Spicomellus: an early ankylosaur with extraordinary armour

Spicomellus afer was a four-legged plant-eating ankylosaur from the Middle Jurassic of what is now Morocco. It lived during the Bathonian, approximately 168.2–165.3 million years ago, making it the oldest securely identified ankylosaur currently known. Its fossils are remarkable for armour unlike that of later members of the group: long spikes were fused directly to ribs, and a massive neck half-ring carried five projections, two approaching a metre in length.

The first published account was based on a single incomplete rib and left important questions about the animal’s identity and anatomy. A more complete collection found at the same locality in 2023 and described in 2025 confirmed its place among ankylosaurs. The fossils show an early experiment in armour, but they do not reveal exactly how the spikes were used. Spicomellus belongs in the dinosaur catalogue, where it can be compared with the later armoured dinosaurs Pinacosaurus and Polacanthus.

Quick facts

Name and discovery

The name Spicomellus combines Latin elements associated with a spine and a spiny collar; it is commonly rendered as “spiked collar”. The species name afer means African. The name became especially apt after the discovery of the neck armour, although the first fossil known to science was a rib with attached spikes rather than the collar itself.

The Natural History Museum in London acquired the rib fragment NHMUK PV R 37412 from a fossil dealer in 2019. Four bony spikes attached to a flat base on the rib made the specimen unlike familiar ankylosaur armour. In 2021, Susannah Maidment and colleagues described Spicomellus afer from this material. With only one incomplete rib, however, the animal’s broader anatomy and even the interpretation of its unusual armour could not be tested against a skeleton.

An expedition to the type locality on the Bou Iahfa plain recovered additional fossils in 2023. They were catalogued as USMBA 5–84 and are held by the University of Sidi Mohamed Ben Abdellah in Fez. Their description in 2025 supplied more of the postcranial skeleton, including the extraordinary neck half-ring, and confirmed the ankylosaur nature of the genus. The two discoveries answer different questions: the first established the strange rib armour, while the later material provided a stronger anatomical context.

Classification and evolutionary setting

Spicomellus is an ornithischian within Thyreophora, the group of armoured dinosaurs, and is classified as an ankylosaur. The more complete material supports this placement through the structure of the skeleton, rather than relying only on the microscopic character of one osteoderm. Its Middle Jurassic age places it early in the history of ankylosaurs.

It is not simply a primitive version of a familiar Late Cretaceous ankylosaur. Its armour shows a combination of features that is not seen in later members. The direct fusion of spikes to ribs is especially unusual. These differences document anatomical diversity, but a single early genus cannot establish a simple ladder of evolution from one armour design to another.

The evolutionary relationships among early thyreophorans remain an area where new fossils can have a large effect. The incompleteness of many Jurassic skeletons makes comparisons difficult. Spicomellus now contributes several important parts, but researchers still need to evaluate its characters alongside other early armoured dinosaurs before drawing detailed conclusions about its closest relatives.

Fossils and geological age

The fossils came from the El Mers III Formation in Morocco, on the Bou Iahfa plain. The rocks are assigned to the Bathonian stage of the Middle Jurassic, about 168.2–165.3 million years old. The age is an estimate based on geological correlation, not a direct measurement of the animal’s lifespan.

The holotype material includes the rib fragment NHMUK PV R 37412. The additional collection USMBA 5–84 contains associated postcranial remains from the type locality. The specimens are not a fully articulated, complete skeleton. The collection therefore expands the anatomical record considerably without filling every gap, particularly for the skull and many details of the limbs and tail.

Association and locality information matter when fossils are combined. Material from the same site can belong to one taxon without belonging to one individual. The 2025 description treated the new material as Spicomellus based on its occurrence and anatomical fit with the first specimen. Future discoveries can further test how the different bones relate to one another.

Body and unusual armour

Spicomellus was a quadrupedal herbivore. A body length of roughly four metres has been estimated, but the fossil record does not preserve a complete skeleton from nose to tail, so the figure is approximate. Any estimate of mass would be even more model-dependent. The animal’s broad body plan can be compared with other ankylosaurs, but its full outline is not directly preserved.

The best-known feature is a complex arrangement of spikes. Bony projections were fused to the dorsal ribs, rather than merely lying loose in the skin. The neck half-ring was a substantial structure bearing five spikes. Two of them approached a metre long, an exceptional size relative to the preserved material. These bony parts demonstrate an imposing defensive covering around the front of the body.

Osteoderms are bones formed within the skin. Their attachment, shape and orientation can show how armour was constructed, but they do not preserve the complete external surface. Keratinous coverings, skin folds and colour are not known. A reconstruction must supply these soft tissues and fill the gaps in the skeleton; the spikes themselves are fossil evidence, while the precise living silhouette is a hypothesis.

Habitat, diet and possible function

During the Bathonian, the area that is now Morocco supported environments very different from the modern landscape. Spicomellus lived on a continental setting recorded by the El Mers III rocks. The fossils establish where its remains were buried; they do not map every habitat used by the living animal.

Its beaked ornithischian ancestry and ankylosaur body plan support a plant-eating interpretation. No known gut contents identify particular food plants, and the incomplete skull does not permit a detailed reconstruction of its bite. Claims about exact diet, feeding height or daily routine would go beyond the available evidence.

The spikes were likely part of a defensive system, but their exact function is unknown. They may have made the animal more difficult to attack or affected how it presented its body to a threat. A role in display or species recognition is possible, yet the fossils preserve structure, not observed behaviour. The long projections should not be described as proof of how Spicomellus fought.

What remains uncertain

The animal’s unusual armour once invited doubt about whether it belonged among ankylosaurs. The 2025 material strengthened that identification by providing a broader skeletal context. That progress does not mean every anatomical question has been answered: the skeleton remains incomplete, its closest relatives need further comparison, and much of its life appearance is reconstructed.

No direct evidence identifies its sex, social behaviour, colour, nesting habits or lifespan. A distinctive armour pattern can inspire ideas about defence and display, but cannot decide between them alone. Spicomellus is most informative when its preserved spikes and bones are separated from the plausible, but unproven, stories built around them.

Its importance lies in extending the record of ankylosaurs deep into the Jurassic and revealing a striking early armour design. The change from an isolated rib to a broader fossil collection also shows how new fieldwork can transform a taxon’s interpretation. More complete specimens may eventually clarify the body, relationships and function of its armour.