The newly-discovered dinosaur species, Spicomellus afer, is the earliest-known ankylosaur and the first ankylosaur to be named from Africa.
Life reconstruction of the armored dinosaur Borealopelta markmitchelli, which lived in what is now Alberta, Canada, some 110 million years ago, eating ferns. Image credit: Julius Csotonyi / Royal Tyrrell Museum.
Spicomellus afer lived in what is now Morocco during the Middle Jurassic period, some 168 million years ago.
The new species belongs to Ankylosauria, a diverse group of armored herbivorous dinosaurs.
Ankylosaurs diverged from their sister-taxon, Stegosauria, in the Early or Middle Jurassic, but their fossil record at this time is extremely sparse.
Spicomellus afer is not only the first found in Africa, but also the earliest example of the group ever discovered.
“Ankylosaurs had armored spikes that are usually embedded in their skin and not fused to bone,” said Dr. Susannah Maidment, a researcher in the Department of Earth Sciences at the Natural History Museum and honorary senior lecturer in the School of Geography, Earth and Environmental Sciences at the University of Birmingham.
“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.”
The specimen of Spicomellus afer consists of a rib with spiked dermal armor fused to its dorsal surface. Image credit: Maidment et al., doi: 10.1038/s41559-021-01553-6
The new specimen is a slightly curved dorsal rib fragment with four elongate, conical spines.
It was found at a site in the Middle Atlas Mountains in Morocco — the same site where paleontologists previously discovered Adratiklit boulahfa, the oldest stegosaur ever found.
“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.”
The specimen fills a gap in the fossil record of Ankylosauria, suggesting that shortly after their evolution, ankylosaurs had attained a global distribution, and indicates an important but as yet undiscovered armored dinosaur fossil record in the Jurassic of the supercontinent Gondwana.
The discovery also calls into question a previous theory that ankylosaurs outcompeted stegosaurs and led to their extinction.
“Stegosaurs appear to have gone extinct in the Early Cretaceous, at the same time that ankylosaurs increased in diversity, leading to suggestions that ankylosaurs outcompeted stegosaurs,” the paleontologists said.
“However, both clades co-occurred in Jurassic ecosystems. This indicates long-term ecological overlap between stegosaurs and ankylosaurs for over 20 million years, suggesting that the decline of stegosaurs may have been for reasons other than competition with ankylosaurs.”
The study was published in the journal Nature Ecology & Evolution.
S.C.R. Maidment et al. Bizarre dermal armour suggests the first African ankylosaur. Nat Ecol Evol, published online September 23, 2021; doi: 10.1038/s41559-021-01553-6