Chenanisaurus is a species of predatory abelisaurid theropod dinosaur from the upper Maastrichtian phosphates of the Ouled Abdoun Basin in Morocco, North Africa. It is known from a holotype consisting of a partial dentary and four teeth and a few isolated teeth attributed to it.[1]
Description[]
Chenanisaurus is quite a large abelisaurid, measuring Template:Convert, based on measurements of the holotype dentary, surpassed or rivalled in size only by such known abelisaurids as Carnotaurus and Pycnonemosaurus.[1]
Nicholas R. Longrich and colleagues, the describers of Chenanisaurus, were able to establish some distinctive features. The lower jaw is high, while the dentary is bent in side view. The lateral groove and associated foramina are located high on the outer surface of the dentary. The anterodorsal margin of the dentary is curved downward. The symphysis of the lower jaws is heavily built while the leading edge is vertical in side view. The front jaw points are wide in plan view, encountering each other at an obtuse angle.
The most striking feature of the mandible is the extreme height, especially when compared with the relatively short teeth. This seems to indicate that the jaw is also very short, with a build even more extreme than seen in the related genus Carnotaurus. The jaw flexes forwardly downwards to terminate in a deep blunt point. At the back there is a deep high furrow above it with a row of foramina that open towards the top in a series of vertical grooves. The high position is a basal characteristic. The outer lower side shows an ornamentation of pits and interweaved ridges. The front interdental plates are very high but they quickly lower towards the rear of the jaw. The tooth sockets are rectangular in upper view. The jaw carries at least ten teeth. These are relatively slender, but the front teeth have a D-shaped cross section with the convexity facing outward; the rear teeth are dagger-shaped and more flattened. The cutting edges are convex and show up to thirteen denticles per five millimetres at the crown base, and up to eight denticles near the apex. They have small blood grooves. The enamel has an irregular structure without clear ornamentation.[1]
Discovery and naming[]
The holotype is labelled as OCP DEK-GE 772. Individual teeth collected from the surrounding area, two premaxillary teeth labelled as OCP DEK-GE 457 and DEK-GE 458 and the maxillary tooth WDC-CCPM-005 already described in 2005,[2] were referred to Chenanisaurus due to their similarity to the teeth of the holotype. Chenanisaurus is named after the Sidi Chennane mines where it was discovered and its specific name of barbaricus translates as "barbaric" and refers to Barbary.[1]
Classification[]
In 2017, Chenanisaurus was placed in Abelisauridae in a basal position outside the Abelisaurinae and Carnotaurinae. Though it resembles carnotaurine abelisaurids in aspects of its jaw morphology, Chenanisaurus may belong to an as-yet undescribed group of abelisaurids unique to Africa. Only further research will determine the true relations of this species.[1]
Paleobiology[]
Chenanisaurus was a predator, like other abelisaurids. Given its size, it could have hunted relatively large prey. The short head and jaws which this abelisaurid had in conjunction with high, solidly built front teeth, is explained as an adaptation as a special hunting tactic of the animal, with gaping jaws ramming the sides or flanks of its prey in order to tear off a chunk of meat. In the same layers in which Chenanisaurus is found, remnants of titanosaurs have also been found, which would have been suitable prey. The describers indicated that other continents previosuly part of Gondwana also show a comparable combination of titanosaurid and abelisaurid fauna. The finding of Chenanisaurus and these fragments of titanosaurids also indicate that in Africa, an abelisaurid/titanosaur fauna existed just prior to the Cretaceous–Paleogene extinction event, suggesting that the faunal assemblage of Gondwana was relatively stable until that point in time.[1] Interestingly, Chenanisaurus' remains were found in marine deposits that comprise most of the Sidi Chennane phosphate mines, indicating that post-mortem, the theropod had washed out to sea, where the holotype specimen became fossilized.[3]