A new partial skeleton from Morocco’s Middle Atlas Mountains reveals the world’s oldest ankylosaur, with spikes fused directly to its ribs and an elaborate neck armor featuring spikes up to 87 centimeters long.
This Middle Jurassic dinosaur, Spicomellus afer, challenges long-held ideas about how these armored herbivores evolved their defenses. The analysis, published August 27 in Nature, confirms the ankylosaur identity of Spicomellus and highlights its unique dermal armor, including a tail weapon that appeared millions of years earlier than expected. The specimen includes vertebrae, ribs, hip bones, and a variety of osteoderms, offering the first detailed look at early ankylosaur anatomy from a time when their fossil record is otherwise scarce.
“No other vertebrate possesses the exceptionally elaborate dermal armour of Spicomellus,” the researchers note in the study.
Ankylosaurs were quadrupedal plant-eaters covered in bony plates and spikes, thriving mainly in the Northern Hemisphere during the Cretaceous period. But their origins in the Early to Middle Jurassic remain poorly understood, with only scattered remains like jaws and teeth from places such as the UK. Recent finds from southern continents, including Antarctica and Australia, have hinted at greater diversity, but Spicomellus stands out as the first from Africa and the oldest globally.
The fossil was excavated from the Bathonian-aged El Mers III Formation, a floodplain deposit near Boulemane. Discovered by a local farmer and further documented by scientists, the bones show no signs of duplication and match in size, indicating they belong to one individual. The environment preserved the skeleton well, allowing for a detailed study of its bizarre features.
Reconstruction by Matt Dempsey
To examine the specimen, the team used high-resolution imaging and anatomical comparisons with other ankylosaurs. They found that all dorsal ribs have spikes fused to their upper surfaces, forming a flat base with rounded projections — up to six per rib in some cases. This fusion is unprecedented, differing from other armored dinosaurs where spikes typically attach to skin or sit separately.
The neck armor, or cervical half-ring, consists of a basal band with massive flattened spikes on each side, flanked by smaller ones, creating a horseshoe shape. Other osteoderms include blade-like spines, compound spikes fused to bases, and a sacral shield over the hips ornamented with a grid of small spikes. The ilium bones show fused pubes and ischia, with robust ridges and flanges that support the heavy armor.
Further back, two fused tail vertebrae resemble “handle” structures seen in later ankylosaurs, complete with ossified tendons. “The presence of ‘handle’ vertebrae in the tail of Spicomellus indicates that it possessed a tail weapon, overturning current understanding of tail club evolution in ankylosaurs, as these structures were previously thought to have evolved only in the Early Cretaceous,” the researchers note in the study.
This early tail adaptation suggests ankylosaurs developed weapons for defense or display far sooner than thought, possibly ancestral to the group. Phylogenetic analysis places Spicomellus as an early-diverging ankylosaurid, not part of a proposed southern clade, and implies that elaborate armor may have originated for show before simplifying for protection in later species.
The ornate spikes and plates would have been costly to grow and carry, hinting at roles in attracting mates or intimidating rivals. “The unique and ostentatious cervical armour of Spicomellus must have been energetically expensive to produce and carry,” the researchers note in the study. As predation increased in the Cretaceous with larger theropods and other threats, such armor might have shifted toward pure defense.
Citations
S. C. R. Maidment et al. Extreme Armour in the World’S Oldest Ankylosaur. Nature. Published online August 27, 2025. DOI: 10.1038/s41586-025-09453-6
