Tanystropheus

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Tanystropheus
Temporal range: late Olenekian? – early Carnian
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Tanystropheus longobardicus 4.JPG
Restored Tanystropheus skeleton
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Family: †Tanystropheidae
Genus: †Tanystropheus
Meyer, 1852
Type species
†Tanystropheus conspicuus
nomen dubium
Von Meyer, 1855
Other species
  • †T. antiquus? Von Huene, 1907-1908
  • †T. longobardicus (Bassani, 1886)
  • †T. hydroides Spiekman et al., 2020
Synonyms
Genus synonymy
  • Macroscelosaurus Münster vide Meyer, 1852 (nomen oblitum)
  • Tribelesodon Bassani, 1886
  • Procerosaurus von Huene, 1902
Species synonymy
  • T. biharicus Jurcsák, 1975 (synonym of T. longobardicus?)
  • T. haasi Rieppel, 2001 (nomen dubium)
  • T. meridensis Wild, 1980 (synonym of T. longobardicus)

Tanystropheus (Greek τανυ~ 'long' + στροφευς 'hinged') is an extinct 6-meter-long (20 ft) reptile that dates from the Middle to Late Triassic epochs. It is recognizable by its extremely elongated neck, which measured 3 m (9.8 ft) long—longer than its body and tail combined.[1] The neck was composed of 12–13 extremely elongated vertebrae.[2] With its very long but relatively stiff neck, Tanystropheus has been often proposed and reconstructed as an aquatic or semi-aquatic reptile, a theory supported by the fact that the creature is most commonly found in semi-aquatic fossil sites wherein known terrestrial reptile remains are scarce. Fossils have been found in Europe. Complete skeletons of small individuals are common in the Besano Formation at Monte San Giorgio in Italy and Switzerland; other fossils have been found in the Middle East and China, dating from the Middle Triassic to the early part of the Late Triassic (Anisian, Ladinian, and Carnian stages).[3]

History[]

Monte San Giorgio specimens[]

Franz Nopcsa's restoration of Tribelesodon, a hypothetical long-tailed pterosaur based on misinterpreted Tanystropheus longobardicus fossils

19th century excavations at Monte San Giorgio, on the Italy-Switzerland border, revealed a fragmentary fossil of an animal with three-cusped teeth and elongated bones. Monte San Giorgio preserves the Besano Formation (also known as the Grenzbitumenzone), a Anisian-Ladinian formation recognized for its spectacular fossils.[4] In 1886, Francesco Bassani interpreted the unusual fossil as a pterosaur, which he named Tribelesodon longobardicus.[5][6] It would take more than 40 years for this misconception to be resolved. Though this holotype specimen of Tribelesodon longobardicus was destroyed in World War II, excavations by Bernhard Peyer in the late 1920s and 1930s revealed many other complete specimens from Monte San Giorgio.[6]

Peyer's discoveries allowed Tribelesodon longobardicus to be recognized as a non-flying reptile, with its supposed elongated finger bones reinterpreted as neck vertebrae. These vertebrae were compared favorable 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.[6]

Well-preserved T. longobardicus fossils continue to be recovered from Monte San Giorgio up to the present day. reviewed and redescribed all specimens known at the time via several large monographs in 1973/4 and 1980. In 2005, Dr. Silvio Renesto described a T. longobardicus specimen from Switzerland which preserved the impressions of skin and other soft tissue. Five new specimens of T. longobardicus were described by Stefania Nosotti in 2007, allowing for a more comprehensive view of the anatomy of the species.[7]

A small but well-preserved skull and neck, specimen PIMUZ T 3901, was found in the slightly younger at Monte San Giorgio. It was given a new species, T. meridensis, in 1980. The specimen was later referred to T. longobardicus, rendering T. meridensis a junior synonym of that species.[6] A 2019 revision of Tanystropheus found that T. longobardicus and T. antiquus were the only valid species in the genus.[6] In 2020, large Tanystropheus specimens from Monte San Giorgio originally assigned to T. longobardicus were given a new species, T. hydroides.[8]

