Paleontologists have identified the first example of a placental mammal in the fossil record so far, which could provide new insights into how our ancestors took control of Earth after the extinction of the dinosaurs.
They achieved this breakthrough by studying the dental equation (teeth) for tree rings—the growth lines and elements preserved in fossil teeth—which they used to reconstruct the daily life of one of our early cousins: Pantulamda BathmodonAnd the fat A pig-like creature with dogs, it trotted about 62 million years ago – shortly after the extinction of the dinosaurs.
Doing so revealed it pantolambda mothers She was about seven months pregnant, before giving birth to one well-developed baby, with full mouthful teeth, and breastfed for only one to two months before becoming fully independent.
“I have studied dinosaurs for most of my career, but this project on mammalian development is the most exciting study I have ever been involved in, as it surprised me that we were able to identify the chemical fingerprints of birth and weaning in teeth,” said Professor Stephen Brusatte of the University of Edinburgh, who was involved in the research, “They are very old.”
Placental mammals represent the majority of mammal species alive today, from humans, to small shrews, to giant whales. They give birth to relatively mature young, which did much of their growth within their mothers, and fed through the placenta.
Although mammals existed in the time of the dinosaurs, mammals began to diversify and grow exponentially until the latter became extinct. One idea is that their ability to deliver large, well-developed babies previously nourished by the placenta has been key to their success. This pattern of growth and reproduction is also what enables children to be born with such big brains.
However, exactly when this lifestyle appeared was a mystery. Because the bones of early mammals were small and fragile, fossilized remains of hip bones, for example, that could be used to derive insights into the species’ reproductive patterns, are often lacking. The teeth are best preserved, the size and shape of which have long been studied by paleontologists to learn about the lifestyles of extinct mammals.
The new technology builds on this tradition. It involves cutting fossil teeth into very thin sections to examine growth lines and steaming them to understand their chemical composition at different stages of development. “It allows us to look at virtually any fossil mammal and reconstruct things like how long they are pregnant, how long they lactate, when they reach maturity, how long they last – things we haven’t really been able to do in fossil mammals before now,” said Dr. Gregory Vanstone of the University of Edinburgh, who led the research.
in case if pantolambdaFunston was surprised to discover how advanced this trait is at this point in mammalian evolution.
“One of the closest analogues in terms of evolution are things like giraffes, which are born directly on the plains, and have to move within seconds or else they will be hunted,” he said. “We were expecting these types of life history to have arisen slowly, and then become more specialized over time, but what we’re seeing is pantolambda, Only 4 million years after the extinction, we are already trying this completely new way of dating life.”
Funston hopes the study will open new avenues for research into fossil mammals, and how they evolved. “This method opens the most detailed window we can hope for in the everyday lives of extinct mammals,” he said.
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