User:Amirani1746/sandbox7

Temnodontosaurus (meaning "cutting-tooth lizard") is an extinct genus of large ichthyosaurs that lived during the Lower Jurassic in what is now Europe and possibly Chile. The first known fossil is a specimen consisting of a complete skull and partial skeleton discovered on a cliff by Joseph and Mary Anning around the early 1810s in the Dorset county, England. The anatomy of this specimen was subsequently analyzed in a series of articles written by Everard Home between 1814 and 1819, making it the very first ichthyosaur to have been scientifically described. In 1822, the specimen was assigned to the genus Ichthyosaurus by William Conybeare, and more precisely to the species I. platyodon. Noting the large dental differences with other species of Ichthyosaurus, Richard Lydekker suggested in 1889 moving this species into a separate genus, which he named Temnodontosaurus. While many species have been assigned to the genus, only five are currently recognized as valid, the others being considered as synonymous, doubtful or possibly belonging to other taxa.

Generally estimated at 9 m long, Temnodontosaurus is one of the largest known ichthyosaurs, although not as imposing as some Triassic forms. Specimens assigned to the genus may nevertheless have reached larger measurements. As an ichthyosaur, Temnodontosaurus had flippers for limbs and a fin on the tail. Boasting eye sockets measuring more than 25 cm wide, Temnodontosaurus quite possibly had the largest eyes known in the entire animal kingdom, rivaling in size those of the colossal squid. The snout appears to be longer than the mandible, being equipped with several sharp teeth (hence its name). On the basis of numerous very complete skeletons, it is estimated that the animal had at least more than 40 presacral vertebrae. Temnodontosaurus is a basal representative of the parvipelvian subgroup, in addition to being its largest representative. A monotypic family, Temnodontosauridae, was even established in 1974 to include the genus. The various phylogenetic analyzes as well as the diagnostic problems concerning it make it for the moment a polyphyletic taxon (unnatural grouping), and therefore needs to be revised.

Discovery and identification
Temnodontosaurus is historically the very first ichthyosaur to have been scientifically described. Around 1810, a certain Joseph Anning discovered the skull of a large marine reptile on the cliffs of Black Ven, between the town of Lyme Regis and the village of Charmouth, two localities located in the county of Dorset, in the south of England. The remaining skeleton was later discovered by his sister, the now famous Mary Anning, in 1812. Although other ichthyosaur skeletons have been discovered locally and elsewhere, this particular specimen was the first to attract attention of the scientific community. After the discovery was announced in the press, the specimen was purchased by the lord of a local manor, Henry Hoste Henley, for a price of £23. Subsequently, Henley passed the fossils on to the naturalist William Bullock, who put them on display in the collections of his museum in London. In 1819, Bullock's own collection was sold to the Natural History Museum in London for a price of around £47. The specimen, now cataloged as NHMUK PV R1158, is still currently housed at this museum, although the postcranial remains have since been lost.

Beginning in 1814, Everard Home wrote a series of six papers for the Royal Society describing the specimen, initially identifying it as a crocodile. Perplexed as to the real nature of the fossil, Home kept changing his mind about its classification, thinking that it would be a fish, then as an animal sharing affinities with the platypus, which was then recently described at that time. Finally, in 1819, he thought that the fossil represented an animal that embodied an intermediate form between salamanders and lizards, which led him to erect the genus name Proteosaurus (originally written as Proteo-Saurus). In 1821, Henry De la Beche and his colleague William Daniel Conybeare made the very first scientific description of Ichthyosaurus, but did not name any species. Although being initially a nomen nudum, this generic name was already proposed in 1818 by Charles Konig, but was thus chosen as the definitive scientific name of this genus, Proteosaurus having since become a nomen oblitum. In their article, De la Beche and Conybeare refer several additional fossils discovered at Black Ven to this genus, also including the specimen originally described by Home. It was in 1822 that De la Beche named three species of Ichthyosaurus on the basis of several anatomical differences distinguishing the specimens, one of them being I. platyodon. He nevertheless announces that future descriptions will be done with the help of Conybeare. However, it was Conybeare himself who described the fossils the same year, attributing the largest specimens to I. platyodon, The specific name platyodon comes from the Ancient Greek πλατύς (platús, "flat", "broad"), and ὀδούς (odoús, "tooth"), all meaning "flat teeth", in reference to the rather distinctive dentition of this species.



