Spicomellus afer

Spicomellus afer was an early-diverging ankylosaurian dinosaur with uniquely elaborate dermal armour, living in what is now Morocco during the Middle Jurassic period, approximately 168–166 million years ago (Bathonian stage). It was discovered in the El Mers III Formation of the Middle Atlas Mountains, a sedimentary deposit known for its continental and shallow marine facies.

The name Spicomellus combines the Latin “spica,” meaning “spike,” and “mellum,” referring to a collar, reflecting its distinctive spiked cervical half-ring. The species name “afer” is Latin for “African,” indicating its origin on the African continent.

As a member of the Ankylosauria within Thyreophora, Spicomellus represents the oldest definitive ankylosaur, offering insights into the early evolution of armoured dinosaurs in Gondwana.

Etymology

The genus name “Spicomellus” is derived from the Latin “spica,” meaning “spike,” and “mellum,” a term for a collar, alluding to the elaborate spiked cervical half-ring. The species name “afer” is Latin, meaning “from Africa,” reflecting its discovery in Morocco.

Physical Characteristics

Spicomellus afer was a medium-sized ankylosaur, estimated to reach 4 m (13 ft) in length. While modest compared to later ankylosaurids, its size is significant for an early-diverging form, with estimates based on the partial skeleton’s proportions relative to other basal ankylosaurs.

Key anatomical features include:

• A left quadrate with a broad, flattened articular surface and a robust shaft.
• Two cervical vertebrae, two dorsal vertebrae, four sacral vertebrae, and four free caudal vertebrae, with robust centra and well-developed neural arches.
• Two “handle” caudal vertebrae with ossified tendons, indicating a tail weapon, the oldest known in ankylosaurs.
• Six dorsal ribs with spikes fused directly to their dorsal surfaces, a unique trait among vertebrates.
• Both scapulocoracoids, ilia, pubes, and the right ischium, showing a broad, robust pelvic girdle.
• Two metatarsals with stout, cylindrical shafts.
• An elaborate cervical half-ring bearing two fused plates and five radiating spikes, the largest measuring 87 cm (34 in) long.
• A sacral shield with a mix of small and large spikes.
• Numerous plates, spikes of various morphologies, and compound osteoderms combining small and large spikes.

These features highlight an extreme dermal armour adaptation, with fused osteoderms suggesting both defensive and display functions.

Diet and Feeding Habits

As a herbivorous ankylosaur, Spicomellus afer fed on a variety of plants that thrived in the Middle Jurassic ecosystems of Gondwana. Its diet likely included:

• Ferns and cycads, abundant in its shallow marine and continental environment.
• Conifers, the dominant trees of the time.
• Early seed ferns, which were widespread during the Jurassic.

Like other ankylosaurs, Spicomellus probably used its broad beak and low-slung posture to crop vegetation at ground level, processing it with a battery of teeth adapted for grinding.

Habitat and Distribution

Spicomellus afer lived in what is now the Middle Atlas Mountains of Morocco, specifically in the El Mers III Formation of the El Mers Group, a geologic unit preserving continental mixed clastic, evaporitic, and carbonate sediments.

Its environment was characterized by:

• Shallow marine deposits with episodic incursions, indicating fluctuating sea levels.
• Continental floodplain and lagoon systems, supporting a humid, fertile landscape.
• Diverse vertebrate fauna, including stegosaurs, sauropods, and theropods.

The El Mers III Formation stands out as a rare Gondwanan site yielding ankylosaur remains.

Paleoenvironment

The discovery site was a shallow marine to continental transitional environment during the Middle Jurassic, with warm, humid conditions and periodic marine incursions. The fossil assemblage includes stegosaurs (Adratiklit, Thyreosaurus), a turiasaur, a neornithischian, theropod footprints, and crocodylomorph tracks, reflecting a rich, complex ecosystem.

Behavior and Social Structure

Although no direct evidence of social behavior exists for Spicomellus afer, ankylosaurs are often inferred to have lived in small groups or herds for protection. Possible behaviors include:

• Herding for defense, using its elaborate armour and tail weapon against predators.
• Display functions for the long cervical spikes, potentially in courtship or species recognition.
• Territorial defense with the tail weapon, a novel feature for early ankylosaurs.

Its quadrupedal stance and robust build suggest a lifestyle suited to browsing and deterring threats in a diverse predator-rich habitat.

Discovery and Research

The fossils of Spicomellus afer were first discovered in 2019 from the El Mers III Formation near Boulemane, Morocco. The holotype (NHMUK PV R 37412) is a rib fragment with fused osteoderms, while a 2023 expedition yielded a partial skeleton (USMBA 5–84), including cranial, vertebral, and dermal elements, confirming its ankylosaurian identity.

This discovery illuminates the early evolution of ankylosaurs, particularly in Gondwana.

Discovery Context

The initial specimen was acquired by the Natural History Museum, London, from a commercial dealer, with the locality traced to the El Mers III Formation. The 2023 expedition by an international team revisited the site, uncovering additional material despite illegal excavations. The site, dating to approximately 168–166 million years ago, is part of ongoing efforts to establish a protected area and train local paleontologists.

Significance and Interesting Facts

• The oldest definitive ankylosaur, predating Northern Hemisphere records by millions of years.
• First ankylosaur from Africa, expanding Gondwanan diversity within Parankylosauria.
• Features the earliest known tail weapon in ankylosaurs, challenging evolutionary timelines.
• Unique fused osteoderms and 87 cm (34 in) cervical spikes, unparalleled among vertebrates.
• Highlights a Southern Hemisphere radiation of thyreophorans alongside stegosaurs.

Conclusion

Spicomellus afer was a medium-sized, early-diverging ankylosaur from the Middle Jurassic of Morocco, showcasing the earliest and most elaborate dermal armour in its clade. Its tail weapon and ornate spikes suggest a dual role in defense and display, reflecting a complex evolutionary history in Gondwana. This 2025 discovery enriches our understanding of ankylosaur origins and diversification.