Many of Spicomellus’s bones are covered in spikes, which may have played roles in defence and display. © Matthew Dempsey
By James Ashworth
The world’s most unusual dinosaur is even stranger than first realised.
While the bones of Spicomellus afer were already unlike any known animal, newly discovered fossils have revealed that its entire skeleton was covered in extraordinary bone spikes measuring up to a metre long.
An incredible dinosaur from Morocco reveals that the extensive defences of the ankylosaurs evolved much earlier than first thought.
Back in 2019, our palaeontologist Professor Susannah Maidment acquired an extraordinary dinosaur rib bone from a fossil dealer in Cambridge. The bone had protective spines that were fused directly to its surface, something which had never been seen before in the animal kingdom.
Susannah and her team named this astonishing dinosaur Spicomellus afer, and were keen to find out more about it. However, while the fossil was known to have entered the commercial fossil trade after being found near the town of Boulemane, Morocco, its exact origins were uncertain.
To find more of Spicomellus’s fascinating fossils, Susannah had to turn detective.
After the species was named in 2021, more fossils from Spicomellus were uncovered in a dig in 2023. © The Trustees of the Natural History Museum, London
This eventually led a team of British, American and Moroccan palaeontologists to mount an expedition to the region to search for more of Spicomellus’s remains. They came away with much more of the skeleton than they could have hoped for, revealing that the dinosaur’s entire body was covered in spikes.
As well as its spiked ribs, Spicomellus had huge spikes projecting out of its hips, a tail weapon, blade-like bones running down its sides and a bony collar ringed with spikes. The longest are believed to have been more than a metre long, sticking out from either side of its neck.
What makes this all the more astounding is that, at 165 million years old, Spicomellus is the oldest known ankylosaur. Susannah says that its “absolutely bizarre” fossils are changing how scientists think these armoured dinosaurs evolved.
Hear more about Spicomellus from the scientists who discovered its fossils.
“When we originally named Spicomellus, there were doubts that it was an ankylosaur at all,” recalls Susannah. “Now, not only can we confirm beyond a doubt that this interpretation was correct, but Africa’s only known ankylosaur is far weirder than anyone imagined.”
“To find such elaborate armour in an early ankylosaur changes our understanding of how these dinosaurs evolved. It shows just how significant Africa’s dinosaurs are, and how important it is to improve our understanding of them.”
The University of Birmingham’s Professor Richard Butler, who co-led the new Spicomellus paper, adds that the newly described fossils are “an incredibly significant discovery”.
“Spicomellus is one of the strangest dinosaurs that we’ve ever discovered,” Richard says. “It’s utterly unlike any other found anywhere else in the world.”
“I think it's going to really capture the imagination of people around the world, and tell us a lot about the early evolution of the tank-like ankylosaurs.”
The findings of the study were published in the journal Nature.
The discovery of new Spicomellus fossils has allowed palaeontologists to reconstruct what the dinosaur might have looked like. © Matthew Dempsey/ Maidment et al.
The most unusual feature of Spicomellus are the characteristics that gave the dinosaur its name – its spikes. While these structures aren’t that unusual in living or extinct reptiles, they’re usually embedded in the skin. Many of Spicomellus’ spikes, however, are fused to its bones.
“This is completely unlike any animal living or dead, and raises real questions about how this animal moved,” Susannah explains. “Normally, bones like the ribs are used for muscle attachment, but because of the spikes it’s hard to tell where the muscles could have gone.”
“Frankly, we have very little idea about how this dinosaur would have moved at all.”
With spikes embedded in many of its bones, it’s difficult to imagine how Spicomellus might have moved. © The Trustees of the Natural History Museum, London
The largest spikes on the dinosaur measure a whopping 87 centimetres long and emerge from a bone collar that sat around its neck. When the animal was alive, however, they would probably have been even longer. The researchers think they were covered by a keratin sheath similar to the horns of cows.
“This collar of spikes would have been one of several around Spicomellus’ neck,” says Susannah. “While other ankylosaurs have cervical collars made out of a ring of bony plates, there’s nothing quite like this.”
“It’s particularly strange, because this is the oldest known ankylosaur. We might expect that some later species might have inherited similar features, but they haven’t.”
Tail clubs, like this example from Euoplocephalus, have been found in Cretaceous ankylosaurs, but Spicomellus’s tail weapon is the earliest known so far. © The Trustees of the Natural History Museum, London
Another confusing aspect of the dinosaur is its tail. While the end of Spicomellus’ tail hasn’t been found, the bones that do survive suggest that it ended in a club or a similar weapon.
This is unexpected because it has historically been thought that this sort of weaponry only evolved in later species. The newly found fossils challenge that assumption.
“Some of the tail vertebrae are fused together to form a structure known as a handle, which has only been found in ankylosaurs with a tail club,” Susannah says. “However, all these animals lived millions of years later in the Cretaceous.”
“The combination of a tail weapon and a sacral shield, armour plates which protect the hips, suggest that many of the ankylosaurs’ key adaptations already existed by the time of Spicomellus.”
The blade-like bones are believed to have lined the dinosaur’s sides. © The Trustees of the Natural History Museum, London
In nature, highly exaggerated features of an animal are often caused by sexual selection. These include, for example, the tail feathers of a male peacock or the antlers of a stag. Susannah and her colleagues suspect that this might have also been the case with Spicomellus’s elaborate armour.
“It would have been very energetically expensive to produce and carry around such extraordinary armour, and probably limited how well Spicomellus could move,” explains Susannah.
“So, we think that it was probably using its armour for some kind of display. We speculate that the armour evolved first for defence and was later co-opted for attracting mates and showing off to rivals.”
Smaller spikes were embedded in Spicomellus’s armour plating. © The Trustees of the Natural History Museum, London
So far, such extravagant armour is unique to Spicomellus. The armour of later ankylosaurs is much more functional and was seemingly used only for defence.
One possible explanation for this is that larger predators were evolving. A rising risk of predation could have driven ankylosaur armour to become simpler and more defensive as the energetic cost of elaborate display structures became too much.
Another possibility is that ankylosaurs could have moved from visual displays to win mates to combat. Complex armour would have been a burden during these battles, which may have driven the evolution of simpler forms.
Research into Spicomellus has been an international collaboration between researchers like Professor Driss Ouarhache (left) and Professor Susannah Maidment (right). © The Trustees of the Natural History Museum, London
The team hope that ongoing research into the region’s fossils could help narrow down an explanation and offer further insights into Morocco’s Middle Jurassic. Professor Driss Ouarhache, a co-author from the Université Sidi Mohamed Ben Abdellah, says this is helping to drive forward Moroccan science.
“Morocco has a strong background in classical geology, but discoveries like this show the importance of palaeontology as well,” Driss says. “We’ve never seen dinosaurs like this before, and there’s still a lot more this region has to offer.”
“By publishing papers like this, we hope to raise the profile of this country's fossils with more scientists worldwide, and bring them to Morocco to collaborate with us.”
Find out what Museum scientists are revealing about how dinosaurs looked, lived and behaved.
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