Fossilized teeth help scientists unlock the secrets of mammals Paleontology

Paleontologists have identified the earliest example of a placental mammal in the fossil record to date, which could provide new insights into how our furry ancestors came to dominate the Earth after the dinosaurs went extinct.

They made the discovery by studying the odontological (dental) equivalent of tree rings—growth lines and elements preserved in fossil teeth—which they used to reconstruct the daily life of one of our early cousins: Pantolambda bathmodon, a big body pig-like creature that evolved about 62 million years ago – shortly after the extinction of the dinosaurs.

Doing so revealed that pantolambda mothers were pregnant for about seven months before giving birth to a single, well-developed baby with a mouthful of teeth that sucked for only 1-2 months before becoming fully independent.

“I’ve spent most of my career studying dinosaurs, but this project on mammal growth is the most exciting study I’ve ever been a part of, as I’m amazed that we were able to identify chemical traces of birth toes and teeth. . are so old,” said Professor Stephen Brusatte at the University of Edinburgh, who was involved in the research.

Placental mammals make up most of the mammal species alive today, from humans, to small cubs, to giant whales. They give birth to relatively mature young that have done most of their growth inside their mother, nourished through a placenta.

Although mammals existed during the time of the dinosaurs, mammals really only began to diversify and grow until they became extinct. One idea is that their ability to give birth to large, well-developed babies that had previously been nourished by a placenta was key to their success. This style of growth and reproduction is also what enables human babies to be born with such large brains.

However, exactly when this lifestyle appeared has been a mystery. Because the bones of early mammals were small and fragile, fossilized remains of, for example, hip bones that could be used to glean insights into species’ reproductive styles are often missing. Better preserved teeth, the size and shape of which paleontologists have long studied to learn about the way of life of extinct mammals.

The new technique is based on this tradition. It involves cutting fossil teeth into extremely thin sections to examine growth lines and evaporating them to understand their chemistry at different stages of development. “It allows us to look at almost any fossil mammal and reconstruct things like its gestation period, how long it nursed, when it reached maturity and how long it lived – things that we really haven’t been able to do in fossil mammals. before. now,” said Dr Gregory Funston at the University of Edinburgh, who led the research.

In the case of pantolambdaFunston was surprised to find how advanced this trait seemed at this point in mammalian evolution.

“One of the closest analogues in terms of its development is things like giraffes, which are born right on the plains, and they have to move within seconds or they’ll be hunted,” he said. “We would expect that these types of life histories would have arisen slowly, and then become increasingly specialized over time, but what we’re seeing is that pantolambda, just 4 million years after the extinction, it’s already experimenting with this whole new way of life history.”

Funston hopes the study could open a new frontier in research into fossil mammals and how they evolved. “This method opens up the most detailed window we could hope for into the daily lives of extinct mammals,” he said.

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