New species of Jurassic crocodile had unusually slender teeth

A new species of ancient crocodile relative that lived around 170 million years ago has been discovered by scientists at the University of Portsmouth and Hassan II University of Casablanca, Morocco.

Unlike most crocodiles, this animal had a long, narrow snout filled with exceptionally thin, needle-like teeth. The teeth were so slender that they are unlike those of any known close relative.

The animal, named Ctenosuchus tenuidens, belonged to a group of marine and freshwater reptiles known as thalattosuchians, which lived during the age of the dinosaurs.

The fossils were found in rocks that were formed in ancient rivers and lakes in what is now the Atlas Mountains of southeastern Morocco.

Hamzah Imran from the University of Portsmouth’s School of the Environment and Life Sciences is 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.’”

Hamzah at his desk with the Ctenosuchus tenuidens fossil

By studying the fossil teeth under powerful microscopes and examining their internal structure, Hamzah and his colleagues found they had specialised ridges and were closely spaced together. These features suggest that Ctenosuchus had a very unusual diet. Rather than hunting large prey, it likely fed on very small fish, crustaceans such as fairy shrimps, and other small aquatic creatures.

Hamzah 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 research helps scientists better understand the diversity and ecology of ancient crocodile relatives that lived in the southern supercontinent Gondwana, which included modern-day Africa.

It also shows that different groups of prehistoric animals evolved similar feeding adaptations independently. The teeth of Ctenosuchus resemble those seen in some ancient aquatic reptiles called mesosaurs, and even certain long-snouted pterosaurs that lived millions of years later.

The scalpel points to the slender teeth of Ctenosuchus tenuidens

In fact, the jaws and teeth of Ctenosuchus have many similarities with the jaws of some Jurassic pterosaur such as Gnathosaurus and Ctenoschama that scientists believe were filter feeders.

Overall, the fossils reveal that Jurassic crocodile relatives occupied a wider range of habitats and feeding roles than previously realised, highlighting the rich prehistoric ecosystems that once existed in Morocco.

Hamzah added: “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.”