Silesaurus
| Silesaurus | ||||||||||||
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Live reconstruction of Silesaurus opolensis |
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| Temporal occurrence | ||||||||||||
| Carnium or Norium ( Upper Triassic ) | ||||||||||||
| 230 to 210 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Silesaurus | ||||||||||||
| Dzik , 2003 | ||||||||||||
| Art | ||||||||||||
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Silesaurus is an extinct genus of medium-sized, probably herbivorous, non-avian archosaurs from the immediate family of the dinosaurs . She lived in the Upper Triassic (late Carnian or Norium ) in what is now Poland .
etymology
The only kind and type species of the genus in 2003 by the Polish paleontologists Jerzy Dzik under the name Silesaurus opolensis described . The name "Silesaurus" is derived from "Silesia", the Latin name of Silesia , the region where the type material was found , and "Saurus", the Latinized form of the Greek word σαῦρος, which means " lizard ". The epithet "opolensis" refers to the proximity of the site to the Upper Silesian city of Opole (Opole).
Locations and fossil specimens
 
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The only known place where Silesaurus was found is the clay pit of Krasiejów near Opole in Upper Silesia , Poland. The reddish, clayey find layers were dated to the Upper Triassic, to the late Carnian (approx. 230 million years before today). Alternatively, a Noric age (approx. 220 to 210 million years ago) has been discussed.
The first description of Silesaurus opolensis was based on four largely complete skeletons that have survived approximately in an anatomical context (specimen numbers: ZPAL * Ab III / 361, ZPAL Ab III / 362, ZPAL Ab III / 363 and ZPAL Ab III / 364). In addition, numerous individual bones were found outside of an anatomical context. The number of Silesaurus individuals represented by all of these finds is given as 20 (maximum).
features
In the first description, the following features are listed as diagnostic for Silesaurus and as differentiating from otherwise very similar, relatively closely related, approximately contemporary taxa such as lager peton and Pseudolagosuchus : Number of teeth relatively low, both in the upper jaw (15-16 per jaw half, of which 4 on the premaxillary) and in the lower jaw (11–12 per half of the jaw); the tooth-bearing bones of the lower jaw (Dentalia) have hook-like, upwardly curved, toothless front ends, which in the living animal were probably in a horny sheath; Spine with 25 presacral vertebrae, of which 9–11 cervical vertebrae; elongated, graceful forelimbs; I. Toe ray of hind limbs reduced, with rudimentary metatarsals, but probably without toe limbs. The original description of the sacrum, which consists of four vertebrae, has been corrected below: instead of only two actual sacral vertebrae, which have high, distally fused sacral ribs, the sacrum of Silesaurus consists of three sacral vertebrae and only one rear dorsal vertebra ("dorsosacral vertebra"), which has no sacral ribs.
Silesaurus was a medium-sized archosaur with a reconstructed body length of around 2 meters in total, the long tail of which made up about one meter. The reconstructed skull length is given as only 17 centimeters. The head sat on a relatively long articulated neck. The teeth have a distinctive shape with a relatively slender base on which sits a wide, low, pointed-conical crown. The crown is slightly flattened laterally (medio-lateral) and has a ridge at the front (mesial) and back (distal) that can be covered with small denticles. In addition, when viewed from above, it is often characterized by an irregular, narrow, radial furrow pattern. The body was slim and lightly built, the front limbs were less developed and slightly shorter than the hind limbs. In the tarsus, the two knee (proximal) bones astragalus and calcaneus are firmly connected to one another via a bone suture (suture) so that the hinge line of the ankle runs between the knee and toe (distal) tarsal bones (mesotarsal joint). In addition, the proximal side of the astragalus had a pyramidal hump between the two contact surfaces for the distal ends of the two lower leg bones (tibia and fibula). The pelvis was distinctly three-pronged, with a long rod-shaped pubic bone (pubis) and ischium, and the "back wall" of the acetabulum was closed - the typical pelvis of a Triassic archosaur of the pre-dinosaur era.
Way of life
The light and relatively graceful physique suggests the Silesaurus as a nimble runner. The dinosaur-like structure of his foot (mesotarsal joint, proximal cusp on the astragalus) identifies him as a toe walker and gives reason to suspect that he also moved like a dinosaur - only on his hind legs ( biped ). Other authors assume that he walked on all four legs ( quadruped ). While its habitus suggests more of an agile hunter, its teeth resemble those of bird's-eye dinosaurs (ornithic) and suggest that the Silesaurus was likely a herbivore (herbivore).
