📸 The Kem Kem Beds (Source: Nizar paper)
In the thick of a brackish swamp that stretches for miles in every direction, a lumbering Spinosaurus battles the agile Carcharodontosaurus, two apex predators locked in an epic struggle. Whichever one wins will have plenty more competition to face: this swampland is home to many species of carnivorous theropods, each looking to make a name for itself. This is the scene in what is now Northern Africa, 66 to 100 million years ago, a violent climax at the end of the Age of Dinosaurs. What remains of these fearsome predators is now locked away in Morocco’s Kem Kem Formation, one of the best sources of Late Cretaceous fossils in the world.
📸 Kem Kem's stratigraphic layers exposed. (Source: Nizar paper)
The Kem Kem Group is a collection of strata composed of the smaller Gara Sbaa and Douira formations, exposed on a cliff face along the Morocco-Algerian border. Underneath a top layer of limestone deposited during the Cenomanian-Turonian extinction event is a bonafide treasure trove of theropod remains, along with armored fish, aquatic Crocodyliforms, and plant life. Still, it is the predators that dominate the strata in death as they did the land in life, with four large-bodied theropods identified: Spinosaurus, Carcharodontosaurus, Deltadromeus and an as yet unassigned abelisaurid.
Kem Kem has shed much light on this clade of dinosaurs, but the formation may be a victim of its own success. The question has been raised whether Kem Kem is an accurate snapshot of the Late Cretaceous, or if the formation is an example of time-averaging, when disparate fossils are brought together into the same strata. 70% of Kem Kem fossils are predators, an unusually high number, especially considering the small amount of sauropods and other prey species recovered. Local fossil hunters also tend to focus on the more valuable predator teeth, possibly misrepresenting the ratio between the two.
📸 A Carcharodontosaurus skull.
Regardless of whether Northern Africa was truly dominated by theropods, the Kem Kem Group has still taught us much about these fearsome predators. Armored fish were first described in 1948, with small finds of other vertebras following over the next couple years. Discoveries were sporadic over the next few decades until 1995, when Paul Sereno rediscovered Carcharodontosaurus, after its original holotype was destroyed during the Second World War. Sereno dubbed his find “Africa’s answer to Tyrannosaurus,” although the genus was actually more closely related to the bigger Giganotosaurus.
Faced with a dearth of prey on land, Carcharodontosaurus and its other theropod cousins would have had to take food wherever they could. The semi-aquatic Spinosaurus was perfectly suited to the region’s floodplains, patrolling the riverways for the abundant fish just below the surface. The predator had unusually dense bones, an adaptation that allowed it to more easily submerge under water. With large conical teeth perfect for catching aquatic prey, the Spinosaurus carved out a specialized niche for thriving in this region. Other less well-adapted genera could have gone as far as resorting to cannibalism if their food source dried up.
In the shadow of these massive theropods were other vertebrates, predators to compete with or prey to hunt. Along the waterways, Spinosaurus would have fed alongside Cartilaginous sharks, armored fish, and Crocodylomorphs, similar to modern crocodiles. If competition was too stiff, Spinosaurus might look to the air and snatch a low-flying pterosaur like Alanqua. Underneath these dramatic hunting scenes, snakes and small amphibians like Oumtkoutia frogs would have mostly escaped notice, thriving in the swampy terrain and amidst the towering conifer trees that have also been found preserved at Kem Kem.
📸 A Spinosaurus tooth.
Carcharodontosaurus, Spinosaurus and other theropods are best known at Kem Kem from their abundant teeth. In fact, sometimes caches of tooth fossils are discovered in the thousands. Why so many teeth when skeletal fossils from these creatures are extremely rare? There are a couple of factors to this.
First, a single Spinosaurus usually had over 40 teeth in its jaws at once and would lose and regrow hundreds throughout their lifetime. That is already a big tooth to skeletal ratio. A tooth’s tough enamel is also more easily preserved than normal bone. When you look at how long the Spinosaurus lived in this area, over 5 million years, that ends up being at least hundreds of millions of teeth. Even if only a small percentage were fossilized, that is still a lot of material waiting to be discovered in the fossil beds.
A side effect of these massive amounts of teeth is the further compounding of the predator controversy around Kem Kem. Did the region actually support a disproportionately high number of theropods, or does the amount of teeth from these predators skew our perception? It is a question without an obvious answer, but hopefully as more work continues at Kem Kem, a clearer picture will dawn of the region.
The Kem Kem Group is a reminder of the limitations paleontologists face when speculating on the past. The appearance of two fossils together does not always suggest a relationship, just as the absence of a fossil does not mean that an organism was not present. There is always speculation and hypotheticals in science. For now, Kem Kem is one possible world of the Late Cretaceous, a place where predators were not a small class but the dominant population, competing with each other for whatever prey was to be had.
Further Reading
Beevor, Thomas, et al. “Taphonomic Evidence Supports an Aquatic Lifestyle for Spinosaurus.” Cretaceous Research, vol. 117, 2021, p. 104627–, https://doi.org/10.1016/j.cretres.2020.104627.
Dyke, Gareth J. “Palaeoecology: Different Dinosaur Ecologies in Deep Time?” Current Biology, vol. 20, no. 22, 2010, pp. R983–R985, https://doi.org/10.1016/j.cub.2010.10.001.
Ibrahim, Nizar, et al. “Geology and Paleontology of the Upper Cretaceous Kem Kem Group of Eastern Morocco.” ZooKeys, vol. 928, 2020, pp. 1–216, https://doi.org/10.3897/zookeys.928.47517.