Giant pliosaurids (Sauropterygia; Plesiosauria) from the Lower Cretaceous peri-Gondwanan seas of Colombia and Australia

Kronosaurus boyacensis is the most famous and most important Lower Cretaceous marine reptile fossil recovered from the Villa de Leyva region of Boyacá, Colombia, northern South America. To the local population it has become iconic as The Fossil (‘El Fósil’) of Colombia. Here we provide a detailed re-description of the holotype of the pliosaurid sauropterygian Kronosaurus boyacensis, and designate it a new genus, Monquirasaurus. Redescription of Monquirasaurus boyacensis required detailed consideration of the genus Kronosaurus, the Albian holotype of which is non-diagnostic at the taxonomic level of genus and species so the name Kronosaurus queenslandicus is thereby restricted to the holotype only. Aptian specimens currently assigned to Kronosaurus queenslandicus, and housed in the University Museum in Harvard, USA, are designated as the holotype and referred specimen of the new genus and species Eiectus longmani, which also provisionally includes all Albian material formerly referred to the genus Kronosaurus. The two pliosaurid marine reptiles from the Cretaceous of Colombia and Australia do not fit well into the current phylogenetic framework proposed for these gigantic marine reptiles, highlighting the importance of both northern and southern peri-Gondwanan specimens for the study of Lower Cretaceous Gap pliosaurids.