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British scientists have discovered a new species of crocodile that roamed the Earth 170 million years ago.
Its teeth were so thin they resembled toothpicks, with the team behind the discovery saying that they were so slender the crocodile could have hunted only small fish and nothing larger.
The species has been named Ctenosuchus tenuidens, a nod to teeth resembling a fine hair comb.
The discovery was made by researchers at the University of Portsmouth and Hassan II University of Casablanca in Morocco.
They say that Ctenosuchus tenuidens belonged to a group of marine and freshwater reptiles known as thalattosuchians.
The fossils came from rocks formed in ancient rivers and lakes in what is now the Atlas Mountains of southeastern Morocco.
Hamzah Imrah, from the University of Portsmouth’s School of the Environment and Life Sciences, was the lead author of the research.
He said: “We noticed these little black circles on either side of the long bone in the middle of one of the fossils, so we put it under a microscope.
“We carefully scratched around one of the black circles with a scalpel, and as we uncovered more of it, it became longer and longer.
“That’s when we realised these little black circles were actually incredibly thin teeth.
“These comb-like teeth inspired the name Ctenosuchus tenuidens as ‘cteno’ means ‘comb,’ ‘suchus’ means ‘crocodile,’ and ‘tenuidens’ means ‘thin teeth.’”
By studying the fossil teeth under powerful microscopes and examining their internal structure, the researchers found specialised ridges that were closely spaced together.
This suggests that the crocodile had a very unusual diet.
It likely fed on very small fish, crustaceans such as fairy shrimps, and other small aquatic creatures rather than hunting large prey.
Mr Imrah said: “The teeth are so fine that we don’t think it was catching normal prey. If it caught a big fish, and the fish wriggled, those delicate teeth would get smashed.
“We think the animal was probably eating soft prey like shrimp, worms and tiny fish, so nothing that would break its teeth.
“These feeding habits make this particular species very different to other long-snouted crocodiles, so it really is quite an exciting discovery!”
The teeth of Ctenosuchus resemble those seen in some ancient aquatic reptiles called mesosaurs, an extinct genus of aquatic reptile.
They also resemble certain long-snouted pterosaurs that lived millions of years later.
The jaws and teeth of Ctenosuchus share many similarities with the jaws of some Jurassic pterosaurs such as Gnathosaurus and Ctenoschama, which scientists believe were filter feeders.
The research shows that different groups of prehistoric animals evolved similar feeding adaptations independently.
It also helps scientists better understand the diversity and ecology of ancient crocodile relatives that lived in the southern supercontinent Gondwana.
Overall, the fossils reveal that Jurassic crocodile relatives occupied a wider range of habitats and feeding roles than previously realised.
They highlight the rich prehistoric ecosystems that once existed in Morocco.
Mr Imrah concluded: “It just shows there is much more out there that needs to be explored. Morocco has an incredibly rich fossil history, but there is still so much waiting to be discovered.”