Other specimens[]

The first Tanystropheus specimens to be described were several large vertebrae found in the mid-19th century. They were recovered from the Upper Muschelkalk of Germany and Lower Keuper of Poland. Though initially given the name Macroscelosaurus by Count Georg Zu Münster, the publication containing this name is lost and its genus is considered a nomen oblitum. In 1855, Hermann von Meyer supplied the name Tanystropheus conspicuus, the type species of Tanystropheus, to the fossils. They were later regarded as Tanystropheus fossils undiagnostic relative to other species, rendering T. conspicuus a nomen dubium possibly synonymous with T. hydroides.[6][9] In the 1880s, E.D. Cope named three supposed new Tanystropheus species from the southwest United States. However, these fossils were later determined to belong to theropod dinosaurs, which were given the new genus Coelophysis.[6]

In the 1900s, Friedrich von Huene named several Tanystropheus species from Germany and Poland. T. posthumus, from the Norian of Germany, was later considered an indeterminate theropod vertebra and a nomen dubium. T. antiquus, from the Gogolin Formation of Poland, was based on cervical vertebrae which were proportionally shorter than those of other Tanystropheus species. Long considered destroyed in World War II, several T. antiquus fossils were rediscovered in the late 2010s. T. antiquus is currently considered one of the few valid species of Tanystropheus. As the Gogolin Formation is upper Olenekian to lower Anisian in age, T. antiquus fossils are likely the oldest in the genus. Specimens likely referable to T. antiquus are also known from Germany and The Netherlands. Several more von Huene species, including "Procerosaurus cruralis", "Thecodontosaurus latespinatus", and "Thecodontosaurus primus", have been reconsidered as indeterminate material of Tanystropheus or other archosauromorphs.[10][6]

Tanystropheus specimens from the Makhtesh Ramon in Israel were described as a new species, T. haasi, in 2001. 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. The most complete Tanystropheus fossils outside of Monte San Giorgio come from the Guizhou province of China, as described by Li (2007) and Rieppel (2010).[2] They are also the youngest and easternmost fossils in the genus, haling from the upper Ladinian or lower Carnian Zhuganpo Formation. They include a large morphotype (T. hydroides) specimen, GMPKU-P-1527, and an indeterminate juvenile skeleton, IVPP V 14472. In 2015, a large Tanystropheus cervical vertebra was described from the Anisian to Carnian Economy Member of the Wolfville Formation, in the Bay of Fundy of Nova Scotia, Canada.[11] Indeterminate Tanystropheus remains are also known from the of Saudi Arabia and various Anisian-Ladinian sites in Spain, France?, Italy, and Switzerland. One of the youngest Tanystropheus fossils is a vertebra from the lower Carnian Fusea site in Friuli, Italy.[6]

Several new tanystropheid genera have been named from former Tanystropheus fossils. In 2006, possible Tanystropheus material from the Anisian Röt Formation in Germany was named as Amotosaurus.[12] In 2011, fossils from the of Russia were given the genus Augustaburiana by A.G. Sennikov. He also named the new genus Protanystropheus for T. antiquus,[13] but other authors continue to keep that species within Tanystropheus. Tanystropheus fossai, from the Norian-age in Italy, was given its own genus Sclerostropheus in 2019.[6]

Anatomy[]

