In what can be perhaps best described as a “living tank,” ankylosaurs (ann-KIL-luh-saurs) are among the most bizarre dinosaurs out there. With a lineage spanning from around the early Jurassic period some 201 million years ago up till the end of the Age of Dinosaurs some 65 million years ago, these animals roamed the Earth at what now comprises the Northern Hemisphere.
These animals’ names are derived from the Greek for “fused lizard,” as evidenced by what is perhaps their most common trait: their backs are littered with keratin plates that possibly served as protection for the animal against predators, much like how turtles use their own shell today. These herbivorous, or plant-eating, dinosaurs are a sister group to the stegosaurs, a similar group of dinosaurs with plates on their back, yet are mostly upright unlike their “tanky” cousins. Alongside these bony back plates, ankylosaurs are also known for possessing “clubbed” tails with growths at the tip; these tails were also believed to have been used in self-defense, similar in function to a “blunt” flail.
Ankylosaurs are considered some of the most successful ornithischian (“bird-hipped”) dinosaurs, outliving even their stegosaurid cousins up until the meteorite impact 65 million years ago that wiped non-avian dinosaurs off the face of the planet. However, much like the rest of the dinosaur family now frozen in time as fossils, our knowledge of them is spotty at best, Luckily for science, a recent find adds one more piece to the ankylosaur puzzle: the discovery of what appears to be a 168-million-year-old ankylosaur in what is now Morocco. The find was revealed in a study that was published in the journal Nature Ecology & Evolution.
The find, a fossil of a piece of a dorsal rib, was found in a dig site located atop the Middle Atlas Mountains of Morocco. The fossil also features four conical “spikes,” arranged along the length of the rib fragment. (Interestingly, the same dig site also yielded Adratiklit boulahfa, the oldest stegosaur fossil ever found, some two years prior.)
The research team identified the find as an ankylosaur right away, given CT scans of the find that revealed a “cross-hatch” pattern in the bone that they say is unique to ankylosaurs. With the bone fossil having been dated to around 168 million years old, Spicomellus afer is now recognized as not just the first-ever ankylosaur fossil found in Africa; it may also be the oldest ankylosaur ever found, according to the team of researchers who worked on the find.
However, the team found something odd about S. afer’s remains: it appears that the spikes it had were attached to the rib.
You see, ankylosaur keratin plates are often found detached from the rest of the bones of a specimen’s body; to the scientists, this means that ankylosaurs grew these bony plates “outside” their bodies, right above where the skin would be in the living animal. This would be similar to how your body arranges itself with respect to fingernails: first the bone inside, then muscle, the skin above that, and finally the keratin fingernail (yes—ankylosaurs plates and fingernails are made of the same protein) at the very top.
However, in the case of S. afer, the spikes grew right above the bone itself, meaning skin simply grew around these spikes back when the animal was alive. First impressions led the scientists to believe that this could have hindered muscular movement in some way.
Dr. Susie Maidment, National History Museum researcher and professor at the University of Birmingham, believes the animal to be “completely unprecedented and unlike anything else in the animal kingdom.”
Dr. Maidment followed: “Morocco seems to hold some real gems in terms of dinosaur discoveries;” and after recalling the previous stegosaur find in A. boulahfa: “In just this one site we have described both the oldest stegosaur and the oldest ankylosaur ever found.”
The coexistence of both stegosaurs and ankylosaurs in one area led Maidment and the team to question the notion that ankylosaurs outcompeted their fellow plated cousins for resources, leading to an earlier extinction for the stegosaurs. (Stegosaurs went extinct at the end of the Jurassic period some 145 million years ago; ankylosaurs outlived them by about 80 million years.)
“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,” according to the team. “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.”
In the future, Dr. Maidment and team hopes to continue their work on dinosaur research in the area. “When circumstances allow, we hope to return and work with our colleagues at the University of Fez to help them to establish a vertebrate paleontology lab so that further finds can be studied in Morocco.”
(To read more about unique dinosaur finds, check out Australia’s largest titanosaur find so far, and Uzbekistan’s carcharodontosaur find which may have been the last of its kind.)
References
- Amos, J. (2021, September 23). Dinosaurs: “Bizarre” fossil is Africa’s first ankylosaur. BBC News. https://www.bbc.com/news/science-environment-58657862
- de Lazaro, E. (2021, September 24). Fossil of Earliest Known Ankylosaur Unearthed in Morocco. Sci-News. http://www.sci-news.com/paleontology/spicomellus-afer-10102.html
- Maidment, S. C. R., Strachan, S. J., Ouarhache, D., Scheyer, T. M., Brown, E. E., Fernandez, V., Johanson, Z., Raven, T. J., & Barrett, P. M. (2021). Bizarre dermal armour suggests the first African ankylosaur. Nature Ecology & Evolution, 1–6. https://doi.org/10.1038/s41559-021-01553-6
- Sci-News. (2019, August 22). Meet Adratiklit boulahfa, World’s Earliest Known Stegosaur. Sci-News. http://www.sci-news.com/paleontology/adratiklit-boulahfa-07518.html
- University of Birmingham. (2021, September 24). Bizarre armoured spikes belong to oldest ankylosaur ever discovered. https://phys.org/news/2021-09-bizarre-armoured-spikes-oldest-ankylosaur.html
