Virtual reexamination of a plesiosaurian specimen (Reptilia, Plesiosauria) from the Late Cretaceous (Turonian) of Goulmima, Morocco, using computed tomography

ABSTRACT

Turonian deposits of the Goulmima area, Er-Rachidia Province in southern Morocco, have yielded a diverse marine vertebrate fauna, including chondrichthyans, bony fishes, and large marine reptiles such as plesiosaurians, mosasauroids, and turtles. These fossils are included in ovoid calcareous nodules that are difficult to prepare. Moreover, bones may be partially or totally dissolved, making their study difficult. Using computed tomography, we have reconstructed the entire skull anatomy of SMNS 81783, one of the rare plesiosaurian specimens found in this locality and more generally in Africa. The digital three-dimensional reconstruction of the skull and the mandible offers for the first time the possibility to describe this specimen exhaustively. The new anatomical characters recorded confirm that SMNS 81783 belongs to Elasmosauridae on the basis of (1) slender and triangular skull; (2) beak index equal to 42%; (3) temporal fossa estimated to occupy about 40% of the skull length; (4) long process of the premaxillae extending posteriorly to meet the parietal above the orbit and separating the frontals; and (5) margin of the temporal fenestra lacking obvious contribution from the frontal. A preliminary phylogenetic analysis confirms its elasmosaurid affinity. The relationships between SMNS 81783, Libonectes atlasense, and Libonectes morgani, as well as the presence of stapes and pineal foramen, are discussed.

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Citation for this article: Allemand, R., N. Bardet, A. Houssaye, and P. Vincent. 2017. Virtual reexamination of a plesiosaurian specimen (Reptilia, Plesiosauria) from the Late Cretaceous (Turonian) of Goulmima, Morocco, using computed tomography. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1325894.

ACKNOWLEDGMENTS

This work was supported by a grant from the Agence Nationale de la Recherche under the LabEx ANR-10-LABX-0003-BCDiv, in the program ‘Investissements d'avenir’ ANR-11-IDEX-0004-02. We are grateful to the Staatliches Museum für Naturkunde Stuttgart for the loan of the specimen SMNS 81783 and to E. Maxwell for access to the collection of the Stuttgart museum. We thank the AST-RX platform at the MNHN for access to the CT scan, and M. Garcia Sanz (MNHN, UMS 2700 OMSI) for producing the CT scans, and F. Goussard (MNHN, UMR 7207 CR2P) for assistance with 3D digital reconstructions and imaging based on CT scans. We are very grateful to D. Germain (MNHN, UMR 7207 CR2P) for his help with the use of T.N.T. We thank S. Sachs (Naturkundemuseum Bielefeld, Abteilung Geowissenschaften, Germany) and B. Kear (Museum of Evolution, Uppsala University, Sweden) for general discussion. Finally, we thank P. Druckenmiller and both reviewers, Robin O'Keefe and Rodrigo Otero, for helpful comments and suggestions.