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Plateosaurus
Fossil range: Late Triassic, 216-199 Ma
Plateosaurus BW
Restoration of two Plateosaurus engelhardti.
Scientific classification

Class

Reptilia

Superorder

Dinosauria

Order

Saurischia

Suborder

Sauropodomorpha

Infraorder

Prosauropoda

Family

Plateosauridae

Genus

Plateosaurus
von Meyer, 1837

Species

Synonyms

  • Zanclodon Plieninger, 1846
  • Dimodosaurus Pidancet & Chopard, 1862
  • Dinosaurus Rutimeyer, 1856
  • Gresslyosaurus Rutimeyer, 1856
  • Pachysaurops Huene, 1961
  • Pachysaurus Huene, 1907-1908
  • Pachysauriscus Kuhn, 1959

Plateosaurus (meaning 'flat lizard') is a genus of plateosaurid prosauropod dinosaur that lived during the Norian and Rhaetian stages of the Late Triassic period, around 216 to 199 million years ago in what is now Europe. There are two currently recognized species, P. engelhardti and P. longiceps, although others have been assigned in the past.

Discovered in 1834 and described three years later, Plateosaurus was one of the first dinosaurs formally named, although not one of the three genera originally used to define Dinosauria, because at the time it was poorly known and impossible to identify as a dinosaur. Plateosaurus were bulky bipedal herbivores which had small skulls on long necks, sharp plant-crushing teeth, powerful limbs, and large thumb claw on each 'hand' probably used for defense and feeding.

DescriptionEdit

Human-plateosaurus size comparison(V2)

Size comparison between Plateosaurus and a human.

Plateosaurus was the largest known dinosaur of its time, reaching Template:Convert/to in length[1] and up to an estimated Template:Convert/kg in mass. A member of the group of early herbivores known as prosauropods, it was more powerfully built than that of similar animals such as Anchisaurus. Plateosaurus had a long neck, composed of around nine cervical vertebrae, a stocky body and a pear-shaped torso. It had a long tail composed of at least forty caudal vertebrae which served to counterbalance the front-heavy body and long neck.

The skull of Plateosaurus was deeper than that of most prosauropods, although still small and narrow compared to the size of its body. It had four sets of fenestrae (skull openings); these openings were for the naris and orbit as well as an infratemporal fenestra at the back of the skull and an antorbital fenestra between the eye and nose. It had a long snout and many small, leaf-shaped, socketed teeth and the low-slung hinge of its lower jaw, which give the muscles greater leverage. These features suggest that it fed exclusively on plants.[2] Its eyes were directed to the sides, rather than the front, providing all-round vision to watch for predators. Some fossil skeletons have preserved sclerotic rings.

Plateosaurus skull

Plateosaurus skull

Plateosaurus had numerous small teeth in both the upper and lower jaw, five to six on the premaxilla, twenty four to thirty on the maxilla, and twenty one to twenty eight on the dentary. These teeth had serrated, leaf-shaped crowns suitable for digestion of plant material. It is thought Plateosaurus had narrow cheek pouches which kept food from spilling out when it ate.

Discovery and historyEdit

Sketch plateosaurus

A Plateosaurus sketch by Tim Bekaert.

In 1834, physician Johann Friedrich Engelhardt discovered some vertebrae and leg bones at Heroldsberg near Nuremberg, Germany. Three years later German palaeontologist Hermann von Meyer designated them as the type specimen of his new genus, Plateosaurus.[3] This name is derived from the Greek words πλατυς/platys ('broad' or 'flat') which is derived as well from πλατη/platé ('flat surface'), and σαυρος ('lizard'),[4] which refers to the animal's flat bones and reptilian nature. The type species was named in honor to its discoverer.[3]

Between the 1910s and 1930s, excavations in a clay pit at Saxony-Anhalt dug up between 39 and 50 skeletons that belonged to Plateosaurus, Liliensternus and Halticosaurus. Some of this material was assigned to P. longiceps, which was described by paleontologist Otto Jaekel in 1914.[5] At the same time, bonebeds at Trossingen revealed several remains of Plateosaurus, most of which were designated to species now dubious or invalid.[6]

