Scientists Infer Ancient Mammals Lived More Like Reptiles than Present-day Rodents
Image for representation purpose only.
How did mammals evolve? What did they look like in the early stages? Questions like these have been the focus of many prehistoric studies. Some questions have been clearly answered while some are still, debatable, to say the least.
Scientists concur that the first mammals to walk on Earth co-existed with dinosaurs, around 2000 million years ago. But they may not have looked as expected. A new study performed by scanning fossilised teeth revealed earliest mammals must have lived slower and longer life like a lizard rather than mice or shrews which died within a year.
Previously held belief suggested the earliest mammalian lives were more similar to current rodents. X-rays of Kuehneotherium and Morganucodon teeth fossils revealed they could live as long as 14 years. The study was led by Dr Elis Newham from the University of Bristol.
She suggested that these animals had bigger brains and more advanced behaviour than previously believed. They lived slowly, unlike rodents who are born, mature, breed, and die at a very fast pace. The basis of this study was “growth rings”, these are concentric circles deposited in the tooth sockets. Similar to counting tree-rings to determine a tree’s age, these tooth rings could help reveal the age at which the animal died. The results can be found in the journal Nature Communications.
Dr Pam Gill from the same university came up with the idea to use advanced imaging technology for a purpose like this. She said she got the idea from a colleague and a co-author, who came to her after tooth extraction and wanted to get it X-rayed. They said it can reveal a lot about the life history. “That got me wondering whether we could do the same to learn more about ancient mammals,” she said.
She then proceeded to send the teeth fossil to Dr Ian Corfe from the University of Helsinki and the Geological Survey of Finland. He would test her theory that there would be enough material in the cementum – root and around the socket – to reveal new things about the species using high-powered Synchrotron X-ray radiation.
Corfe was delighted to announce that scans of the fraction of millimetre-thick cementum were so clear that the rings could be counted freely. From there, a 6-year international study began. The two 200-million-year-old specimens Morganucodon and Kuehneotherium were the focus. They were found at the Jurassic rocks in South Wales. According to Corfe, they must have fallen into the holes in the cave rocks where their skeleton and teeth were fossilised.
There were hundreds of species in this study and they all led to this conclusion – ancient mammals resembled reptiles in their lifestyle.