Триасс кезеңінде өмір сүрген ұзын мойынды рептилия - Tanystropheus

Extinct genus of reptiles

Tanystropheus (~ 'long' + στροφευς 'hinged') is an extinct genus of archosauromorph reptile which lived during the Triassic Period in Europe, Asia, and North America. It is recognisable by its extremely elongated neck, longer than the torso and tail combined. The neck was composed of 13 vertebrae strengthened by extensive cervical ribs. Tanystropheus is one of the most well described non archosauriform archosauromorphs, known from numerous fossils, including nearly complete skeletons. Some species within the genus may have reached a total length of , making Tanystropheus the longest non archosauriform archosauromorph as well. Tanystropheus is the namesake of the family Tanystropheidae, a clade collecting many long necked Triassic archosauromorphs previously described as "protorosaurs" or "prolacertiforms". Tanystropheus contains at least two valid species as well as fossils which cannot be referred to a specific species. The type species of Tanystropheus is T. conspicuus, a dubious name applied to particularly large fossils from Germany and Poland. Complete skeletons are common in the Besano Formation at Monte San Giorgio, on the border of Italy and Switzerland. Monte San Giorgio fossils belong to two species: the smaller T. longobardicus and the larger T. hydroides. These two species were formally differentiated in 2020 primarily on the basis of their strongly divergent skull anatomy. When T. longobardicus was first described in 1886, it was initially mistaken for a pterosaur and given the name "Tribelesodon". Starting in the 1920s, systematic excavations at Monte San Giorgio unearthed many more Tanystropheus fossils, revealing that the putative wing bones of "Tribelesodon" were actually neck vertebrae. Most Tanystropheus fossils hail from marine or coastal deposits of the Middle Triassic epoch (Anisian and Ladinian stages), with some exceptions. For example, a vertebra from Nova Scotia was recovered from primarily freshwater sediments. The youngest fossils in the genus are a pair of well preserved skeletons from the Zhuganpo Formation, a geological unit in China which dates to the earliest part of the Late Triassic (early Carnian stage). The oldest putative fossils belong to "T. antiquus", a European species from the latest part of the Early Triassic (late Olenekian stage). T. antiquus had a proportionally shorter neck than other Tanystropheus species, so some paleontologists consider that T. antiquus deserves a separate genus, Protanystropheus. The lifestyle of Tanystropheus has been the subject of much debate. Tanystropheus is unknown from drier environments and its neck is rather stiff and ungainly, suggesting a reliance on water. Conversely, the limbs and tail lack most adaptations for swimming and closely resemble their equivalents in terrestrial reptiles. Recent studies have supported an intermediate position, reconstructing Tanystropheus as an animal equally capable on land and in the water. Despite its length, the neck was lightweight and stabilized by tendons, so it would not been a fatal hindrance to terrestrial locomotion. The hindlimbs and the base of the tail were large and muscular, capable of short bursts of active swimming in shallow water. Tanystropheus was most likely a piscivorous ambush predator: the narrow subtriangular skull of T. longobardicus is supplied with three cusped teeth suited for holding onto slippery prey, while the broader skull of T. hydroides bears an interlocking set of large curved fangs similar to the fully aquatic plesiosaurs.

19th century excavations at Monte San Giorgio, a UNESCO world heritage site on the Italy Switzerland border, revealed a fragmentary fossil of an animal with three cusped (tricuspid) teeth and elongated bones. Monte San Giorgio preserves the Besano Formation (also known as the Grenzbitumenzone), a late Anisian early Ladinian lagerstätte recognised for its spectacular fossils. In 1886, Francesco Bassani interpreted the unusual tricuspid fossil as a pterosaur, which he named Tribelesodon longobardicus. Peyer's discoveries allowed Tribelesodon longobardicus to be recognised as a non flying reptile, more than 40 years after its original description. Its supposed elongated finger bones were recognized as neck vertebrae, which compared favorably with those previously described as Tanystropheus from Germany and Poland. Thus, Tribelesodon longobardicus was renamed to Tanystropheus longobardicus and its anatomy was revised into a long necked, non pterosaur reptile. Specimen PIMUZ T 2791, which was discovered in 1929, has been designated as the neotype of the species. A small but well preserved skull and neck, specimen PIMUZ T 3901, was found in the slightly younger Meride Limestone at Monte San Giorgio. Wild (1980) gave it a new species, T. meridensis, based on a set of skull and vertebral traits proposed to differ from T. longobardicus. Later reinvestigations failed to confirm the validity of these differences, rendering T. meridensis a junior synonym of T. longobardicus.