In 1997, workers of an oil platform of the Snorre oilfield located at the northern end of the North Sea, were drilling through sandstone for oil exploration when they stumbled upon a long cylinder of rock, drilled out at 2,256 meters below the seafloor. This cylinder contained a fossil which they believed was plant material. In 2003, the specimen was sent to Jørn Harald Hurum, paleontologist at the University of Oslo for study. After consulting paleontologists of the University of Bonn, they, with microscopic examination, concluded that the rock preserved fibrous bone tissue located within a crushed knucklebone which they identified as belonging to Plateosaurus,[7] making it the first dinosaur found in Norway and the deepest in the world.[8]

In August 2007, an amateur paleontologist unearthed a mass grave of dinosaurs near Frick, Switzerland, comprised of around 300 bones, in which two Plateosaurus individuals were discovered. Martin Sander, paleontologist at the University of Bonn, indicated the area could extend for 1.5 kilometers, making it the biggest fossil site in Europe. There is an estimate of one dinosaur per 100 square meters.[9]

ClassificationEdit

Scheletro dinosauro - Museo di storia naturale, Milano

Mounted cast of a Plateosaurus engelhardti skeleton.

Plateosaurus was the first prosauropod to be described, and is the type genus of the family Plateosauridae, to which gives its name. At the beginning, when the genus was poorly known, it was only included in Sauria, with the possibility of being any kind of reptile.[3] In 1845, Von Meyer created the group Pachypodes (now unused) to include Plateosaurus, Iguanodon, Megalosaurus and Hylaeosaurus,[10] however, Dinosauria (technically the same as Pachypodes) already existed. Plateosauridae was proposed by Othniel Charles Marsh in 1895 within Theropoda.[11] Years later, it was moved to Prosauropoda by Huene,[12] and was accepted by most authors.[13][14] For many years the clade only included Plateosaurus, but recently two more genera, Sellosaurus[15] and possibly Unaysaurus,[16] have been recognized.

SpeciesEdit

Valid and reassigned species Edit

Only two of the many species assigned to this genus are still considered valid. P. engelhardti, the type species, is known from at least ten skulls and more than 100 fragmentary to complete skeletons, mainly from Bavaria, Germany. The second and best-known species, P. longiceps, is based on three of 50 specimens from the Knollenmergel site at Germany. P. longiceps differs from P. engelhardti in having a longer snout and limbs, with a much lighter body structure.[17] A third species, P. gracilis lacks certain features of the genus Plateosaurus and has been placed in its own genus Sellosaurus.[17] Other species like P. trossingensis, P. fraasianus and P. integer turned out to be synonyms of P. longiceps.[6]

Dubious species Edit

Several Plateosaurus species are considered to be nomina nuda ('naked names') or nomina dubia ('doubtful names') due to their fragmentary nature and poor preservation. Species like P. erlenbergiensis are difficult to determine because the holotype lacks the sacrum, ilium and proximal pubis, which are important bones in the comparison with well-known species.[6]

Provenance Edit

Plateosaurus ottoneum

Mounted skeleton of Plateosaurus at the Ottoneum Museum of Natural Science in Kassel, Germany.

Plateosaurus is the best known of the prosauropods and one of the most common dinosaur fossils. More than 100 specimens and dozens of well-preserved skeletons have been unearthed in over 50 locations on Triassic sandstones all over western Europe. However the vast majority of fossil material belongs to P. longiceps, that unlike P. engelhardti (which is known only from Germany), has been found in more areas of Germany, France, Switzerland, and especially Greenland.[17] It was thought that specimens found at the Fleming Fjord Formation in Greenland belonged to P. engelhardti,[18] but later the material was re-studied and shifted to P. longiceps.[6]

Paleoecology Edit

In some locations, groups of complete individual fossils have been found, indicating that herds traveled together through the Triassic arid desert-like landscape of Europe, searching for new feeding and habitable grounds. They lived alongside similar prosauropod dinosaur Sellosaurus, medium-sized theropods Liliensternus and Halticosaurus, and the tiny theropod dinosaur Procompsognathus, among other contemporaries like the earliest known turtles Proganochelys, temnospondyl amphibians, aetosaurs, primitive mammals, pterosaurs, sphenodontids and fish.[19]

An alternative explanation for the numerous finds of fossils, however, is that solitary individuals inhabited dry, upland areas. When they died, their bodies would have been washed away in periodic flash floods that are typical of desert environments even today. Many individual corpses could have piled up at the end of well-worn flood channels formed at the edge of desert basins.[2]

PaleobiologyEdit

Plateosaurus was an obscure dinosaur up until the past century, with very scant material known and few detailed studies. Over time, new discoveries and researches have given researchers more information about its locomotion, feeding mechanisms and metabolism.

