Ancient anchovies were huge and used sabre teeth to eat other fish - New Scientist News

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A sabre-toothed anchovy being caught by an early whale

Huge sabre-toothed anchovies once hunted other fish through the seas. They may have evolved because the asteroid that killed the dinosaurs also wiped out many of the world’s marine predators, providing an opportunity for the metre-long anchovies to take their place.

Alessio Capobianco at the University of Michigan and his colleagues used a technique called micro-computed tomography, similar to the sort of CAT scan you might get at the hospital, to examine two fossilised fishes that lived about 55 million years ago. This allowed them to examine the fossils in more detail than has been possible before.

They found that both fossils – one found in Belgium and the other in Pakistan – bore many similarities to modern anchovies. But there were two surprising differences: each of the fossilised skulls had teeth similar to carnivores with one long sabre tooth at the front of its mouth, and they were both far larger than modern anchovies. One was nearly half a metre long, and the other a full metre.

Anchovies today have tiny teeth that are mainly used to eat plankton, but these early anchovies probably preyed on other fishes. The sabre tooth may have been used to trap other fish in the anchovies’ mouths or to stab prey.

Capobianco says that they may have evolved to become predators because the mass extinction event about 10 million years earlier killed off many of the other marine predators. “After that mass extinction, there was this juxtaposition of very familiar fishes and completely weird offshoots, bizarre evolutionary experiments,” he says.

Figuring out how marine life evolved and adapted around this time period could help us understand how evolutionary processes proceed after a mass extinction event.

It’s not yet clear why these strange toothy anchovies didn’t make it to the present day, but if they had, they wouldn’t be anything like the anchovies we know and eat now. “I would love to know how sabre-toothed anchovies tasted like – they probably would taste different because they ate other fishes instead of plankton,” says Capobianco.

Journal reference: Royal Society Open Science, DOI: 10.1098/rsos.192260