Spicomellus afer isn’t just a super spiky anklyosaur. It’s the oldest known ankylosaur to ever wield a tail weapon. An examination of a new Spicomellus afer specimen published in the journal Nature indicates the Middle Jurassic herbivore also featured a unique collar of three-foot-long horns, as well as a tail weapon 30 million years before any of its other anklyosaur relatives.
“We’ve never seen anything like this in any animal before,” study co-author and paleontologist Susannah Maidment said in a statement.
Although Spicomellus lived around 165 million years ago, the vast majority of its ankylosaurid descendants existed about 74 to 67 million years ago during the late Cretaceous. These stout dinosaurs are particularly recognizable due to their distinctive armored plating and defensive horns that covered large portions of their bodies. Many species also evolved specialized tails equipped with their own spikes or club-like protrusions that they wielded with often deadly results.Â
Spicomellus was first described in 2021, but it was only based on a single rib bone. However, a farmer’s discovery near the Moroccan town of Boulemane in 2022 revealed a far more complete example of the small dinosaur. After months of subsequent excavation work and laboratory analysis, Maidment and her teammates were stunned by what they found.
“Spicomellus had a diversity of plates and spikes extending from all over its body, including meter-long [3.3-foot-long] neck spikes,” said Maidment.
The dinosaur also featured large, upward-growing spikes over its hips, an array of blade-like spikes down its torso, and armor plates across its shoulders. A series of bony spikes fused to and projecting from its ribs is also completely unique to this species. Many of these deadly accessories continued growing throughout the dinosaur’s life.
“To find such elaborate armor in an early ankylosaur changes our understanding of how these dinosaurs evolved,” Maidment explained. “It shows just how significant Africa’s dinosaurs are, and how important it is to improve our understanding of them.”
Further setting Spicomellus apart from other creatures is its tail weapon. Although common to anklyosaurs by the Early Cretaceous, the defensive tool had never been seen that far back in the dinosaur family’s lineage. This second specimen didn’t include the end of its tail, but a fused vertebrae structure known as a handle strongly supports the existence of some form of club or spiked tail-topper.
Study co-author Richard Butler described the team’s discoveries as “spine-tingling.”
“We just couldn’t believe how weird it was and how unlike any other dinosaur, or indeed any other animal we know of, alive or extinct,” he added.
Maidment, Butler, and their other collaborators theorize that the spikes both protected Spicomellus against predators and rivals, as well as attracted potential mates. Some of the armor also appears more decorative than defensive, which is missing from all other known anklyosaurs. One potential explanation is that as predators evolved larger into the Cretaceous, ankylosaur armor evolved along with them to become simpler and more utilitarian.
“It turns much of what we thought we knew about ankylosaurs and their evolution on its head and demonstrates just how much there still is to learn about dinosaurs,” said Butler.
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