Fossil mammal with reptile-like teeth changes picture of our evolution — SkimNews
Get the Health newsletter
Daily health & science — research, biotech, public health, the studies worth knowing. Free.
- Dongoconodon platycauda, a 120-million-year-old fossil found in 2018 in Liaoning, China, weighed up to 190 grams and measured about 40 cm long, with a streamlined body resembling a modern nutria.
- Shundong Bi at Yunnan University and colleagues determined the mammal had broad, webbed hands and feet "remarkably like" a modern platypus, with a flattened tail acting as a rudder for swimming.
- The fossil challenges the century-old textbook view of mammalian diphyodonty — Dongoconodon exhibited polyphyodonty (multiple tooth replacement) across all four tooth classes, a pattern previously associated only with reptiles.
- The specimen preserves one of the most complete middle-ear regions from an Early Cretaceous mammal, including Meckel's cartilage at an intermediate stage where it still made slight contact with the lower jaw.
- The researchers conclude teeth and ear bones evolved independently rather than as a tightly linked suite, with Bi calling early mammalian evolution "considerably more flexible than the traditional textbook picture suggests."
- Mike Benton at the University of Bristol called the find an "interesting, quite late-occurring mammal" that retained hints of reptilian ancestry long after other Mesozoic mammals had made those transitions by the end of the Triassic.
Why it matters: The finding forces a rewrite of the model that tooth replacement and middle-ear evolution were tightly linked in early mammals — any biology curriculum still teaching strict diphyodonty as a defining mammalian trait now has a 120-million-year-old counterexample. Researchers cataloguing Mesozoic mammal diversity gain evidence that these traits evolved independently, expanding the range of evolutionary experiments during the age of dinosaurs.
Ask SkimNews
