Kawanectes | |
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Life restoration | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Superorder: | † Sauropterygia |
Order: | † Plesiosauria |
Family: | † Elasmosauridae |
Genus: | † Kawanectes O'Gorman 2016 |
Species: | †K. lafquenianum |
Binomial name | |
†Kawanectes lafquenianum (Gasparini & Goñi 1985) | |
Synonyms | |
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Kawanectes (meaning "Kawas swimmer") is a genus of elasmosaurid plesiosaur, a type of long-necked marine reptile, that lived in the marginal marine (probably estuarine) environment of Late Cretaceous Patagonia. It contains one species, K. lafquenianum, described in 2016 by O'Gorman. [1]
Measuring 3.8 m (12.5 ft) long, Kawanectes was small for an elasmosaurid. [1] It belongs to the "non-elongated" group of elasmosaurids, meaning that its cervical vertebrae are not extremely lengthened, neither do they show great variability in length. [2] The MCS specimen preserves 15 cervical vertebrae and 15 dorsal vertebrae, while the holotype preserves 10 caudal vertebrae; the true number of cervical and caudal vertebrae is unknown due to the incompleteness of the specimens. [1]
A combination of traits can be used to distinguish Kawanectes from all other elasmosaurids: the centra of the vertebrae are wider than they are long; the projections known as the parapophyses on the caudal vertebrae are knob-like; the ischium and pubis form a "bar" of bone that encloses two diamond-shaped openings; the ratio between the length of the humerus and the femur is unusually high (1.2); the end of the humerus bears a backward projection of bone which forms an articulating surface; and the capitulum of the femur, which likewise forms an articulating surface, is strongly convex. [1]
Although Kawanectes is similar to the somewhat-larger Vegasaurus , its bones clearly represent that of an adult due to the fusion in the vertebrae, the proportions of its cervical vertebrae are the same as Vegasaurus (if Vegasaurus was an older Kawanectes, its cervical vertebrae would be longer, [2] as with other elasmosaurids), and Vegasaurus does not have a pelvic bar (since the pelvic bar is absent in juvenile elamosaurids but present in adults, the emergence then disappearance of the pelvic bar contradicts a hypothetical growth sequence), suggesting that Vegasaurus is not the adult form of Kawanectes. [1] On the basis of three known specimens, it is proposed that the genus exhibits sexual dimorphism in terms of ilium shape, humerus to femur size ratio and sacral centrum proportions, and that females are larger than males. [3]
Kawanectes is known from the "Bentonitas Patagonicas" quarry in Rio Negro Province, Argentina. This quarry belongs to the Middle Member of the Allen Formation, which dates to the late Campanian to Early Maastrichtian of the Late Cretaceous. [4] Three specimens are known: the holotype, MLP 71-II-13-1, which consists of various parts of the axial skeleton along with a femur, a humerus, an ilium, and a foot bone; MCS PV 4, which again consists of various axial bones in addition to a scapula, part of a coracoid, both sets of ischia and pubes, part of a foot, and 389 gastroliths; and MUC Pv 92, which also contains axial elements along with a femur, two foot bones, and fragments of the limb girdles. [1] In 2020, another specimen was discovered from the La Colonia Formation. [5]
Initially recognized as a species of Trinacromerum , [6] polycotylid affinities were later rejected for "T." lafquenianum. [7] O'Gorman named the new monotypic genus Kawanectes for "T." lafquenianum in 2016. The name combines Kawa, which refers to the Kawas Sea, [8] an ancient ocean that covered Patagonia from the Campanian to the Danian, and Greek nectes, which means "swimmer". The original specific name, lafquenianum, is the Mapuche word for "sea". [1]
In 2016, a phylogenetic analysis found that Kawanectes was a close relative to, but not a member of, the Aristonectinae. [9]
Elasmosauridae |
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With the discovery of Kawanectes, the plesiosaurian fauna of the Kawas sea (which spans both the Allen Formation and the contemporary La Colonia Formation) contains all three major lineages of Late Cretaceous plesiosaurs: non-aristonectine elasmosaurids (Kawanectes and Chubutinectes [10] ), aristonectine elasmosaurids ( Aristonectes [11] ), and polycotylids ( Sulcusuchus [12] ). This is unusual, since these formations represent continental-to-marginal marine environments (i.e. not open ocean). [13] [14] These plesiosaurs appear to be generally smaller than their open-ocean counterparts at adult size. [14] [1]
Elasmosaurus is a genus of plesiosaur that lived in North America during the Campanian stage of the Late Cretaceous period, about 80.5 million years ago. The first specimen was discovered in 1867 near Fort Wallace, Kansas, US, and was sent to the American paleontologist Edward Drinker Cope, who named it E. platyurus in 1868. The generic name means "thin-plate reptile", and the specific name means "flat-tailed". Cope originally reconstructed the skeleton of Elasmosaurus with the skull at the end of the tail, an error which was made light of by the paleontologist Othniel Charles Marsh, and became part of their "Bone Wars" rivalry. Only one incomplete Elasmosaurus skeleton is definitely known, consisting of a fragmentary skull, the spine, and the pectoral and pelvic girdles, and a single species is recognized today; other species are now considered invalid or have been moved to other genera.