In 1889, Henry Alleyne Nicholson and Richard Lydekker published a two-volume work that served as an introduction to the rules of paleontology for students. However, it is in the second volume that the two paleontologists give a very detailed description of numerous prehistoric vertebrates, and during which the taxonomy of I. platyodon takes another direction. Indeed, in his correction notes, Lydekker notices that the teeth of I. platyodon have great differences from those of other previously recognized species of Ichthyosaurus and suggest that the latter could be the type species of a completely new genus of ichthyosaurs, which he names Temnodontosaurus. This generic name is formed from the Ancient Greek τέμνω (temnō, "to cut"), ὀδούς (odoús, "tooth"), and σαῦρος (saûros, "lizard"), to give "cutting-tooth lizard". In a broad review of fossil vertebrates published in 1902, Oliver Perry Hay suggested that because the name Proteosaurus technically took precedence over Ichthyosaurus, he then displaced I. platyodon as the type species of that genus, then renamed Proteosaurus platyodon. He also erects the family Proteosauridae for this reason, relegating Ichthyosauridae as a junior synonym. In 1972, Christopher McGowan again used this combination proposed by Hay (although not mentioned), but the latter revised his judgment two years later, in 1974, in which he moved this species to Temnodontosaurus, as originally proposed by Lydekker. The holotype of Temnodontosaurus platyodon consisted basically of a single tooth which was preserved by the Geological Society of London. As the latter has since been noted as lost in 1960, McGowan designates specimen NHMUK PV R2003 as the neotype of this taxon. This specimen, already mentioned as a representative of the species by Richard Owen in 1881, was originally discovered and partly collected by Mary Anning in July 1832 in Lyme Regis. After the discovery, she sold the find to Thomas Hawkins, who himself sold the specimen to the Natural History Museum in London in 1834 for a price of £210.

Recognized species


In 1843, Carl von Theodori describes a new species of Ichthyosaurus, I. trigonodon, which he describes as "colossal", based on an imposing specimen comprising a complete skull and a partial postcranial skeleton discovered in the town of Holzmaden, in the state of Baden-Württemberg, Germany. The specific name comes from Ancient Greek τρίγωνον (trígônon, "triangle") and ὀδούς (odoús, "tooth"), in reference to the dental crown which is visibly triangular in this species. In 1854, von Theodori made a much more in-depth description of the holotype specimen. In 1889, only some time before he established the genus Temnodontosaurus, Lydekker noted that the dentition of I. trigonodon is quite similar to that of I. platyodon. Based on these dental characteristics, he moved this species to the genus Temnodontosaurus the following year, consequently being renamed T. trigonodon. It is one of the most documented species of the genus, being known from numerous very complete specimens discovered for the majority of them in Germany and France, with a possible occurrence of a large specimen discovered in England

In 1857, an almost complete skeleton of a large ichthyosaur was discovered north of the English town of Whitby, located in the Yorkshire county. The latter is also found near another skeleton, that of a pliosaur, which is today recognized as the holotype specimen of Rhomaleosaurus cramptoni. Shortly after its discovery, the ichthyosaurian skeleton was subsequently sent to the Yorkshire Museum, where it was cataloged as YORYM 497. The following year, 1858, Owen examined the specimen and classified it as distinct from I. platyodon, attributing it to a completely new species which he named I. crassimanus. However, the latter has never been scientifically described by Owen, although it is briefly mentioned in a work by John Phillips and Robert Etheridge published in 1875. It was in 1876 that John Frederick Blake made the first scientific description of the animal, although he did so only very briefly. In 1889, Lydekker considered this species as a potential junior synonym of I. trigonodon, an opinion which was followed by numerous authors until around the beginning of the 20th century. In 1930, Sidney Melmore made the first in-depth description of I. crassimanus based on the holotype specimen, restoring the distinct status of the species. In his revision published in 1974, McGowan synonymized I. crassimanus with the proposed taxon Stenopterygius acutirostis, also attributing other specimens discovered in the original locality. In 2003, McGowan and Ryosuke Motani suggested that all specimens historically attributed to I. crassimanus appeared sufficiently different from T. platyodon and T. trigonodon to belong to a distinct species of the genus Temnodontosaurus, being renamed T. crassimanus. However, they note that further research could question its validity. However, in 2020 and 2021 respectively, a thesis and a study redescribing the specimens attributed to T. crassimanus formally maintain its validity and its membership in this genus.