MSNM BES SC 1018, a small morphotype (T. longobardicus) specimen

By far the most recognizable feature of Tanystropheus is its hyperelongate neck, equivalent to the combined length of the body and tail.[14] The neck was composed of 12–13 hyperelongate cervical vertebrae.[2] Cervical elongation reached its peak with cervical vertebra 9, which was ten times longer than it was tall. Weak development of cervical spines suggest that epaxial musculature was underdeveloped in Tanystropheus and that intrinsic back muscles (e.g., m. longus cervicis) were the driving force behind neck movement.[14] Subvertical placement of the pre- and postzygapophyses suggested limited lateral movement of the neck, whereas cervical ribs extending off these vertebrae would have formed a ventral brace that would transmit the forces from the weight of head and neck down to the pectoral girdle, providing passive support by limiting dorsoventral flexion.[15] The body contained 13 hourglass-shaped dorsal vertebrae, two sacral vertebrae and approximately twelve caudal vertebrae with weakly developed dorsal and haemal spines along with well-developed transverse processes.[14][16]

The pectoral and pelvic girdles are notably distinct. The forelimbs are smaller and more gracile than the hindlimbs, suggesting that the center of mass for Tanystropheus was closer towards the pelvic girdle. Attachment sites for the m. caudofemoralis muscle complex, coupled with soft-tissue preservation of relative muscle size, further support the proposition that Tanystropheus was a fairly bottom-heavy animal.[14]

Paleoecology[]

PIMUZ T 2817, a large morphotype (T. hydroides) specimen

Diet[]

The diet of Tanystropheus has been controversial in the past, although most recent studies consider it a piscivorous (fish-eating) reptile. The teeth at the front of the narrow snout were long, conical, and interlocking, similar to those of nothosaurs and plesiosaurs. This was likely an adaptation for catching aquatic prey. Additionally, hooklets from cephalopod tentacles and what may be fish scales have been found near the belly regions of some specimens, further support for a piscivorous lifestyle.[7]

However, small specimens of the genus possess an additional, more unusual form of teeth. This form of teeth, which occurred in the rear part of the jaws behind the interlocking front teeth, were tricuspid (three-pronged), with a long and pointed central cusp and smaller cusps in front of and behind the central cusp. Wild (1974) considered these three-cusped teeth to be an adaptation for gripping insects. Cox (1985) noted that marine iguanas also had three-cusped teeth, and that Tanystropheus likely fed on marine algae like that species of lizard. Taylor (1989) rejected both of these hypotheses, as he considered the neck of Tanystropheus to be too inflexible for the animal to be successful at either diet.[7]

The single-cusped skull of PIMUZ T 2819, a large morphotype (T. hydroides) specimen

The most likely function of these teeth, as explained by Nosotti (2007), was that they assisted the piscivorous diet of the reptile by helping to grip slippery prey such as fish or squid. Several modern species of seals, such as the hooded seal and crabeater seal, also have multi-cusped teeth which assist their diet to a similar effect.[7] Similar teeth patterns have also been found in the pterosaur Eudimorphodon and the fellow tanystropheid Langobardisaurus, both of whom are considered piscivores. Large individuals of Tanystropheus, over 2 meters (6.6 ft) in length, lack these three-cusped teeth, instead possessing typical conical teeth at the back of the mouth. They also lack teeth on the pterygoid and palatine bones on the roof of the mouth, which possess teeth in smaller specimens. The two morphotypes were originally considered to represent juvenile and adult specimens of T. longobardicus. However, histology of the small specimens and restudy of the large specimens has shown that they each represent adult forms of two different species. The larger one-cusped morphotype was given a new species, T. hydroides, while the smaller tricuspid morphotype retained the name T. longobardicus.[8]

Soft tissue[]

Life reconstruction of Tanystropheus longobardicus

The specimen described by Renesto in 2005 displayed an unusual "black material" around the rear part of the body, with smaller patches in the middle of the back and tail. Although most of the material could not have its structure determined, the portion just in front of the hip seemingly preserved scale impressions, indicating that the black material was the remnants of soft tissue. The scales seem to be semi-rectangular and do not overlap with each other, similar to the integument reported in a juvenile Macrocnemus described in 2002.[17] 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.[14]

Lifestyle[]

The lifestyle of Tanystropheus is controversial, with different studies favoring a terrestrial or aquatic lifestyle for the animal. In the 1980s, various studies determined that Tanystropheus lacked the musculature to raise its neck above the ground, and that it was likely completely aquatic, swimming by undulating its body and tail side-to-side like a snake or crocodile.