Futabasaurus is a genus of plesiosaur from the Late Cretaceous of Fukushima, Japan. It was described and named in 2006, and was assigned to the family Elasmosauridae. The genus contains one species, F. suzukii.
Elasmosauridae is an extinct family of plesiosaurs, often called elasmosaurs. They had the longest necks of the plesiosaurs and existed from the Hauterivian to the Maastrichtian stages of the Cretaceous, and represented one of the two groups of plesiosaurs present at the end of the Cretaceous alongside Polycotylidae.
Libonectes is an extinct genus of sauropterygian reptile belonging to the plesiosaur order. It is known from specimens found in the Britton Formation of Texas (USA) and the Akrabou Formation of Morocco, which have been dated to the lower Turonian stage of the late Cretaceous period.
Mauisaurus is a dubious genus of plesiosaur that lived during the Late Cretaceous period in what is now New Zealand. Numerous specimens have been attributed to this genus in the past, but a 2017 paper restricts Mauisaurus to the lectotype and declares it a nomen dubium.
Tuarangisaurus is an extinct genus of elasmosaurid known from New Zealand. The type and only known species is Tuarangisaurus keyesi, named by Wiffen and Moisley in 1986.
Aphrosaurus was an extinct genus of plesiosaur from the Maastrichtian. The type species is Aphrosaurus furlongi, named by Welles in 1943. The holotype specimen was discovered in the Moreno Formation in Fresno County, California in 1939 by rancher Frank C. Piava. A second specimen - LACM 2832 - was also found in the same formation and initially diagnosed as a juvenile of the same species, but has since been removed from the genus.
Aristonectes is an extinct genus of large elasmosaurid plesiosaurs that lived during the Maastrichtian stage of the Late Cretaceous. Two species are known, A. parvidens and A. quiriquinensis, whose fossil remains were discovered in what are now Patagonia and Antarctica. Throughout the 20th century, Aristonectes was a difficult animal for scientists to analyze due to poor fossil preparation, its relationships to other genera were uncertain. After subsequent revisions and discoveries carried out from the beginning of the 21st century, Aristonectes is now recognised as the type genus of the subfamily Aristonectinae, a lineage of elasmosaurids characterized by an enlarged skull and a reduced length of the neck.
Kaiwhekea is an extinct genus of plesiosaur from the Late Cretaceous of what is now New Zealand.
Brancasaurus is a genus of plesiosaur which lived in a freshwater lake in the Early Cretaceous of what is now North Rhine-Westphalia, Germany. With a long neck possessing vertebrae bearing distinctively-shaped "shark fin"-shaped neural spines, and a relatively small and pointed head, Brancasaurus is superficially similar to Elasmosaurus, albeit smaller in size at 3.26 metres (10.7 ft) in length as a subadult.
The La Colonia Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.
Alexandronectes is a genus of elasmosaurid plesiosaur, a type of long-necked marine reptile, that lived in the oceans of Late Cretaceous New Zealand. It contains one species, A. zealandiensis. Fossils of Alexandronectes were found in the Conway Formation of Canterbury, which can be dated to the Early Maastrichtian stage of the Cretaceous. Fossils of it were found around 1872 near the Waipara River, north of Christchurch, New Zealand.
Albertonectes is an extinct genus of elasmosaurid plesiosaur known from the Late Cretaceous Bearpaw Formation of Alberta, Canada. It contains a single species, Albertonectes vanderveldei. Albertonectes is the longest elasmosaur, and more generally plesiosaur, known to date both in neck and total body length.
This timeline of plesiosaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, taxonomic revisions, and cultural portrayals of plesiosaurs, an order of marine reptiles that flourished during the Mesozoic Era. The first scientifically documented plesiosaur fossils were discovered during the early 19th century by Mary Anning. Plesiosaurs were actually discovered and described before dinosaurs. They were also among the first animals to be featured in artistic reconstructions of the ancient world, and therefore among the earliest prehistoric creatures to attract the attention of the lay public. Plesiosaurs were originally thought to be a kind of primitive transitional form between marine life and terrestrial reptiles. However, now plesiosaurs are recognized as highly derived marine reptiles descended from terrestrial ancestors.
Vegasaurus is an extinct genus of elasmosaurid plesiosaur known from the Late Cretaceous Snow Hill Island Formation of Vega Island, Antarctic Peninsula. It contains a single species, Vegasaurus molyi.
Wunyelfia is a genus of elasmosaurid plesiosaur, a type of long-necked marine reptile, that lived in the oceans of Late Cretaceous Chile. It contains one species, W. maulensis.
Chubutinectes is an extinct genus of elasmosaurid plesiosaur from the Late Cretaceous La Colonia Formation of Argentina. The genus contains a single species, C. carmeloi, known from a partial skeleton and associated gastroliths.
Marambionectes is an extinct genus of weddellonectian elasmosaurid plesiosaur from the Late Cretaceous López de Bertodano Formation of Antarctica. The genus contains a single species, M. molinai, known from a partial skeleton.
Titanomachya is an extinct genus of titanosaurian sauropod dinosaur from the Late Cretaceous La Colonia Formation of Argentina. The genus contains a single species, T. gimenezi. It is a relatively small titanosaur, weighing around 7.8 tonnes.