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We describe two new pliosaurid specimens from upper Aptian beds near Villa de Leyva, Boyacá, Colombia. Morphological analysis reveals they represent a new brachaucheniine genus and species, Boyacasaurus sumercei gen. et sp. nov. Autapomorphies include: (1) an extremely elongated parasphenoid anterior projection surpassing the posterior interpterygoid vacuity margin, preventing midline pterygoid contact anterior to the posterior interpterygoid vacuity; and (2) palatines exhibiting a slope change near the midline, transitioning from a flat medial surface to a slightly dorsally inclined surface meeting the maxillae. Boyacasaurus is further distinguished by: maxilla forming anterior, lateral, and posterior halves of the internal naris margin; a short maxillary medial process posterior to the internal naris; a rounded basioccipital condyle lacking precondylar constriction and with a weakly developed ventral process; and palatines extending anteriorly beyond the pterygoid. Phylogenetic analysis places Boyacasaurus within Brachaucheniinae, closely related to long-snouted, subtrihedral-toothed pliosaurs Stenorhynchosaurus munozi and Luskhan itilensis. As the youngest recorded subtrihedral-toothed pliosaurid, Boyacasaurus demonstrates that the proposed decrease in Cretaceous pliosaurid dental disparity did not occur before the late Aptian.ZooBank LSID: urn:lsid:zoobank.org:pub:9F237C35-4DF9-467F-A2DB-A3FBD19CDA14
Benavides-Cabra et al. (Mon,) studied this question.