Approximately 168 million years ago, Spicomellus afer lived in the area that is now Morocco in the Middle Jurassic period. New species of the Ankylosauria family of herbivorous dinosaurs belong to this group. The Ankylosaurs diverged from their sister-taxon, Stegosauria, in the Early or Middle Jurassic, but their fossil record is sparse at this time. The Spicomellus afer is not only the first specimen discovered in Africa, but also the earliest example ever found.
‘Ankylosaurs had armored spikes that are usually embedded in their skin and not fused to bone,’ says Dr. Susannah Maidment, a researcher at the Natural History Museum and honorary senior lecturer at the University of Birmingham’s School of Geography, Earth and Environmental Sciences. ‘In this specimen we see a series of spikes attached to the rib, which must have protruded above the skin covered by a layer of something like keratin. It is completely unprecedented and unlike anything else in the animal kingdom.’ This specimen is a dorsal rib fragment with four elongate, conical spines.
The fossil was discovered in the Middle Atlas Mountains in Morocco, the same region where paleontologists previously discovered Adratiklit boulahfa, the oldest stegosaur ever discovered. ‘Morocco seems to hold some real gems in terms of dinosaur discoveries,’ Dr. Maidment said. ‘In just this one site we have described both the oldest stegosaur and the oldest ankylosaur ever found.’
Ankylosaurs may have attained an extended global distribution shortly after their evolution, thanks to this specimen, that suggests an important and until now undiscovered presence of armored dinosaurs in the Jurassic of the supercontinent Gondwana. The discovery also calls into question a previous theory that ankylosaurs outcompeted stegosaurs, resulting in their extinction. According to paleontologists, stegosaurs went extinct in the early Cretaceous at the same time that ankylosaurs increased in diversity, suggesting that ankylosaurs outcompeted stegosaurs. Both clades, however, coexisted in Jurassic ecosystems. It indicates 20 million years of ecological overlap between stegosaurs and ankylosaurs, which suggests the decline of stegosaurs was not caused by competitor pressures from ankylosaurs.
An article on the study was published in ‘Nature Ecology & Evolution’.