| Muiscasaurus | |
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| Genus: | †Muiscasaurus Maxwell et al., 2015 |
| Type species | |
| †Muiscasaurus catheti Maxwell et al., 2015 | |
Muiscasaurus is an extinct genus of ophthalmosaurid Ichthyosaur that lived in modern Colombia during the Early Cretaceous. The only known species is the type Muiscasaurus catheti. [2]
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 identifying 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 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. [2]
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 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 and streamlined 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 thin premaxilla, the nasal aperture is partially divided in two ovals for a spur-shaped nasal process, 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 thin quadratojugal, the teeth were very thin and lacking of the thick enamel and the coarse striations, whereas in similar ichthyosaurs as Pervushovisaurus and Platypterygius had more robust teeth and grooves in the enamel. [2]
Muiscasaurus was described based on fossils that were classified as belonging to the Ophthalmosauridae family, which includes most of the ichthyosaurs that lived during the Jurassic and Cretaceous periods. Muiscasaurus seems particularly occupied a very basal position within the family, with respect to the subgroup composed by Platypterygius, Caypullisaurus and Brachypterygius (although the latter two genera were slightly older than Muiscasaurus itself) . [2]
Cladogram based in the phylogenetic analysis of Maxwell et al., 2015:
| Ophthalmosauridae |
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The following cladogram shows a possible phylogenetic position of Muiscasaurus in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020). [4]
| Ophthalmosauria |
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In addition to Muiscasaurus, in the Paja Formation has been recovered other kind of ichthyosaur, Kyhytysuka sachicarum ; it is distinguished of Muiscasaurus for their teeth and cranial features, including thicker, robust teeth with grooved tooth enamel. The analysis could indicate that while P. 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 the neotropics, ichthyosaurs kept some ecological diversity. [2]
Villa de Leyva, also called Villa de Leiva, is a touristic colonial town and municipality, in the Ricaurte Province, part of the Boyacá Department of Colombia. The town is a Colombian National Heritage Town and is on the tentative list for UNESCO World Heritage Sites. Villa de Leyva is located 37 kilometres (23 mi) west of the departmental capital Tunja. It is about three hours by car or bus from Bogotá.
Ophthalmosaurus is a genus of ichthyosaur known from the Middle-Late Jurassic. Possible remains from the earliest Cretaceous, around 145 million years ago, are also known. It was a relatively medium-sized ichthyosaur, measuring 4 m (13 ft) long and weighing 930–950 kg (2,050–2,090 lb). Named for its extremely large eyes, it had a jaw containing many small but robust teeth. Major fossil finds of this genus have been recorded in Europe with a second species possibly being found in North America.
Platypterygius is a historically paraphyletic genus of platypterygiine ichthyosaur from the Cretaceous period. It was historically used as a wastebasket taxon, and most species within Platypterygius likely are undiagnostic at the genus or species level, or represent distinct genera, even being argued as invalid. While fossils referred to Platypterygius have been found throughout different continents, the holotype specimen was found in Germany.
Plutoniosaurus is an extinct genus of ophthalmosaurid ichthyosaur of uncertain validity from the Early Cretaceous of the vicinity of Ulyanovsk, European Russia.
Caypullisaurus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur from the Late Jurassic to the Early Cretaceous of Argentina. Its holotype was collected from the Vaca Muerta Formation of Cerro Lotena, Neuquen, dating to the early Tithonian stage of the Late Jurassic, about 150 million years ago. Caypullisaurus was first named by Marta Fernández in 1997 and the type species is Caypullisaurus bonapartei. It was a large ichthyosaur, measuring about 7 m (23 ft) long.
Ophthalmosauridae is an extinct family of thunnosaur ichthyosaurs from the Middle Jurassic to the early Late Cretaceous worldwide. Almost all ichthyosaurs from the Middle Jurassic onwards belong to the family, until the extinction of ichthyosaurs in the early Late Cretaceous. Opthalmosaurids appeared worldwide during early Bajocian, subsequent to the disappearance of most other ichthyosaur lineages after the end of the Toarcian. Currently, the oldest known ophthalmosaurids is Mollesaurus from the early Bajocian of Argentina, as well as indeterminate remains of the same age from Luxembourg and Canada. Named by George H. Baur, in 1887, the family contains the basal taxa like Ophthalmosaurus. Appleby (1956) named the taxon Ophthalmosauria which was followed by some authors, but these two names are often treated as synonyms; Ophthalmosauridae has the priority over Ophthalmosauria. However, some researchers argue that Ophthalmosauridae should be restricted to the group typically referred to as Ophthalmosaurinae, with classic Platypterygiinae instead being referred to as Undorosauridae or Brachypterygiidae and Ophthalmosauria being used to unite these two groups.
