Ammonites Thrived Before Dinosaur-Killing Asteroid Impact, Study Finds

New research challenges the previous understanding of ammonite extinction. These coiled-shell creatures, relatives of squid and octopus, were previously thought to be in decline before they vanished alongside dinosaurs 66 million years ago.

A study published in Nature Communications by palaeontologists at the University of Bristol suggests a different story. Ammonites, it appears, were flourishing right up until the cataclysmic asteroid impact that wiped out the dinosaurs.

This finding overturns a long-held belief and sheds new light on the event that dramatically altered Earth's biodiversity. Dr Joseph Flannery-Sutherland, the lead author, highlights the importance of reevaluating the fossil record, acknowledging its limitations in portraying the complete picture of past ecosystems.

"Ammonites had an amazing evolutionary history. With their formidable shells and powerful tentacles, they innovated the act of swimming. They could grow to as big as a car or to just a few millimetres in diameter. They played equally disparate roles in their ecosystems, from predators near the top of the food web to filter feeding off plankton," said Dr Austin Hendy, Curator of Invertebrate Palaeontology at the Natural History Museum of Los Angeles County.

"Understanding how and why biodiversity has changed through time is very challenging," said lead author Dr. Joseph Flannery-Sutherland. "The fossil record tells us some of the story, but it is often an unreliable narrator. Patterns of diversity can just reflect patterns of sampling, essentially where and when we have found new fossil species, rather than actual biological history. Analysing the existing Late Cretaceous ammonite fossil record as though it were the complete global story is probably why previous researchers have thought they were in long-term ecological decline."