One ancient swimming mammal fossil and two evolutionary surprises, including a third set of teeth
What may have looked like a cross between a platypus and a beaverlike rodent and lived around 120 million years ago? Dongoconodon platycauda, a newly discovered fossil mammal from northeastern China. Beyond its unusual features, such as evidence of webbed paddling feet and a rudderlike tail, this semiaquatic mammal had a surprise waiting for scientists in its jaw: a third generation of teeth.
In 2016, a fossil mammal named Dongoconodon platycauda was discovered in the Jiufotang Formation of northeastern China. This ancient creature, which lived around 120 million years ago, possessed unique features that challenged existing scientific assumptions about mammalian evolution. Among its intriguing characteristics were webbed paddling feet, a rudderlike tail, and a surprising third set of teeth.
The fossil, examined through high-resolution CT scans, revealed that this semiaquatic mammal had three generations of teeth, a phenomenon previously thought to evolve early in mammalian history. The discovery of this third tooth generation, along with an ossified cartilage connecting its jaw to its middle ear bones, provided valuable insights into the evolutionary processes that shaped early mammals.
Additionally, the fossil showcased anatomical adaptations suited for a semiaquatic lifestyle, with broad hands and feet featuring flattened finger bones for paddling and a boxlike tail similar to modern nutria. These findings not only highlight the diversity of early mammalian evolution but also suggest that key mammalian traits did not necessarily evolve in a tightly linked fashion.
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