| Muiscasaurus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Ichthyosauria |
| Family: | †Ophthalmosauridae |
| Genus: | †Muiscasaurus Maxwellet al.,2015 |
| Type species | |
| †Muiscasaurus catheti Maxwellet al., 2015 | |
Muiscasaurus is an extinctgenus ofophthalmosauridichthyosaur that lived in modernColombia during theEarly Cretaceous. The only known species is thetypeMuiscasaurus catheti.[2]
The fossils ofMuiscasaurus were found in thePaja Formation, whose sediments are exposed near the town ofVilla de Leyva inBoyacá Department. These remains were found in 2010 in the middle of a limestone concretion, known as the Arcillolitas abigarradas Member, dating from theBarremian toAptian epochs of the Lower Cretaceous. Althoughammonites were found attached to the fossils, their poor preservation prevented identifying them and thereby establish thestratigraphy and precise age of the specimen. The fossil found, listed as theholotype 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 speciesMuiscasaurus catheti; the genus name being a reference to theMuisca of central Colombia, with the LatinizedGreek wordsaurus, "reptile". The species name,catheti, meansperpendicular 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.[2]
TheMuiscasaurus 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 centimetres (18 in), and, depending on its exact proportions, could be between 48–65 centimetres (19–26 in) total cranial length.[2] This individual could reach 3 metres (9 ft 10 in) long and up to 5 metres (16 ft 5 in) long in adults.[3] Like all advanced ichthyosaurs,Muiscasaurus must had a compact andstreamlined body, with a tail shaped like a half moon and all four legs transformed into flippers.[3]
Muiscasaurus differs from its closest relatives by a combination of features: it had a very thinpremaxilla, the nasal aperture is partially divided in two ovals for a spur-shaped nasalprocess, with the frontal portion in vertical position and the rear one horizontal; in other ophthalmosaurid ichthyosaurs, the aperture was fully open or fully separated into two. The posterior region was narrow and provided with a thinquadratojugal, the teeth were very thin and lacking of the thick enamel and the coarse striations, whereas in similar ichthyosaurs asPervushovisaurus andPlatypterygius had more robust teeth and grooves in theenamel.[2]
Muiscasaurus was described based on fossils that were classified as belonging to theOphthalmosauridae family, which includes most of the ichthyosaurs that lived during theJurassic andCretaceous periods.Muiscasaurus seems particularly occupied a verybasal position within the family, with respect to the subgroup composed byPlatypterygius,Caypullisaurus andBrachypterygius (although the latter two genera were slightly older thanMuiscasaurus itself) .[2]
Cladogram based in thephylogenetic analysis of Maxwellet al., 2015:
The following cladogram shows a possible phylogenetic position ofMuiscasaurus in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).[4]
| Ophthalmosauria |
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
In addition toMuiscasaurus, in the Paja Formation has been recovered other kind of ichthyosaur,Kyhytysuka sachicarum; it is distinguished ofMuiscasaurus for their teeth and cranial features, including thicker, robust teeth with grooved tooth enamel. The analysis could indicate that whileP. sachicarum probably had a generalist diet,Muiscasaurus was a much more specialized form, feeding on smaller and softer prey items. This would show that during the Cretaceous period in theneotropics, ichthyosaurs kept some ecological diversity.[2]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||