Feeding and dietEdit

Prosauropods such as Plateosaurus may have been herbivorous or omnivorous. As recently as the 1980s, paleontologists debated the possibility of carnivory in prosauropods.[20][21] However, the hypothesis of carnivorous prosauropods has been discredited, and all recent studies favor a herbivorous or omnivorous lifestyle for these animals. Galton and Upchurch (2004) found that cranial characteristics (such as jaw articulation) of most prosauropods are closer to those of herbivorous reptiles than those of carnivorous ones, and the shape of the tooth crown is similar to those of modern herbivorous or omnivorous iguanas. The maximum width of the crown was greater than that of the root, resulting in a cutting edge similar to those of extant herbivorous or omnivorous reptiles.[22] Barrett (2000) proposed that prosauropods supplemented their herbivorous diets with small prey or carrion.[23] Like its relative Massospondylus, it might have swallowed gastroliths (gizzard stones) to digest food because of its relatively limited ability to deal with food orally.

Posture and gaitEdit

Plateosaurus Museo del Jurásico de Asturias

Plateosaurus at the Museo del Jurásico de Asturias.

Like all prosauropods, Plateosaurus had forelimbs which were much shorter than the hindlimbs and they had distinct digits ('fingers') and a spiked 'thumb'. Plateosaurus has been traditionally depicted as quadrupedal, but a 2007 anatomical study of the forelimbs demonstrated that their range of motion precluded effective habitual quadrupedal gait. Like theropods, Plateosaurus and other related prosauropods could not rotate the hand so that their palms faced downward, and so would have been unable to use the front limbs for standing or walking. The study also ruled out the possibility of "knuckle-walking" and other forms of locomotion that would avoid the issue of the limited ability of Plateosaurus to pronate its hands.[24] Thus, although its mass suggests a quadrupedal nature, it would have been restricted to its hind legs for locomotion. The forelimbs may have been used to rake trees for food, for grasping or for defense.[24]

The hand bones of Plateosaurus were large, and bore five digits. The last two digits on each hand were very small.

MetabolismEdit

A recent analysis of fossil deposits reveals there was considerable variation in size in individuals.[1] Furthermore, growth rings in bone suggests periods of varying growth which may relate to the surrounding environment. Some plateosaurs reached their maximum size at twelve years old, while others were still growing after more than two decades. The size of adult specimens varies too; there are smaller specimens which when fully grown were four to six meters long, and others that measured up to ten meters long. The bone histology of Plateosaurus is well-preserved and studied. However, due to the absence of individuals smaller than 4.8 meters long, it is not possible to deduce an ontogenetic series for Plateosaurus. Like many other dinosaurs, Plateosaurus exhibits high growth rates, suggesting an advanced dinosaurian physiology. The paper's authors propose that the metabolism of Plateosaurus may have been intermediate between a reptilian and a warm-blooded one.

IMG 2477

WWD Plateosaurus

In Popular CultureEdit

  • In the television series Walking with Dinosaurs, Plateosaurus was seen at the end of the first episode New Blood.