In 1880, Harry Govier Seeley described the species I. zetlandicus on the basis of a well-preserved skull loaned by an Earl of Shetland (hence its name) around an unspecified date to the Sedgwick Museum of Earth Sciences in Cambridge, in the Cambridgeshire county. This skull, cataloged as CAMSM J35176, was discovered in the coasts of Whitby, near the locality where T. crassimanus was already discovered. In 1922, Friedrich von Huene moved the species within Stenopterygius. In 1974, McGowan considered S. zetlandicus as a synonym of S. acutirostris, before this species was itself synonymized with T. acutirostris from 1997. In 2022, Antoine Laboury and his colleagues reestablished the validity of the species but moved it to the genus Temnodontosaurus, being renamed T. zetlandicus. In their description, they attribute another specimen to the taxon, cataloged as MNHNL TU885, a partial skull which was originally discovered in Schouweiler, southern Luxembourg.

In 1931, von Huene described a new species of the genus Leptopterygius, L. nürtingensis, based on a skull and some postcranial remains of a single specimen discovered in a quarry in the town of Nürtingen (hence its name), Baden-Württemberg, Germany. This specimen, cataloged as SMNS 13488, is mentioned for the first time in a work by Eberhard Fraas published posthumously in 1919, in which the author considers it to be the representative of an undetermined species of Ichthyosaurus. In another work also published posthumously in 1926, Fraas attributed this specimen to a proposed new species which he named I. bellicosus. Fraas was initially expected to carry out the first scientific description of this taxon, but the latter's premature death in 1915 prevented this project from being achieved. Thus, in the absence of a scientific description, the name I. bellicosus is seen as a nomen nudum, and therefore does not have priority over L. nürtingensis. Although L. nürtingensis was only officially described in 1931 by von Huene, the taxon was already mentioned a year earlier by the same author in an article concerning the ribs of the holotype specimen,, which have since been noted as lost. In 1939, Oskar Kuhn assimilated an incomplete specimen discovered in Aue-Fallstein, Lower Saxony, to this species. However, Kuhn did not present sufficient evidence to confirm his claims, and the specimen has since been viewed as indeterminate. In 1979, McGowan carried out a large revision of the ichthyosaurs known from Germany, in which he classified L. nürtingensis as a nomen dubium. In 1997, Michael W. Maisch and Axel Hungerbühler formally criticized McGowan's view, given that the holotype specimen is preserved in an excellent state of conservation and is easily diagnosable. He then redescribed this specimen and considered it to be attributable to Temnodontosaurus. In their analysis, the authors change the typography of the species nürtingensis to nuertingensis, due to rule 32.C of the ICZN requiring it. The species is again considered a nomen dubium by McGowan and Motani in 2003, but its validity as well as its belonging to this genus and maintained in subsequent studies.

Dubious species
In 1881, Owen attributed a large isolated skull discovered at Lyme Regis, cataloged as NHMUK PV R1157, to the newly erected species of the genus Ichthyosaurus, I. breviceps. In 1922, von Huene moved this species to the genus Eurypterygius, a taxon which is itself recognized as a junior synonym of Ichthyosaurus. Although I. breviceps is still recognized as belonging to this genus, the large skull historically attributed to the species has large differences with the holotype specimen. Noting this, McGowan redescribed this specimen in more detail and made it the holotype of an entirely new species of Temnodontosaurus, T. eurycephalus. The specific name comes from the Ancient Greek ευρύς (eurús, "broad"), and κεφαλή (kephalế, "head"), all meaning "broad head", in reference to the cranial morphology of the taxon.