Brachypterygius is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from the Late Jurassic of England. The type species was originally described and named as Ichthyosaurus extremus by Boulenger in 1904. Brachypterygius was named by Huene in 1922 for the width and shortness of the forepaddle, and the type species is therefore Brachypterygius extremus. The holotype of B. extremus was originally thought to be from the Lias Group of Bath, United Kingdom, but other specimens suggest it more likely came from the Kimmeridgian Kimmeridge Clay of Kimmeridge Bay, Dorset, UK.
Chacaicosaurus is a genus of neoichthyosaurian ichthyosaur known from the Middle Jurassic of Argentina. The single known specimen of this genus was excavated from the Los Molles Formation in Neuquén Province, and is housed at the Museo Olsacher under the specimen number MOZ 5803. This specimen consists of a skull, forelimb, some vertebrae, and some additional postcranial elements. The genus was named by Marta Fernández in 1994, and contains a single species, Chacaicosaurus cayi, making it the first named distinctive ichthyosaur from the Bajocian stage. It is a medium-sized ichthyosaur with a very long snout, which bears a ridge running along each side. The forelimbs of Chacaicosaurus are small and contain four main digits.
Maiaspondylus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaurs known from Northwest Territories of Canada, the Cambridge Greensand of England and the Voronezh Region of Russia.
Simbirskiasaurus is an extinct genus of ichthyosaur from the Early Cretaceous of Ulyanovsk Oblast, Russia. Its type specimen is YKM 65119, a fragmentary skull and vertebral column.
Arthropterygius is a widespread genus of ophthalmosaurid ichthyosaur which existed in Canada, Norway, Russia, and Argentina from the late Jurassic period and possibly to the earliest Cretaceous.
Athabascasaurus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from Alberta, Canada.
Sveltonectes is an extinct genus of platypterygiine ophthalmosaurid ichthyosaurs known from Ul’yanovsk region, western Russia.
Acamptonectes is a genus of ophthalmosaurid ichthyosaurs, a type of dolphin-like marine reptiles, that lived during the Early Cretaceous around 130 million years ago. The first specimen, a partial adult skeleton, was discovered in Speeton, England, in 1958, but was not formally described until 2012 by Valentin Fischer and colleagues. They also recognised a partial subadult skeleton belonging to the genus from Cremlingen, Germany, and specimens from other localities in England. The genus contains the single species Acamptonectes densus; the generic name means "rigid swimmer" and the specific name means "compact" or "tightly packed".
Leninia is an extinct genus of basal ophthalmosaurine ichthyosaur known from the late Early Cretaceous of western Russia. Leninia was first named by Valentin Fischer, Maxim S. Arkhangelsky, Gleb N. Uspensky, Ilya M. Stenshin and Pascal Godefroit in 2013 and the type species is Leninia stellans. It was named for Vladimir Lenin, one of the leaders of the Communist Revolution in Russia, but not directlу: the museum where fossils is housed is located within the Lenin Memorial and Lenin school complex in Ulyanovsk; accordingly, the generic name reflects the geohistorical location of the find.
Sisteronia is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from the 'middle' Cretaceous of southeastern England and southeastern France. It contains a single species, Sisteronia seeleyi.
Janusaurus is an extinct genus of ophthalmosaurid ichthyosaur from the Upper Jurassic Slottsmøya Member, Agardhfjellet Formation of Central Spitsbergen. The holotype consists of a partial skull and postcrania, and would have belonged to an individual measuring 3–4 m (9.8–13.1 ft) long. In 2019, Janusaurus was synonymized with Arthropterygius, though maintained as a separate species, by Nikolay Zverkov and Natalya Prilepskaya, although this synonymy was objected to later that same year by Lene Delsett and colleagues, who maintained that they were sufficiently different to warrant separate genera.
Leyvachelys is an extinct genus of turtles in the family Sandownidae from the Early Cretaceous of the present-day Altiplano Cundiboyacense, Eastern Ranges, Colombian Andes. The genus is known only from its type species, Leyvachelys cipadi, described in 2015 by Colombian paleontologist Edwin Cadena. Fossils of Leyvachelys have been found in the fossiliferous Paja Formation, close to Villa de Leyva, Boyacá, after which the genus is named. The holotype specimen is the oldest and most complete sandownid turtle found to date.
Sachicasaurus is an extinct genus of brachauchenine pliosaurid known from the Barremian of the Paja Formation, Altiplano Cundiboyacense in the Colombian Eastern Ranges of the Andes. The type species is S. vitae.
Kyhytysuka is an extinct genus of ophthalmosaurian ichthyosaur from Early Cretaceous Colombia. The animal was previously assigned to the genus Platypterygius, but given its own genus in 2021. Kyhytysuka was a mid-sized ophthalmosaurian with heterodont dentition and several adaptations suggesting that it was a macropredatory vertebrate hunter living in shallow waters. It contains a single species, Kyhytysuka sachicarum.
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