Spicomellus

Spicomellus is an extinct genus of unusual early ankylosaurian dinosaur from the El Mers III Formation (Bathonian age) of Morocco. The genus contains a single species, Spicomellus afer, representing the oldest named definitive ankylosaur. The species was initially described in 2021 based on a single rib with fused osteoderms, rendering its life appearance and relationships uncertain. In 2025, several additional bones, including osteoderms and cranial and postcranial remains, were described, revealing that it bears a unique array of spines over the body, including extremely elongated spikes around the neck and pelvis. It likely had a tail weapon, making it the oldest known ankylosaur with this structure.

==Discovery and naming== left|thumb|Illustration of the Spicomellus holotype In 2019, the Natural History Museum in London acquired an unusual Moroccan fossil from a commercial fossil dealer in Cambridge. The specimen consists of a single dorsal rib fragment fused to a flat osteoderm bearing four spines on the external surface. After discussions with the English seller and the Moroccan fossil dealer from whom the specimen was obtained, English paleontologist Susannah Maidment and Moroccan geologist Driss Ouarhache were able to relocate the locality from which the specimen was collected. It originates from layers of the El Mers III Formation in the Middle Atlas mountains near the town of Boulemane in Fès-Meknès region, Morocco. Maidment and Ouarhache visited this location in 2019 and 2020, respectively, to examine its sedimentology and stratigraphy. The specimen was scanned using X-ray computed tomography (XCT) and histologically sectioned to confirm its authenticity and ankylosaurian nature.