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 ruled the Earth after the dinosaurs went extinct.
They made the breakthrough by examining the odontological (tooth) 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, and burly Dog-pig-like creature that trotted around about 62 million years ago – just after the dinosaurs went extinct.
That turned out to be the case panto lambda mothers They were pregnant for about seven months before giving birth to a single, well-developed baby with a mouth full of teeth who suckled for only 1–2 months before becoming fully independent.
“I’ve studied dinosaurs for most of my career, but this mammalian growth project is the most exciting study I’ve ever participated in as I’m amazed that we were able to take chemical fingerprints from birth and weaning into teeth are so old,” said Prof Stephen Brusatte of the University of Edinburgh, who was involved in the research.
Placental mammals make up the majority of mammal species alive today, from humans to tiny shrews to giant whales. They give birth to relatively mature young that have completed much of their growth inside their mother and are nourished by a placenta.
Although mammals existed since the time of the dinosaurs, it wasn’t until their extinction that mammals began to diversify and grow large. One idea is that her ability to deliver large, well-developed babies previously nurtured by a placenta was key to her success. This style of growth and reproduction also allows human babies to be born with such large brains.
But when exactly this lifestyle emerged was a mystery. Since the bones of early mammals were small and fragile, fossilized remains, such as hip bones, that allow conclusions to be drawn about the reproductive style of the species are often missing. Better preserved are teeth, the size and shape of which paleontologists have long studied to learn more about the way of life of extinct mammals.
The new technology builds on this tradition. It involves cutting fossil teeth into extremely thin sections to study growth lines and evaporating them to understand their chemistry at different developmental stages. “It allows us to look at virtually any fossil mammal and reconstruct things like its gestation period, how long it suckled, when it reached maturity, and how long it lived — things we really couldn’t do with fossil mammals before now.” , said Dr Gregory Funston of the University of Edinburgh, who led the research.
In case of panto lambdaFunston was surprised to find how advanced this trait seemed to be at this point in mammalian evolution.
“One of the closest analogues in terms of its evolution is things like giraffes, which are born right on the plane and have to move within seconds or else they’ll be hunted,” he said. “We would have expected these types of life stories to emerge slowly and then become more specialized over time, but what we’re seeing is this pantolambda, Only 4 million years after the extinction, this whole new kind of life history is already being experimented with.”
Funston hopes the study could open a new frontier in the study of fossil mammals and their evolution. “This method opens the most detailed window we could hope for into the daily life of extinct mammals,” he said.