Systematics
Even before the four skeletons were discovered in 2001, it was known, based on the discovery of individual bones that could not be identified at the species level, that an archosaur from the bird line ( ornithodira ) occurs in the fossil fauna of the clay pit of Krasiejów , which is or is even related to the dinosaurs is a real dinosaur. In the first description, Silesaurus was classified as standing outside the dinosaurs due to the closed acetabulum and the sacrum with only two real sacral vertebrae. The new discovery in relation to the construction of the sacrum, together with the shape of the teeth and the possession of a "beak" in the lower jaw (albeit without predentals ; see characteristics ), led the investigators to the conclusion that Silesaurus was probably an early representative of the bird basin dinosaur ( Ornithischia) is. However, neither of the two assignments was made on the basis of cladistic analysis. Several such analyzes, some of which were based on very comprehensive data sets, put Silesaurus outside the Dinosauria.
Similar dinosaurs Ornithodiren as Silesaurus who are themselves not yet on the level of development of the dinosaurs, together with the latter a clade that Dinosauriformes is called. In addition, Silesaurus is the type genus of the Silesauridae , a geographically widespread clade of omnivorous or herbivorous Dinosauriformes, which appears as a sister group of the Dinosauria in several cladistic analyzes published since the late 2000s .
swell
- ↑ a b c d e f g h i Jerzy Dzik: A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland. Journal of Vertebrate Paleontology. Vol. 23, No. 3, 2003, pp. 556-574, doi: 10.1671 / A1097 (alternative full text access : ING PAN ).
- ↑ a b c d e f Jerzy Dzik, Tomasz Sulej: A review of the early Late Triassic Krasiejów biota from Silesia, Poland. Palaeontologia Polonica. Vol. 64, 2007, pp. 3-27 ( online ).
- ↑ See Michael Balter: Earliest dinosaurs may have sported feathers. ScienceNews, July 24, 2014, accessed January 5, 2017
- ^ Hans-Dieter Sues, Nicholas C. Fraser: Triassic Life on Land: The Great Transition. Columbia University Press, New York 2010, ISBN 978-0-231-13522-1 , p. 98.
- ↑ a b c Christian F. Kammerer, Sterling J. Nesbitt, and Neil H. Shubin: The first silesaurid dinosauriform from the Late Triassic of Morocco. Acta Palaeontologica Polonica. Vol. 57, No. 2, 2012, pp. 277–284, doi: 10.4202 / app.2011.0015 .
- ^ Max C. Langer, Sterling J. Nesbitt, Jonathas S. Bittencourt, Randall B. Irmis: Non-dinosaurian Dinosauromorpha. Pp. 157-186 in: Sterling J. Nesbitt, Julia B. Desojo, Randall B. Irmis (Eds.): Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin. Geological Society, London, Special Publications. Vol. 379, 2013, doi: 10.1144 / SP379.9 (alternative full text access : ResearchGate ).
- ^ A b Sterling J. Nesbitt: The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History. No. 352, 2011 ( online ), p. 49 and a.
- ↑ Jerzy Dzik, Tomasz Sulej, Andrzej Kaim, Robert Niedźwiedzki: Późnotriasowe cmentarzysko kręgowców lądowych w Krasiejowie na Śląsku Opolskim. Przeglądzie Geologicznym. Vol. 48, No. 3, 2000, pp. 226-235 ( HTML version on the website of the Institute of Paleontology of the Polish Academy of Sciences).
- ↑ Martín D. Ezcurra: A review of the systematic position of the dinosauriform archosaur Eucoelophysis baldwini Sullivan & Lucas, 1999 from the upper Triassic of New Mexico, USA. Geodiversitas. Vol. 28, No. 4, 2006, pp. 649-684 ( online )
- ^ Max C. Langer, Michael J. Benton: Early Dinosaurs: a phylogenetic study. Journal of Systematic Palaeontology. Vol. 4, No. 4, 2006, pp. 309–358, doi: 10.1017 / S1477201906001970 (alternative full text access : ResearchGate )
- ↑ Randall B. Irmis, Sterling J. Nesbitt, Kevin Padian, Nathan D. Smith, Alan H. Turner, Daniel Woody, Alex Downs: A Late Triassic Dinosauromorph Assemblage from New Mexico and the Rise of Dinosaurs. Science. Vol. 317, No. 5836, 2012, pp. 358–361, doi: 10.1126 / science.1143325 (alternative full text access: ResearchGate ).
- ^ A b Max C. Langer, Martin D. Ezcurra, Jonathas S. Bittencourt, Fernando E. Novas: The origin and early evolution of dinosaurs. Biological Reviews. Vol. 85, No. 1, 2010, pp. 55–110, doi: 10.1111 / j.1469-185X.2009.00094.x (alternative full-text access : Universidade de São Paulo ).
- ^ A b Sterling J. Nesbitt, Christian A. Sidor, Randall B. Irmis, Kenneth D. Angielczyk, Roger MH Smith, Linda A. Tsuji: Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature. Vol. 464, 2010, pp. 95-98, doi: 10.1038 / nature08718 .
- ^ A b Sterling J. Nesbitt: The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History. No. 352, 2011 ( online ), pp. 209, 239 ff. And a.
Web links
- Silesaurus. Datasheet in the Paleobiology Database