In 1984, an almost complete skeleton of a large ichthyosaur was discovered in the Lafarge quarries in the French commune of Belmont-d'Azergues, located near Lyon. Although the specimen is mentioned in a detailed biostratigraphic analysis of the Lafarge quarries published in 1991, it was in 2012 when the fossil, uncatalogued but stored in the Saint-Pierre-la-Palud local mining museum, was officially designated as the holotype of the new species T. azerguensis by Jeremy E. Martin and his colleagues. The specific name comes from the Azergues, a river located near the site of the discovery.

In 2014, the American paleontologist Darren Naish expressed doubts in a blog in the journal Scientific American about the attribution of these two species to Temnodontosaurus, noting their large anatomical differences highlighting the need for a taxonomic revision of this genus. A similar observation is shared in the study describing T. zetlandicus in 2022, with the authors mentioning these two species as too phylogenetically unstable to be included in a monophyletic grouping of Temnodontosaurus.

Formerly assigned species


In 1892, Albert Gaudry officially described a new species of Ichthyosaurus, I. burgundiae, on the basis of a specimen discovered in the quarries of the town of Sainte-Colombe, in Yonne, France. Even before the taxon was described by Gaudry, the specimen, being one of the largest ichthyosaurs known at the time, led to it being presented at the 1889 Paris Exposition, the same exhibition for which the Eiffel Tower was built. After the end of the exhibition, the specimen was subsequently donated to the National Museum of Natural History in Paris, joining its collection on November 12, 1889, where it is still exhibited to this day. Gaudry already proposed the name of I. burgundiae at the French Academy of Sciences in 1891, but it was not until the following year that he published the first formal description of the taxon. In 1996, McGowan attributed a number of specimens discovered in Germany to this species, but moved it there to the genus Temnodontosaurus. In 1998, Maisch compared these specimens to the holotype of T. trigonodon, and suggested synonymizing T. burgundiae with the latter. Maisch's opinion is followed by McGowan and Motani in 2003, considering T. burgundiae as a junior synonym of T. trigonodon, despite slight osteological differences. The synonymy is however based only on German specimens, a new examination of the holotype specimen discovered in Sainte-Colombe having never been carried out due to its questionable state of conservation.



In 1974, McGowan described an additional species of Temnodontosaurus, T. risor, based on three skulls discovered at Lyme Regis. The specific name of this taxon comes from the Latin Risor, meaning "mockingbird". In his description, he justifies the distinction of this species via the larger orbits, the smaller maxillae and the curved snout. In 1995, the same author carried out a more in-depth revision of the three specimens attributed to this taxon. He then discovered that the characteristics he had previously judged to be distinctive were in fact stages of growth, the three specimens representing juveniles of T. platyodon.

Description
Temnodontosaurus, like other ichthyosaurs, had a long, thin snout, large eye sockets, and a tail fluke that was supported by vertebrae in the lower half. Ichthyosaurs were superficially similar to dolphins and had flippers rather than legs, and most (except for early species) had dorsal fins. Although the colour of Temnodontosaurus is unknown, at least some ichthyosaurs may have been uniformly dark-coloured in life, which is evidenced by the discovery of high concentrations of eumelanin pigments in the preserved skin of an early ichthyosaur fossil.

Size
Temnodontosaurus is one of the largest ichthyosaurs identified to date, although the different species who belongs it are not as imposing like the Triassic forms Shonisaurus, Himalayasaurus, Cymbospondylus or Ichthyotitan. It nevertheless represents the largest known ichthyosaur of the parvipelvian group. Based on different specimens, the species T. platyodon, T. trigonodon and T. crassimanus have a body size which is estimated to be around 9 m long. The ‘Rutland Sea Dragon’, a possible specimen of T. trigonodon discovered in January 2021 in the Rutland Water, near Oakham, is estimated to be slightly over 10 m long. Skull size varies between these three species. Although incomplete, the holotype specimen of T. crassimanus would have had a skull estimated to be around 1 m long. The largest known skulls of T. trigonodon and T. platyodon are 1.8 m to 1.9 m long, respectively. No body length estimates for T. zetlandicus and T. nuertingensis have currently been given. However, the measurement of their skull, reaching respectively 1 to 1.3 m in length, suggests that they are smaller representatives when compared to the three species previously mentioned.