The first Tanystropheus specimens to be described were found in the mid 19th century. They included eight large vertebrae from the Upper Muschelkalk of Germany, and a partial skeleton from the Lower Keuper of Poland. These geological units occupy part of the Middle Triassic, from the latest Anisian to middle Ladinian stages. They were later regarded as Tanystropheus fossils undiagnostic relative to other species, rendering T. conspicuus a nomen dubium possibly synonymous with T. hydroides. Over 500 "Tanystropheus conspicuus" specimens have been recovered from a Lower Keuper bonebed near the Silesian village of Miedary. This is the largest known concentration of Tanystropheus fossils, more than double the number collected from Monte San Giorgio. Though the Miedary specimens are individually limited to isolated postcranial bones, they are preserved in three dimensions and show great potential for elucidating the morphology of the genus. The Miedary locality represents an isolated brackish body of water close to the coast, and the abundance of Tanystropheus fossils suggests that it was an animal well suited for this kind of habitat. In the late 1900s, Friedrich von Huene named several dubious Tanystropheus species from Germany and Poland. T. posthumus, from the Norian of Germany, was later reevaluated as an indeterminate theropod vertebra and a nomen dubium. Several more von Huene species, including "Procerosaurus cruralis", "Thecodontosaurus latespinatus", and "Thecodontosaurus primus", have been reconsidered as indeterminate material of Tanystropheus or other archosauromorphs. The Gogolin Formation ranges from the upper Olenekian (latest part of the Early Triassic) to the lower Anisian in age. Assuming they belong within Tanystropheus, the fossils of T. antiquus may be the oldest in the genus. Specimens likely referable to T. antiquus are also known from throughout Germany and the fossiliferous Winterswijk site in the Netherlands. However, this species may be dubious due to the difficulty of distinguishing its vertebrae from T. conspicuus or T. longobardicus. Another new species, T. biharicus, was described from Romania in 1975. It has also been considered possibly synonymous with T. longobardicus. A Tanystropheus like vertebra from the middle Ladinian Erfurt Formation (Lettenkeuper) of Germany was described in 1846 as one of several fossils gathered under the name "Zanclodon laevis". Though likely the first Tanystropheus fossil to be discovered, the vertebra is now lost, and surviving jaw fragments and other fossil scraps of "Zanclodon laevis" represent indeterminate archosauriforms with no relation to Tanystropheus. The most well preserved Tanystropheus fossils outside of Monte San Giorgio come from the Guizhou province of China, as described by Li (2007) and Rieppel (2010). Tanystropheus like tanystropheid fossils are known from another freshwater formation in North America: the Anisian age Moenkopi Formation of Arizona and New Mexico. Several new tanystropheid genera have been named from former Tanystropheus fossils. Fossils from the Anisian Röt Formation in Germany, previously referred to Tanystropheus antiquus, were named as a new genus and species in 2006: Amotosaurus rotfeldensis. In 2011, fossils from the Lipovskaya Formation of Russia were given the new genus and species Augustaburiania vatagini by A. G. Sennikov. He also named the new genus Protanystropheus for T. antiquus, though a few studies continued to retain that species within Tanystropheus.

