Discovery of Moroccan fossil footprints points to unknown dinosaur diversity

Researchers are hot on the trail of Morocco’s missing dinosaurs.

New research on fossil footprints preserved high in the Atlas Mountains suggests that dinosaurs of all shapes and sizes lived together during the Middle to Late Jurassic around 168 to 160 million years ago. However, skeletal fossils from this period are extremely rare, and are known from just four species including the unusual Spicomellus afer.

The discovery of three new tracksites suggests that there could be many more dinosaurs yet to be discovered in Morocco, and North Africa more widely, opening a new window into a time when dinosaurs were at their peak.

Ahmed Oussou, a PhD student and the study’s lead author, says, ‘So far, fieldwork undertaken in this region has not yet yielded any bones, making it difficult to link the tracks to any given species of dinosaur.’

‘While the quantity of tracks in the area does not necessarily mean that the region is rich in body fossils, I hope that further excavations will allow me and my colleagues to find some bones in the coming years.’

The findings of the study, which was co-authored by Natural History Museum researcher Dr Susannah Maidment, were published in the journal Royal Society Open Science.

How did the Moroccan trackways form?

Dinosaur footprints are an example of a trace fossil. This can include fossilised burrows, tracks, feeding signs as well as preserved faeces, otherwise known as coprolites, and can preserve part of an animal’s behaviour.

While most tracks left by dinosaurs faded away, occasionally they were preserved if made in soft sediments like sand or mud. After being baked hard by the Sun, they were buried by other sediments which formed into rocks like mudstone and sandstone over millions of years.

When the Moroccan tracks were left during the Jurassic, the dinosaurs were walking around ancient wetlands containing many lakes and rivers, thought to be similar to the Okavango Delta in modern-day Botswana. The sediment left behind by these rivers would have been an ideal environment for preserving their footprints.

During the Jurassic, the movement of the African, Eurasian and North American tectonic plates away from each other stretched the Earth’s crust increasingly thin. This caused some parts of the region to sink, while others were forced upwards, including the rocks that would become the Atlas Mountains.

Shortly after the extinction of the dinosaurs 66 million years ago, collisions between the African and Eurasian plates pushed the Atlas Mountain range even higher as the crust was squeezed upwards.

This meant that the once low-lying fossils ended up thousands of metres above sea level as the mountains grew over millions of years. In particular, the region of the Central High Atlas Mountains around the town of Imichil is renowned for preserving a variety of footprints from not just dinosaurs, but also crocodiles and pterosaurs.

While the age of the rocks in this region is not well-known, the researchers uncovered the fossils of shelled animals known as brachiopods. The two species uncovered, Burmirhynchia athiensis and Cymatothynchia reynesi, date to around 165 million years ago.

Which dinosaurs made the tracks?

The three newly uncovered trackways lie between the towns of Imilchil and Outerbat in central Morocco and feature a range of different footprints.

Trackways made by the same species of animal are rarely the same, meaning that they vary significantly depending on what it was walking on, the speed it was moving at, and its age at the time. This means palaeontologists tend to link footprints to general groups of animals rather than any one species.

For instance, the researchers used the general size and shape of the Moroccan footprints at the first tracksite to link them to four key groups of dinosaurs. These included the theropods, a group of carnivores like Tyrannosaurus rex which walked on two legs, as well as sauropods, which are long-necked, large-bodied herbivores which included Diplodocus.

In addition, there appeared to be three thyreophoran tracks, the group of armoured dinosaurs which includes stegosaurs and ankylosaurs, as well as one track from a herbivorous ornithopod.

A separate ornithopod trackway was also found at the second site, along with many small theropod footprints measuring just a couple of centimetres wide. These tracks are the smallest found in the region and potentially the entirety of Morocco, and might suggest a group of dinosaurs moving together in a group.

However, it wasn’t just dinosaurs leaving their mark. The researchers found one footprint with four digits that might have been left by a pterosaur landing in the mud.

Tracksite three, meanwhile, has preserved evidence of ancient burrows, as well as signs of microbes. These were accompanied by a single trackway of bird-like footprints, likely from the animal which made them when wading through deep, soft mud.

Together, the diversity of tracks suggest that many more species of dinosaur were living in North Africa during the Middle Jurassic than are currently known. Further excavations could help to uncover some of these animals, and fill in a gap in our understanding of the prehistoric world.

‘I’m originally from Imilchil, so I'm determined to find out more about the region’s palaeontology,’ Ahmed says. ‘I've already discovered other tracksites that I hope to publish on soon, and I'd like to continue my research in collaboration with other specialists to improve knowledge of Imichil’s past.’