Paleontologists have identified the earliest example of a placental mammal in the fossil record to date, which may provide new insights into how our feathered ancestors came to dominate the Earth after the dinosaurs died out.
They made progress by studying the odontological (dental) equivalent of tree rings—the growth lines and elements preserved in fossil teeth—that they used to reconstruct the daily life of one of our first cousins: Pantolambda hamammodon, tall A pig-like creature that escaped about 62 million years ago – shortly after the extinction of the dinosaurs.
He revealed it pantolambda mothers they were pregnant for about seven months before giving birth to a single, well-developed baby, who nursed for only 1-2 months before becoming fully independent.
“I’ve studied dinosaurs for most of my career, but this project on mammal growth is the most exciting research I’ve ever been involved in because I’m amazed that we can identify the chemical fingerprints of birth and weaning in teeth. they are very old,” said Professor Stephen Brusatte of the University of Edinburgh, who participated in the study.
Placental mammals make up the majority of mammal species alive today, from humans to tiny mice to giant whales. They give birth to relatively mature young, most of which they grow up inside their mothers, and are fed through the placenta.
Although mammals existed during the time of the dinosaurs, it wasn’t until their extinction that mammals really began to diversify and grow. One idea is that their ability to give birth to large, well-developed babies that were previously nourished by the placenta was key to their success. This way of growing and reproducing also allows human babies to be born with such large brains.
It is still a mystery when this way of life appeared. Because the bones of early mammals are often small and fragile, there are no fossilized remains of hip bones, for example, that can be used to learn about species’ reproductive styles. The teeth, which paleontologists have long studied to study the lifestyles of extinct mammals, are better preserved.
The new technique is based on this tradition. This involves cutting fossil teeth into extremely thin sections to examine their growth lines and steaming them to understand their chemistry at different stages of development. “It allows us to look at virtually any mammal fossil and reconstruct things like its gestation period, how long it nursed, when it reached adulthood, and how long it lived – things we couldn’t do with fossil mammals before. now,” said Dr Gregory Funston of the University of Edinburgh, who led the study.
case pantolambdaFunston was surprised to discover how advanced this trait was at this point in mammalian evolution.
“One of the closest evolutionary analogs is things like giraffes that are born on the plains, and they have to move in seconds or they’re going to be hunted,” he said. “We would expect these kinds of life histories to emerge slowly and then become more specialized over time, but what we see is that pantolambda, Just 4 million years after its extinction, it is already experimenting with this completely new way of life.
Funston hopes the research could open a new frontier in the study of fossil mammals and their evolutionary path. “This method provides the most detailed window we can hope for into the daily lives of extinct mammals,” he said.