The skull of Tanystropheus longobardicus is roughly triangular when seen from the side and top, narrowing towards the snout. Some individuals of T. longobardicus have tricuspid teeth along their entire maxilla, while in others up to seven maxillary teeth are single cusped fangs similar to the premaxillary teeth. Tanystropheus has 13 cervical (neck) vertebrae, most of which are massive, though the two closest to the head are smaller and less strongly developed. The tail is long, with at least 30 and possible up to 50 caudal vertebrae. The scapula (upper shoulder blade) has the form of a large semicircular plate on a short, broad stalk. It lies above the coracoid (lower shoulder blade), which is a large oval shaped plate with a broad glenoid facet (shoulder socket). sit behind the hips in about half of known specimens preserving the area. They occupy the base of the tail, a region which lacks chevrons. The Early Triassic reptile Prolacerta, from South Africa, also became involved upon its discovery. Prolacerta was the namesake of yet another term introduced into the convoluted space of reptile taxonomy: "Prolacertiformes". As the century progressed, two competing hypotheses for the affinities of Tanystropheus developed from the groundwork set by Peyer. Both hypotheses were justified by patterns of skull fenestration (the shape of holes in the skull behind the eye) and cranial kinesis (the flexibility of joints within the skull). One idea was that Tanystropheus and kin (particularly Macrocnemus and Prolacerta) were ancestral to "lacertilians", an antequated term for lizards. This hypothesis was supported up until the 1980s by German and Swiss paleontologists, including Rupert Wild, Some publications from the mid 20th century argued that "protorosaurs" were "euryapsids" (reptiles with only an upper temporal fenestra) related to sauropterygians,

In 1975, a paper by South African paleontologist C. E. Gow argued that none of these hypotheses were entirely correct. He proposed that Prolacerta, and by extension Macrocnemus and Tanystropheus, occupied an extinct spur on the reptile family tree near the ancestry of archosaurs, a diverse group of reptiles with lightweight skulls and serrated teeth set in deep sockets. Protorosaurus , and Prolacerta like species, were described in the 1970s, not long after the field of paleontology was reinvigorated by the "dinosaur renaissance" in the 1960s and beyond.

In the 1980s, the advent of cladistics saw a paradigm shift in the field of taxonomy, emphasizing monophyletic clades (all encompassing groups defined by shared ancestry) over other categorization styles. Phylogenetic analyses were invented to evaluate reptile evolution in a quantitative manner, by collecting a set of characteristics in sampled species and then using computational models to find the simplest (most parsimonious) path evolution could take to produce that character distribution. Cladistics stabilized and defined a fundamental split in the family tree of reptiles: one side of the family tree, Lepidosauromorpha, leads to lepidosaurs such as squamates (lizards and snakes) and the tuatara. The other side, Archosauromorpha, leads to archosaurs. Cladistics was one of many lines of evidence that helped to demonstrate the dinosaurian origin of birds. This left crocodilians and birds as the two surviving archosaur groups. A series of phylogenetic analyses in the late 1980s and 1990s strongly supported the proposal of Gow (1975). Tanystropheus, Macrocnemus, Protorosaurus, and Prolacerta were always placed as members of Archosauromorpha, closer to archosaurs than to squamates. "Protorosauria" and "Prolacertiformes" were used interchangeably for the archosauromorph subgroup encompassing these superficially lizard like reptiles. Some authors preferred "Protorosauria" for its priority. Most others used "Prolacertiformes" arguing that "Protorosauria" was a name that carried too much historical baggage, since it had previously encompassed non archosauromorph "euryapsids" like Araeoscelis. additionally qualify as archosauromorphs. The following cladogram is from Dilkes (1998), a study with a small sample of "prolacertiforms" but closer resemblance to most analyses of the 2000s and 2010s: These results have driven paleontologists to the conclusion that "Protorosauria" / "Prolacertiformes" is not a natural monophyletic clade and fails to adequately describe the structure of Archosauromorpha. In the modern cladistic framework, it could be considered a paraphyletic grade or polyphyletic category of archosauromorphs united by "primitive" characteristics (such as a slender neck and lizard like body) rather than a shared evolutionary history.|left]]The diet of Tanystropheus has been strongly debated in the past, though most recent studies consider it a piscivorous (fish eating) reptile.

