Muiscasaurus

Muiscasaurus is an extinct genus of ophthalmosaurid Ichthyosaur that lived in modern Colombia during the Lower Cretaceous. The only known species is the type Muiscasaurus catheti.

The fossils of Muiscasaurus were found in the Paja Formation, whose sediments are exposed near the town of Villa de Leyva in Boyacá Department. These remains were found in 2010 in the middle of a limestone concretion, known as the Arcillolitas abigarradas Member, dating from the Barremian to Aptian epochs of the Lower Cretaceous. Although ammonites were found attached to the fossils, their poor preservation prevented identify them and thereby establish the stratigraphy and precise age of the specimen. The fossil found, listed as the holotype specimen CIP-FCG-CBP-74, consists of a partial skull and some vertebrae with ribs that were found associated with the skull. These remains were designated in 2015 as the new genus and species Muiscasaurus catheti; the genus name being a reference to the Muisca people of central Colombia, with the Latinized Greek word saurus, "reptile". The species name, catheti, means perpendicular and refers to the shape of the nostrils. The remains were prepared for the Centro de Investigaciones Paleontológicas (Paleontological Research Center) in Villa de Leyva.

The Muiscasaurus fossils corresponds to a juvenile individual, given the incomplete ossification of the vertebrae and the proportions of the skull. This lacks the front of the snout, as well as in the back of the skull, showing some crushing to the right side. The jaw elements are very thin and long, with some teeth preserved, which are relatively small. Muiscasaurus was a relatively large animal: the preserved skull length is 45 centimeters, and, depending on its exact proportions, could be between 48–65 cm total cranial length. This individual could reach 3 meters long and up to 5 meters long in adults. Like all advanced ichthyosaurs, Muiscasaurus must had a compact and streamlined body, with a tail shaped like a half moon and all four legs transformed into flippers.