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A team of paleontologists from the Natural History Museum in the U.K., the University of Birmingham, also in the U.K., and Sidi Mohamed Ben Abdellah University, in Morocco, has unearthed the oldest known cerapodan ornithischian dinosaur to date.

In their paper in the journal Royal Society Open Science, the group describes how they were digging at a site in the Middle Atlas Mountains in Morrocco when they uncovered a fossilized upper limb bone, which they recognized as belonging to a cerapodan dinosaur.

Cerapodan dinosaurs were plant eaters and were small compared to other dinosaurs. They hopped around on two legs like modern birds. "Ornithischian" is a term scientists use to describe a type of "bird-hipped" herbivorous dinosaur.

Prior research has shown that they were plentiful during the Cretaceous across the globe, but our knowledge of their history prior to that, during the Middle Jurassic, has been sketchy at best, due to a lack of rocks from that period in which to look for fossils.

The fossil uncovered by the team, a femur, had all the earmarks of a cerapodan; a groove on the back of the top of the femur and the shape of the head itself was distinct, uniquely cerapodan. The team has dated the fossil to approximately 168 million years ago, beating the previous record-holder, an iguanodontian femur found in England, by approximately 2 million years.

It was found, the team notes, in a bed of Bathonian rock, in the El Mers III Formation near a dig site that had previously yielded the world's oldest ankylosaur.

The researchers note that the fossilized femur has confirmed theories that have suggested that cerapodan dinosaurs had diversified prior to the Cretaceous, which no doubt led to their ability to survive in so many different types of climates.

The finding is expected to shed more light on the evolution of cerapodans—most of the prior evidence of their existence has been fossilized trackways. Finding a body fossil, the team suggests, is likely to fill in a lot of gaps. They note that the finding hints at the possibility of more cerapodan fossils waiting in the Middle Atlas Mountains for researchers to find them.

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