The Crocodile That Could Not Bite Hard

There is a particular kind of discovery that arrives not with a roar but with a whisper—a detail so small that it nearly escapes notice, yet it rewrites what we thought we knew. In a fossil from the Atlas Mountains of southeastern Morocco, researchers noticed tiny black circles on either side of a long bone. They could have been mineral stains, geological artifacts, nothing at all. But when Hamzah Imran of the University of Portsmouth put the specimen under a microscope and carefully scratched around one of the circles with a scalpel, it grew longer and longer. They were teeth—dozens of them, slender as needles, arranged like the teeth of a comb .

The animal, named Ctenosuchus tenuidens, lived approximately 170 million years ago during the Jurassic period. It belonged to a group of marine and freshwater reptiles called thalattosuchians, ancient crocodile relatives that lived alongside the dinosaurs . The fossils were found in rocks formed in ancient rivers and lakes, in what is now the Atlas Mountains. The name tells the story: "cteno" means comb, "suchus" means crocodile, and "tenuidens" means thin teeth .

What makes Ctenosuchus remarkable is not merely its anatomy but what that anatomy implies about its behavior. Its teeth were so fine that Imran and his colleagues believe it could not have caught normal prey. "If it caught a big fish, and the fish wriggled, those delicate teeth would get smashed," Imran explained. The team concluded that the animal likely fed on soft prey—shrimp, worms, and tiny fish, nothing that would break its teeth .

This feeding strategy sets Ctenosuchus apart from other long-snouted crocodiles. The teeth had specialized ridges and were closely spaced, features that suggest a filter-feeding or sieving mechanism. The researchers noted that the jaws and teeth of Ctenosuchus resemble those of some Jurassic pterosaurs, such as Gnathosaurus and Ctenochasma, which are believed to have been filter feeders . It is a striking example of convergent evolution—different lineages arriving independently at similar solutions to similar problems.

The discovery also helps scientists understand the diversity of ancient crocodile relatives that lived in Gondwana, the southern supercontinent that included modern-day Africa. The fossils reveal that Jurassic crocodile relatives occupied a wider range of habitats and feeding roles than previously realized . "It just shows there is much more out there that needs to be explored," Imran said. "Morocco has an incredibly rich fossil history, but there is still so much waiting to be discovered" .

For paleontologists, the find is a reminder that the fossil record is not merely a catalogue of large, dramatic creatures. Sometimes the most revealing discoveries are the smallest ones—a row of needle-thin teeth, preserved in stone for 170 million years, telling the story of a crocodile that ate like a whale.

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Sources:

· University of Portsmouth · Journal of Vertebrate Paleontology · Phys.org