However, in 2005 Renesto found that Tanystropheus lacked many aquatic adaptations. Although the tail of Tanystropheus was flattened, it was compressed from top-to-bottom, so that it would have been useless for side-to-side movement. The long neck and short front limbs compared to the long hind limbs would have made four-limbed swimming inefficient and unstable if that was the preferred form of locomotion. Thrusting with only the hind limbs, as in swimming frogs, was also considered an inefficient form of locomotion for a large animal such as Tanystropheus, although a later study found support for this hypothesis. Renesto's study also found that the neck was lighter than previously suggested, and that the entire front half of the body was more lightly-built than the rear half, which would have possessed a large amount of muscle mass. In addition to containing powerful hind limb muscles, this unusually large muscle mass would have shifted the animal's weight to its rear, stabilizing the animal as it swung and maneuvered its massive neck.[14]

Renesto's analysis was the basis for later analyses of the genus. In 2015, paleoartist Mark Witton concluded that, although the neck made up half of the entire animal's length, it made up only 20% of the entire animal's mass due to having light and hollow vertebrae. In comparison, the heads and necks of pterosaurs of the family Azhdarchidae made up almost 50% of the animal's mass, yet they were clearly land based carnivores. The animal is also poorly equipped for aquatic life, with the only adaptation being a lengthened fifth toe, which suggests that it visited the water some of the time, though was not wholly dependent on it. This same research has also shown that Tanystropheus would have hunted prey like a heron.[18][19] This interpretation is supported by taphonomic evidence, which indicates that the preservation of Tanystropheus specimens is more similar to the terrestrial Macrocnemus than the aquatic Serpianosaurus where all three co-occur.[20]

Tanystropheus (11) and other Early Triassic and Middle Triassic marine predators[21]

Renesto and Franco Saller's 2018 follow-up to Renesto (2005)'s study 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. In addition, the hind limbs would have been quite flexible and powerful according to muscle correlations on the legs, pelvis, and tail vertebrae. This analysis shows that Tanystropheus was capable of a specific mode of movement while swimming. Namely, a Tanystropheus could extend its hind limbs forward and then simultaneously retract them, creating a powerful 'jump' forward. Further support for this hypothesis lies in the fact that a close relative of Tanystropheus, likely the small Tanytrachelos, is believed to have left an ichnogenus (trackway fossil) called Gwyneddichnium. Some Gwyneddichnium tracks seem to represent a succession of paired footprints that can be assigned to the hind limbs, but with no hand prints. These tracks were almost certainly created by the same form of movement which Renesto and Saller theorized was the preferred form of swimming in Tanystropheus.[22]

With this information, the most likely lifestyle for Tanystropheus was that the animal was a shallow-water predator that used its long neck to stealthily approach schools of fish or squid without disturbing its prey due to its large body size. Upon selecting a suitable prey item, it would have dashed forward by propelling itself along the seabed or through the water, with both hind limbs pushing off at the same time. However, this style of swimming is most common in amphibious creatures such as frogs, and likewise Tanystropheus would also have been capable of walking around on land. The idea that Tanystropheus evolved this form of swimming over much more efficient, yet specialized, styles is evidence that it did not live an exclusively aquatic life as in most other marine reptiles such as ichthyosaurs or plesiosaurs.[22]

A 2020 digital reconstruction of Tanystropheus skulls suggested that the animals, especially the Tanystropheus hydroides, lived primarily in the water because of the position of the nostrils.[8]

Media depictions[]

Tanystrophus was depicted in the 2003 BBC TV series Sea Monsters: A Walking with Dinosaurs Trilogy (Chased by Sea Monsters in the United States).[23]

References[]

