New mid-cervical vertebral morphotype of Spinosauridae from the Kem Kem Group of Morocco

Abstract

An unusual mid-cervical vertebra belonging to a large spinosaurid from the Cenomanian Kem Kem Group of Morocco is described. It is compared to the characteristic morphology of each reconstructed cervical position in Spinosaurus aegyptiacus, based on a recent composite reconstruction that incorporates most previously referred material from this unit. Rather than conforming to any of the previously identified cervical positions in its morphology, the specimen displays a unique combination of mid-cervical characters, with the relatively compact centrum suggesting a position as C4, and the form of the neural arch laminae suggesting a position as C5 or C6. Furthermore, it displays two characters that are previously unknown in spinosaurid mid-cervicals from the Kem Kem Group: a rounded hypapophyseal tuberosity that is not continuous with a ventral keel, and a moderately developed, dorsally oriented epipophysis that does not overhang the postzygapophysis posteriorly. The diagnostic value of positionally variable cervical vertebral characters in spinosaurid systematics is discussed. Although limited, the new data could lend support to the controversial hypothesis that two spinosaurid taxa are represented in the Kem Kem Group.

New spinosaurids from the Wessex Formation (Early Cretaceous, UK) and the European origins of Spinosauridae

“…Similarly, differing topologies recovered within Spinosaurinae indicate a continued lack of in-group resolution. This impacts the perceived number of coeval North African spinosaurines, a topic that has attracted considerable debate in recent years 7,22,27,84 . The polytomous, parsimony-based strict consensus, coupled with the insignificance of the constrained analysis performed to group North African specimens (see SI), are unable to support or reject the existence of a spinosaurine subclade incorporating all North African material-a topology required to corroborate the proposed synonymy of these specimens (i.e.…”