Individual bones suggest that Temnodontosaurus may have grown to a larger size. In his extensive revision published in 1922, von Huene described a series of very imposing vertebrae from from the collections of the Banz Abbey Museum, Germany, the largest of them measuring 22 cm high. In 1996, McGowan nominally assigned the specimen to Temnodontosaurus, although without specific assignment. Based on SMNS 50000, a nearly complete skeleton of T. trigonodon, the author estimated the size of Banz's specimen at 16 m long, as Huene initially suggested. However, the estimate he proposes turns out to be exaggerated, given that the source of its size is incorrect based on the actual measurements of the specimen SMNS 50000, which is of a shorter length.

Placement within the Ichthyosauria


The majority of the currently recognized species of Temnodontosaurus were originally described as species of Ichthyosaurus,   before the type species T. platyodon was moved to a separate genus in 1889 by Lydekker. In 1974, McGowan established the family Temnodontosauridae, to which it is still the only genus recognized. Temnodontosaurus is one of the most basal post-Triassic ichthyosaurs. In the first major phylogenetic revision of ichthyosaurs, carried out in 1999 by Motani, Temnodontosaurus is placed in the Parvipelvia clade. It is this specific group of ichthyosaurs that includes all of the "fish-shaped" representatives, with the more basal ichthyosaurs having more elongated body plans. In 2000, Paul Martin Sander erected a new clade within this subgroup, which he named Neoichthyosauria. This clade notably brings together Temnodontosaurus, Suevoleviathan, Leptonectidae and Thunnosauria, the latter including all of the ichthyosaurs that lived until the Cretaceous. For reasons of classification convenience, McGowan and Motani established the superfamily Temnodontosauroidea in 2003. In their phylogenetic revision published in 2016, Ji and colleagues classify Leptonectidae within this proposed superfamily, recovering Temnodontosaurus as the latter's sister taxon. However, other classifications clearly do not follow this model, preferring to stick to the definition of Neoichthyosauria as previously mentioned.

Genus monophyly
For several decades, Temnodontosaurus was a taxon whose monophyly was rarely questioned. The current diagnostic of the genus was first established in the revision made by McGowan in 1974 based on some cranial and postcranial characteristics. However, as the cranial features of aquatic tetrapods are strongly influenced by convergent evolution, this does not seem ideal for establishing a stable taxonomy. Thus, since the late 1990s, many authors, including McGowan himself, have advocated that Temnodontosaurus needs to be revised. Additionally, numerous recent phylogenetic analyzes showing that the genus as currently defined is polyphyletic, with some historically assigned species being unrelated each other. Thus, pending future studies, Temnodontosaurus is currently seen as a wastebasket taxon including some large, more or less related neoichthyosaurians dating from the Lower Jurassic. In the last major study investigating the taxonomy of this genus, having been carried out by Laboury et al. (2022), only four species appear to form a monophyletic grouping, namely T. platyodon, T. trigonodon, T. zetlandicus and T. nuertingensis.

Below, a simplified cladogram based on a Bayesian analysis conducted by Laboury et al. (2022):

Paleobiology
With their dolphin-like bodies, ichthyosaurs were better adapted to their aquatic environment than any other group of marine reptiles. They were viviparous that gave birth to live young and were likely incapable of leaving the water. As homeotherms ("warm-blooded") with high metabolic rates, ichthyosaurs would have been active swimmers. Jurassic and Cretaceous ichthyosaurs, including Temnodontosaurus, had evolved a thunniform method of swimming rather than the anguilliform (undulating or eel-like) methods of earlier species. Temnodontosaurus, particularly the species T. trigonodon, is quite flexible in morphology for a parvipelvian, using its imposing flippers to maneuver under water.