In T. hydroides, the connection between the quadrate and squamosal is loose, with the upper extremity of the quadrate hooking into a deep concavity on the squamosal. This would have enabled a degree of flexibility along the quadrate squamosal contact, allowing the quadrate to swivel around an otic joint. This a condition is a form of cranial kinesis (movement among bones in the cranium) known as streptostyly, which is found in some living lizards. The quadrate is also loosely connected to the pterygoid, and the quadratojugal fails to contact the jugal, two qualities which allow movement of the quadrate without hindrance. While streptostyly is possible in the reconstructed skull, it cannot be demonstrated whether it was actively used by the living animal. The portion of the material at the base of the tail is particularly thick and rich in phosphate. Many small spherical structures are also present in this portion, which upon further preparation were revealed to be composed of calcium carbonate. These chemicals suggest that the black material was formed as a product of the specimen's proteins decaying in a warm, stagnant, and acidic environment. As in Macrocnemus, the concentration of this material at the base of the tail suggests that the specimen had a quite noticeable amount of muscle behind its hips. Though this interpretation is not wholly consistent with its proposed neck biomechanics, more recent arguments have supported the idea that Tanystropheus was fully capable of movement on land. Renesto (2005) supported this type of lifestyle as well. Renesto and Franco Saller's 2018 follow up to Renesto (2005) offered more information on the reconstructed musculature of Tanystropheus. This study determined that the first few tail vertebrae of Tanystropheus would have housed powerful tendons and ligaments that would have made the body more stiff, keeping the belly off the ground and preventing the neck from pulling the body over.

Tschanz (1986, 1988) suggested that Tanystropheus lacked the musculature to raise its neck above the ground, and that it was probably completely aquatic, swimming by undulating its body and tail side to side like a snake or crocodile. This interpretation has been contradicted by later studies, although Tanystropheus may have still spent a large portion of its life in shallow water. Renesto (2005) argued that Tanystropheus lacked clear adaptations for underwater swimming to the same degree as most other aquatic reptiles. The tail of Tanystropheus was compressed vertically (from top to bottom) at the base and thinned towards the tip, so it would not have been useful as a fin for lateral (side to side) movement. The long neck and short front limbs shifted the center of mass back to the long hind limbs, which would have made four limbed swimming inefficient and unstable if that was the preferred form of locomotion. He additionally claimed that thrusting with only the hind limbs, as in swimming frogs, was an inefficient form of locomotion for a large animal such as Tanystropheus. Contrary to earlier arguments, Renesto and Saller (2018) found some evidence that Tanstropheus was adapted for an unusual style of swimming. They noted that, based on reconstructions of muscle mass, the hind limbs would have been quite flexible and powerful according to muscle correlations on the legs, pelvis, and tail vertebrae. Their proposal was that Tanystropheus made use of a specialized mode of underwater movement: extending the hind limbs forward and then simultaneously retracting them, creating a powerful 'jump' forward. Further support for this hypothesis is based on the ichnogenus (trackway fossil) Gwyneddichnium, which was likely created by small tanystropheids such as Tanytrachelos. Some Gwyneddichnium tracks seem to represent a succession of paired sprawling footprints from the hind limbs, without any hand prints. These tracks may have been created by the same form of movement which Renesto and Saller (2018) hypothesized as the preferred method of swimming in Tanystropheus. Nevertheless, lateral undulation cannot be disregarded as a potential swimming style; vertebrae near the hips have extended transverse processes, which are associated with powerful undulating tail muscles in reptiles such as crocodilians. Tail movements may be more effective for swimming than paddling or thrusting with the hindlimbs, since the foot bones of Tanystropheus are narrowly bundled together with little room for webbing. The skull of Tanystropheus shows additional support for a semiaquatic habits: both T. hydroides and T. longobardicus have large undivided nares positioned on the upper surface of the snout, a location consistent with this lifestyle in other animals. In addition, the femur density approaches that of Lariosaurus, an aquatic nothosaur. When hunting underwater, Tanystropheus may have acted as an ambush predator, using its long neck to stealthily approach schools of fish or squid while keeping its large body undetected. Upon selecting a suitable prey item, it would dash forwards or snap to the side. T. hydroides was particularly well suited for lateral biting, thanks to its low skull and procumbent fangs. A methodical and intermittent approach to underwater hunting would be appropriate for Tanystropheus, considering its lack of adaptations for an exclusively aquatic life. It was likely incapable of pursuit predation, in contrast to more persistent and specialized marine reptiles such as ichthyosaurs or plesiosaurs.