals had a diaphragm more than 200 million years ago – 50 million years earlier than previously assumed. This find will result in a re-evaluation of how warm blooded animals evolved - the respiratory system is closely linked with the evolution of warm blooded animals.
Dr Lambertz, also from the University of Bonn and another co-author, said: “Evolution has brought up some weird animals, such as the caseids. We still don’t know that much about these animals. It has been a long way towards mammals, but the origin of the diaphragm marked a turning point on it.”
The research was published in Annals of the New York Academy of Sciences.
