Chenanisaurus: a rare abelisaurid from latest Cretaceous Africa

Chenanisaurus barbaricus was a large predatory dinosaur from the latest Cretaceous phosphate deposits of Morocco. Its direct record consists of part of a lower jaw and a few isolated teeth. The fossils place an abelisaurid on mainland Africa late in the Maastrichtian, shortly before the Cretaceous–Palaeogene extinction. The dinosaur catalogue lists the genus among named dinosaurs, while the surviving bones set strict limits on what its profile can claim.

Quick facts

A jaw from a phosphate mine

The holotype, OCP DEK-GE 772, came from the Sidi Chennane mine in Morocco’s Ouled Abdoun Basin. It is a fragment of the left tooth-bearing bone of the lower jaw, with the bases of four tooth positions and three crowns preserved. Two isolated teeth, OCP DEK-GE 457 and OCP DEK-GE 458, were referred to the same species because their form and origin match the latest Maastrichtian material.

Nicholas Longrich, Xabier Pereda-Suberbiola, Nour-Eddine Jalil, Fatima Khaldoune and Essaid Jourani named the genus and species in 2017. The genus name refers to Sidi Chennane; barbaricus recalls the historical name Barbary and the Berber peoples of North Africa.

The setting is unusual for a dinosaur fossil. Moroccan phosphates are better known for marine vertebrates, including mosasaurs, sharks, bony fish and turtles. Land-animal remains entered this coastal marine basin only occasionally, perhaps carried by rivers or by floating carcasses. A jaw recovered from marine sediment does not mean the animal lived in the sea.

A short, deep lower jaw

The dentary is tall, robust and bends outward when viewed from above. The front of the lower jaw was especially short and strong. These proportions occur among abelisaurids, but are particularly pronounced in Chenanisaurus. The outer surface bears vascular openings and grooves. Its tooth row is comparatively straight along the upper edge, while the lower margin curves.

The teeth are flattened from side to side, curve backwards and carry serrated cutting edges. Together with the jaw shape, they identify a carnivorous animal able to slice flesh. They do not identify a particular prey species or show how the bite was delivered.

The preserved fragment can diagnose the species but cannot restore the whole skull. The nasal bones, eye region and roof of the skull are missing. A comparison with Carnotaurus helps illustrate the short, deep skull common among some abelisaurids, but does not show that Chenanisaurus had the same paired brow horns. Those parts of its head remain unknown.

How large was it?

The describing authors called Chenanisaurus one of the largest known abelisaurids. They estimated its size by comparing the depth of its dentary with the skulls of more complete relatives. Popular accounts often give a length of roughly 7–8 metres, but that figure is not a direct measurement: no vertebrae, pelvis or limb bones have been found.

Even scaling from the jaw carries wide uncertainty. Abelisaurids differed in the proportions of their heads and bodies, and the known animal may not have been fully grown or may have been unusually large. The defensible conclusion is that the jaw belonged to a large predator. Its exact length, height and mass are estimates.

The forelimbs are also unknown. Very short arms are usually shown because that arrangement is widespread among abelisaurids. It is a plausible reconstruction, but the number and shape of fingers in this genus have not been established from bones. The same caution applies to scaly skin: impressions exist for some relatives, not for this Moroccan animal.

An African abelisaurid lineage

Chenanisaurus belongs to Abelisauridae, a theropod family that was widespread across southern landmasses during the Cretaceous. The family includes Abelisaurus, which gave the group its name, and forms from South America, India, Madagascar, Europe and Africa.

Its deep, curved jaw resembles those of South American carnotaurines. However, the phylogenetic analysis in the original description did not confidently place Chenanisaurus within that branch. The result allows for an African abelisaurid lineage distinct from the better-known Late Cretaceous groups of South America, Indo-Madagascar and Europe.

This conclusion is provisional because so much of the skeleton is missing. Most characters from the complete skull and almost all postcranial characters are unavailable for analysis. A new fossil could substantially change the genus’s position. It is safest to call Chenanisaurus an abelisaurid without assigning it a close relationship to a particular South American species.

Noasaurids, including the smaller Masiakasaurus, were another branch of abelisauroids. Their unusual forward-pointing teeth differ markedly from the robust cutting teeth of Chenanisaurus; they are not a reliable model for its size or jaw mechanics.

One of Africa’s latest Cretaceous dinosaurs

The fossil-bearing horizon is latest Maastrichtian, the final stage of the Cretaceous. Chenanisaurus, alongside titanosaur remains, shows that a familiar Gondwanan community of large abelisaurid predators and plant-eating sauropods persisted in Africa late in the period.

This does not mean the jaw lay directly at the extinction boundary or that its owner died on the day the asteroid struck. In geological terms, “shortly before” may cover a substantial interval, and the age of marine phosphate beds depends on the resolution of local stratigraphy.

Hunting behaviour cannot be read from one bone. The strong jaw and cutting teeth indicate meat-eating, but reveal neither prey size nor whether the animal hunted alone or in groups. Titanosaurs and other terrestrial vertebrates lived in latest Cretaceous Africa, yet no described bite marks on their bones have been directly attributed to Chenanisaurus.

The full animal shown in a reconstruction follows the general body plan of a large abelisaurid. Colour, skin texture, skull details beyond the lower jaw and the surrounding scene are artistic choices. In the catalogue, Chenanisaurus is most valuable as a rare record of North Africa’s dinosaur fauna near the end of the Cretaceous.