ReferencesEdit

  1. ^ a b Sander, M., and Klein, N. (2005). Developmental plasticity in the life history of a prosauropod dinosaur. Science 16 December 2005:1800-1802.
  2. ^ a b Cox, Barry, R.J.G. Savage, et al.. (1999). Encyclopedia of Dinosaurs & prehistoric creatures. 14 July 2007:pg 124.
  3. ^ a b c Von Meyer, H. (1837). Mitteilung an Prof. Bronn (Plateosaurus engelhardti). Neues Jahrbuch für Geologie und Paläontologie 316. [German]
  4. ^ Liddell & Scott (1980). Greek-English Lexicon, Abridged Edition. Oxford University Press, Oxford, UK. ISBN 0-19-910207-4. 
  5. ^ Jaekel, O. (1913-14). Über die Wirbeltierfunde in der oberen Trias von Halberstadt. Paläontologische Zeitschrift 1:155-215. [German]
  6. ^ a b c d P. M. Galton. 2001. The prosauropod dinosaur Plateosaurus Meyer, 1837 (Saurischia: Sauropodomorpha; Upper Triassic). II. Notes on the referred species. Revue Paléobiologie, Genève 20(2):435-502
  7. ^ Hurum, J.H., Bergan, M., Müller, R., Nystuen, J.P., and Klein, N. (2006). A Late Triassic dinosaur bone, offshore Norway. Norwegian Journal of Geology 86:117-123. http://www.geologi.no/data/f/0/08/70/8_22301_0/117-123_NGT_print-3.pdf
  8. ^ Oil Drillers Strike World's Deepest Dinosaur
  9. ^ Dinosaur mass grave discovered in Switzerland
  10. ^ H. v. Meyer. 1845. System der fossilen Saurier [Taxonomy of fossil saurians]. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrfakten-Kunde 1845:278-285
  11. ^ O. C. Marsh. 1895. On the affinities and classification of the dinosaurian reptiles. American Journal of Science 50(300):483-498
  12. ^ F. v. Huene. 1926. On several known and unknown reptiles of the order Saurischia from England and France. Annals and Magazine of Natural History, series 9 17:473-489
  13. ^ C.-C. Young. 1941. A complete osteology of Lufengosaurus huenei Young (gen. et sp. nov.) from Lufeng, Yunnan, China. Palaeontologia Sinica, New Series C, Whole Series No. 121 7:1-59
  14. ^ J. F. Bonaparte. 1971. Los tetrápodos del sector superior de la Formación Los Colorados, La Rioja, Argentina (Triásico Superior) [The tetrapods of the upper part of the Los Colorados Formation, La Rioja, Argentina (Upper Triassic)]. Opera Lilloana 22:1-183
  15. ^ F. v. Huene. 1905. Trias-Dinosaurier Europas [European Triassic dinosaurs]. Deutschen Geologischen Gesellschaft 1905(17):345-349
  16. ^ L. A. Leal, S. A. K. Azevedo, A. W. A. Kellner and A. A. S. Da Rosa. 2004. A new early dinosaur (Sauropodomorpha) from the Caturrita Formation (Late Triassic), Paraná Basin, Brazil. Zootaxa 690:1-24
  17. ^ a b c Galton, P.M., and Upchurch, P. (2004). "Prosauropoda". in Weishampel, D.B., Dodson, P., and Osmólska, H.. The Dinosauria (2nd Edition). University of California Press. p. 235. ISBN 0-520-24209-2. 
  18. ^ F. A. Jenkins, Jr., N. H. Shubin, W. W. Amaral, S. M. Gatesy, C. R. Schaff, L. B. Clemmensen, W. R. Downs, A. R. Davidson, N. Bonde and F. Osbaeck. 1994. Late Triassic continental vertebrates and depositional environments of the Fleming Fjord Formation, Jameson Land, East Greenland. Meddelelser om Grønland, Geoscience 32:1-25
  19. ^ Lucas, S. G., 1998. Global Triassic tetrapod biostratigraphy and biochronology. Palaeogeography, Palaeoclimatology, Palaeoecology 143: 347-384.
  20. ^ Cooper, M.R. (1980). "The prosauropod dinosaur Massospondylus carinatus Owen from Zimbabwe: its biology, mode of life and phylogenetic significance". Occasional Papers of the National Museums and Monuments of Rhodesia, Series B, Natural Sciences 6 (10): 689–840. 
  21. ^ Attridge, J.; A.W. Crompton and Farish A. Jenkins, Jr. (1985). "The southern Liassic prosauropod Massospondylus discovered in North America". Journal of Vertebrate Paleontology 5 (2): 128–132. 
  22. ^ Galton, P.M. and Upchurch, P. (2004). "Prosauropoda". Weishampel & als: The Dinosauria (2nd edition), pp. 232–258.
  23. ^ Barrett, P.M. (2000). "Prosauropod dinosaurs and iguanas: Speculations on the diets of extinct reptiles". in Hans-Dieter Sues. Evolution of Herbivory in Terrestrial Vertebrates: Perspectives from the Fossil Record. Cambridge: Cambridge University Press. pp. 42–78. ISBN 978-0-521-59449-3. 
  24. ^ a b Bonnan M, Senter P. (2007). "Were the basal sauropodomorph dinosaurs Plateosaurus and Massospondylus habitual quadrupeds?"; pp. 139-155 in Barrett, P.M. and Batten, D.J. (eds.), Evolution and Palaeobiology of Early Sauropodomorph Dinosaurs. Special Papers in Palaeontology 77.


External links Edit

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