  1. ^ Elbein, Asher (12 August 2020). "Making Sense of 'One of the Most Baffling Animals That Ever Lived' - Important mysteries have been solved about a reptile with a giraffe-like neck that hunted prey 242 million years ago". The New York Times. Retrieved 14 August 2020.
  2. ^ a b c Rieppel, Olivier; Jiang, Da-Yong; Fraser, Nicholas C.; Hao, Wei-Cheng; Motani, Ryosuke; Sun, Yuan-Lin; Sun, Zuo-Yu (2010). "Tanystropheus cf. T. Longobardicus from the early Late Triassic of Guizhou Province, southwestern China". Journal of Vertebrate Paleontology. 30 (4): 1082–1089. doi:10.1080/02724634.2010.483548. JSTOR 40864387. S2CID 86315078.
  3. ^ Dal Sasso, C. and Brillante, G. (2005). Dinosaurs of Italy. Indiana University Press. ISBN 0-253-34514-6, ISBN 978-0-253-34514-1.
  4. ^ Tanystropheus. Vertebrate Palaeontology at Milano University. Retrieved 2007-02-19.
  5. ^ von Arthaber, G. (March 1922). "Über Entwicklung, Ausbildung und Absterben der Flugsaurier". Palaeontologische Zeitschrift (in German). 4 (1): 1–47. doi:10.1007/BF03041557. S2CID 131644821.
  6. ^ a b c d e f g h i j Spiekman, Stephan N. F.; Scheyer, Torsten M. (2019-12-16). "A taxonomic revision of the genus Tanystropheus (Archosauromorpha, Tanystropheidae)". Palaeontologia Electronica. 22 (3): 1–46. doi:10.26879/1038. ISSN 1094-8074.
  7. ^ a b c d Nossotti, Stefania (2007). "Tanystropheus longobardicus (Reptilia Protorosauria): Re-interpretations of the anatomy based on new specimens from the Middle Triassic of Besano (Lombardy, northern Italy)". Memorie della Societa Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano. 35 (3).
  8. ^ a b c Spiekman, Stephan N. F.; Neenan, James M.; Fraser, Nicholas C.; Fernandez, Vincent; Rieppel, Olivier; Nosotti, Stefania; Scheyer, Torsten M. (2020-08-06). "Aquatic Habits and Niche Partitioning in the Extraordinarily Long-Necked Triassic Reptile Tanystropheus". Current Biology. 30 (19): 3889–3895.e2. doi:10.1016/j.cub.2020.07.025. ISSN 0960-9822. PMID 32763168. S2CID 221012988.
  9. ^ Spiekman, Stephan N. F.; Neenan, James M.; Fraser, Nicholas C.; Fernandez, Vincent; Rieppel, Olivier; Nosotti, Stefania; Scheyer, Torsten M. (2020-11-20). "The cranial morphology of Tanystropheus hydroides (Tanystropheidae, Archosauromorpha) as revealed by synchrotron microtomography". PeerJ. 8: e10299. doi:10.7717/peerj.10299. ISSN 2167-8359. PMC 7682440. PMID 33240633.
  10. ^ Skawiński, Tomasz; Ziegler, Maciej; Czepiński, Łukasz; Szermański, Marcin; Tałanda, Mateusz; Surmik, Dawid; Niedźwiedzki, Grzegorz (2017-05-19). "A re-evaluation of the historical 'dinosaur' remains from the Middle-Upper Triassic of Poland". Historical Biology. 29 (4): 442–472. doi:10.1080/08912963.2016.1188385. ISSN 0891-2963. S2CID 133166493.
  11. ^ Sues, Hans-Dieter; Olsen, Paul E. (2015). "Stratigraphic and temporal context and faunal diversity of Permian-Jurassic continental tetrapod assemblages from the Fundy rift basin, eastern Canada" (PDF). Atlantic Geology. 51: 139–205. doi:10.4138/atlgeol.2015.006. S2CID 17520371. Archived from the original (PDF) on 8 March 2019.
