Taxonomic utility of Early Cretaceous Australian plesiosaurian vertebrae

Despite their broad occurrence in Australian basins, lower-level taxonomy of Early Cretaceous plesiosaurs is hindered by the scarcity skulls and other diagnostic elements. This paper presents a morphological morphometric analysis vertebrae comparison with selected non-Australian elasmosaurids (basal elasmosaurs, styxosaurines, aristonectines). Biometric involved measurements that include centrum height (CH), width (CW), length (CL), zygapophyses, others. Principal component (PCA) multivariate variance (MANOVA) were carried out on CH, CW, CL. Morphometric ratios [Vertebral Length Index (VLI), Height (HI), Breadth (BI)] plotted along vertebral column bivariate graphs where independent position correct sequencing. Direct homologous groups (especially anterior cervicals) easily distinguished an polycotylid from all plots. Most elasmosaurid specimens near basal ‘Cimoliasaurus’- grade they clustered as group relatively distinct from, but overlapping coeval forms. However, one specimen consistently styxosaurines Opallionectes andamookaensis aristonectines. Although it not possible to distinguish phylogenetic relationships convergence positions, analyses provide potential hypotheses be tested additional data. Hence, have some taxonomic value for assignment plesiosaurs, even absence or material.