The massive asteroid impact 66 million years ago wiped out more than half of all life on Earth, but a new study shows that one species survived longer than previously thought.
Ammonites are an extinct, prehistoric group of cephalopods known for their beautiful coiled shells. They are among the most well-known and iconic fossils in the world.
Until now, it was believed that they went extinct following the asteroid impact 66 million years ago. But new research based on findings from Stevns Klint now shows that ammonites survived for several millennia after the mass extinction.
– This is a major breakthrough in our understanding of the evolution of life on Earth. Fossil textbooks teach us that ammonites went extinct along with the dinosaurs, but thanks to the new discoveries at Stevns Klint, we can now prove that this is not true,” says Jesper Milàn, curator at the KALK Museum in Faxe, which is part of the East Zealand Museums.
Jesper Milàn is part of an international team of researchers who, under the leadership of ammonite expert Professor Marcin Machalski from the Institute of Paleobiology at the Polish Academy of Sciences, have collaborated on the new study.
The Cliff Makes Us Smarter
Stevns Klint is unique because the cliff has preserved a complete geological sequence. At the bottom is the chalk from the Cretaceous Period, followed by the famous layer of fish bones that marks the asteroid impact and the mass extinction of more than half of all life on Earth, and on top of that is the limestone from the Paleogene Period, when the surviving animals evolved into the life we know today on Earth.
The ammonites found at Stevns were discovered in layers lying up to 38 centimeters above the Fiskeleret Formation, which formed 60,000 to 100,000 years after the asteroid impact 66 million years ago—a time when ammonites were traditionally thought to have become extinct.
“It has been an incredibly fascinating study to be a part of, and once again we can be proud that Stevns Klint can help us learn more about the past and the evolution of life,” says Jesper Milàn.
The study has just been published in the prestigious scientific journal *Scientific Communications* (Nature), which was the third most-cited scientific journal worldwide in 2025.
See the study in *Nature*: https://doi.org/10.1038/s41598-025-34479-1
The article is also featured in *Science*: https://www.science.org/content/article/against-all-odds-curious-sea-creature-survived-dino-killing-asteroid