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Joschua Knüppe

Saber-toothed anchovies roamed the oceans 45 million years ago

When dinosaurs and other large predators went extinct some 66 million years ago, lots of creatures evolved to take their place. But unlike the plankton-hunting anchovies we eat in Caesar salads today, some ancient anchovies evolved into fish-eating predators, according to a new study.

Researchers examined a 30-centimeter-long fossil embedded in a rock formation near Chièvres, Belgium, and another partial fossil from Pakistan’s Punjab province. They were between 41 million and 54 million years old, and both shared a peculiar feature: a single saber tooth on the upper jaw.

To get high-resolution images of the fish skulls, the researchers used microcomputed tomography—a scaled-down version of the technique doctors use to scan your body in the hospital. The images revealed rows of fangs on the fishes’ lower jaws and a pointy saber tooth on the upper jaw. The fossil from Pakistan was a new species, and researchers named it Monosmilus chureloides after the churel—a shapeshifting creature with sharp fangs that features in many South Asian legends.

Both specimens are close cousins of today’s anchovies, the researchers say. But unlike their docile relatives, these ancient anchovies likely used their fangs to snag their prey (above), the researchers write today in Royal Society Open Science.

This unexpected discovery highlights the extraordinary evolutionary tinkering that followed the end-Cretaceous extinction event, the researchers say, with saber-toothed anchovies living alongside familiar fish groups that inhabit today’s oceans.