Scientists studying 170-million-year-old fossils from Morocco spotted tiny black circles under a microscope; scraping revealed needle-thin teeth from a new crocodile relative that likely ate shrimp and small fish

Published in the Journal of Vertebrate Paleontology, the research adds to scientists’ understanding of the ecosystems that existed in Gondwana, the ancient southern supercontinent that included much of modern-day Africa.

Sometimes a major scientific discovery starts with something barely visible. Researchers studying Moroccan fossils found tiny black circles along a long bone. Under a microscope, these markings revealed an unexpected secret: an array of exceptionally slender teeth belonging to a previously unknown crocodile relative that lived around 170 million years ago. The discovery offers a glimpse into the surprising diversity of prehistoric predators during the Jurassic Period, states a release by the University of Portsmouth.

A closer look reveals a new species

The species, named Ctenosuchus tenuidens, was identified by researchers from the University of Portsmouth in the UK and Hassan II University of Casablanca in Morocco. It belonged to the thalattosuchians, a group of ancient reptiles related to crocodiles that occupied marine and freshwater environments during the age of the dinosaurs.Unlike modern crocodiles, which typically have robust teeth suited to gripping prey, this animal had a long, narrow snout lined with needle-like teeth so fine that they stood out from those of its known relatives. The fossils were recovered from rocks formed in ancient rivers and lakes in what is now the Atlas Mountains of southeastern Morocco. The discovery began when researchers examined the unusual dark markings on one of the specimens more closely. Carefully scraping the surrounding material exposed elongated structures that turned out to be teeth.Special anatomy is reflected in the name. Cteno refers to a comb, suchus means crocodile, and tenuidens translates to thin teeth, a fitting description of the animal’s closely spaced dental arrangement.

A different-diet predator

Teeth shape and structure revealed Ctenosuchus tenuidens’ lifestyle. Using powerful microscopes, researchers examined the teeth’s internal features and identified specialised ridges and a tightly packed arrangement.These characteristics suggest that the animal was adapted to feeding on small, relatively soft aquatic prey rather than pursuing larger fish. Its likely diet included tiny fish, crustaceans such as fairy shrimp, worms and other small water-dwelling creatures. The delicate teeth would probably have been poorly suited to gripping struggling, larger prey, which could have damaged them. Instead, the animal appears to have occupied a specialised feeding niche, setting it apart from other long-snouted crocodile relatives.

Evolution repeats its experiments

The discovery also highlights a recurring pattern in evolution: unrelated groups of animals can develop similar features when adapting to comparable food sources. The teeth and jaws of Ctenosuchus tenuidens resemble those of certain ancient aquatic reptiles called mesosaurs, as well as some long-snouted pterosaurs, including Gnathosaurus and Ctenochasma. These flying reptiles lived during the Jurassic and are believed to have used specialised jaws for filter feeding. Such similarities suggest that different prehistoric animals independently evolved comparable feeding adaptations, demonstrating how a shared ecological challenge can produce similar anatomical solutions.

Morocco’s prehistoric secrets

Published in the Journal of Vertebrate Paleontology, the research adds to scientists’ understanding of the ecosystems that existed in Gondwana, the ancient southern supercontinent that included much of modern-day Africa. It also challenges the familiar image of crocodile relatives as predators built primarily to capture large prey. During the Jurassic, these animals occupied a broader range of habitats and ecological roles than their modern descendants might suggest The fossils from Morocco reveal how much remains to be learned from rocks that have preserved traces of life for millions of years.Images Courtesy: istock and University of Portsmouth