  12. ^ Fraser, N. C.; Rieppel, O. (2006). "A new protorosaur (Diapsida) from the Upper Buntsandstein of the Black Forest, Germany". Journal of Vertebrate Paleontology. 26 (4): 866. doi:10.1671/0272-4634(2006)26[866:ANPDFT]2.0.CO;2.
  13. ^ Sennikov, A. G. (2011). "New tanystropheids (Reptilia: Archosauromorpha) from the Triassic of Europe". Paleontological Journal. 45 (1): 90–104. doi:10.1134/S0031030111010151. S2CID 85193597.
  14. ^ a b c d e f Renesto, S. (2005). "A new specimen of Tanystropheus (Reptilia, Protorosauria) from the Middle Triassic of Switzerland and the ecology of the genus". Rivista Italiana di Paleontologia e Stratigrafia. 111 (3): 377–394.
  15. ^ Tschanz, K. 1988. Allometry and Heterochrony in the Growth of the Neck of Triassic Prolacertiform Reptiles. Paleontology. 31:997–1011.
  16. ^ Wild, R. 1973. Tanystropheus longbardicus (Bassani) (Neue Egerbnisse). in Kuhn-Schnyder, E., Peyer, B. (eds) — Triasfauna der Tessiner Kalkalpen XXIII. Schweiz. Paleont. Abh. Vol. 95 Basel, Germany.
  17. ^ Renesto, Silvio; Avanzini, Marco (2002). "Skin remains in a juvenile Macrocnemus bassanii Nopsca (Reptilia, Prolacertiformes) from the Middle Triassic of Northern Italy". Neues Jahrbuch für Geologie und Paläontologie. 224 (1): 31–48. doi:10.1127/njgpa/224/2002/31.
  18. ^ Witton, Mark (13 November 2015). "Mark Witton.com Blog: The lifestyle of Tanystropheus, part 1: was that neck too heavy for use on land?". Retrieved 23 September 2018.
  19. ^ Witton, Mark (11 December 2015). "Mark Witton.com Blog: The lifestyle of Tanystropheus, part 2: coastal fisher or first-day-on-the-job aquatic predator?". Retrieved 23 September 2018.
  20. ^ Beardmore, S.R.; Furrer, H. (2017). "Land or water: using taphonomic models to determine the lifestyle of the Triassic protorosaur Tanystropheus (Diapsida, Archosauromorpha)". Palaeobiodiversity and Palaeoenvironments. 98 (2): 243–258. doi:10.1007/s12549-017-0299-7. S2CID 133762329.
  21. ^ Scheyer et al. (2014): Early Triassic Marine Biotic Recovery: The Predators' Perspective. PLoS ONE https://doi.org/10.1371/journal.pone.0088987
  22. ^ a b Renesto, Silvio; Saller, Franco (2018). "EVIDENCES FOR A SEMI AQUATIC LIFE STYLE IN THE TRIASSIC DIAPSID REPTILE TANYSTROPHEUS". Rivista Italiana di Paleontologia e Stratigrafia (Research in Paleontology and Stratigraphy). 124 (1): N. 1 (2018). doi:10.13130/2039-4942/9541. ISSN 2039-4942.
  23. ^ "Sea Monsters: A Walking With Dinosaurs Trilogy". BBC.

Bibliography[]

  • George Olshevsky expands on the history of "P." exogyrarum, on the Dinosaur Mailing List
  • Huene, 1902. "Übersicht über die Reptilien der Trias" [Review of the Reptilia of the Triassic]. Geologische und Paläontologische Abhandlungen. 6, 1-84.
  • Fritsch, 1905. "Synopsis der Saurier der böhm. Kreideformation" [Synopsis of the saurians of the Bohemian Cretaceous formation]. Sitzungsberichte der königlich-böhmischen Gesellschaft der Wissenschaften, II Classe. 1905(8), 1-7.
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