Neuroanatomy of the vertebral column of Vegasaurus molyi (Elasmosauridae) with comments on the cervico-dorsal limit in plesiosaurs

JOSÉ O´GORMAN; MARTA S. FERNÁNDEZ

CRETACEOUS RESEARCH (PRINT)

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017

0195-6671

The evolution of the axial skeleton of vertebrates, particularly regionalization and the changes in thelimits of each region is yet to be completely understood. The features of this process are more difficult tofollow in groups with strong changes in the number of vertebrae as is the case of plesiosaurs. In this workwe record the osseous correlates of the nervous system housed in the neural channel along the vertebralcolumn of the elasmosaurid Vegasaurus molyi, from the lower Maastrichtian levels of the Snow Hill IslandFormation (Antarctica). The new data allows inference of the position of the brachial plexus (i.e. theinnervation of the pectoral girdle and anterior limbs), which in turn allows identification of the positionof the pectoral girdle and the homology of the transitional ?pectoral? region and the anterior dorsal(¼trunk) vertebrae. The results indicate that in Vegasaurus molyi the pectoral girdle is at the level of theso called ?pectoral? region, and that the pectoral region is homologous to the anterior trunk vertebrae ofother Sauropsida. Additionally, the comparison with other published results of polycotylids showingdifferences with V. molyi suggesting an interesting difference in the pattern of vertebral columnregionalization among plesiosaurs