Silesauridae
| Silesauridae | ||||||||||||
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Fossil remains of the genus Diodorus from the Argana basin of Morocco: Incomplete dentals (A, holotype of Diodorus scytobrachion ), as well as a single isolated tooth (B; not to scale), but an example for silesaurids |
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| Temporal occurrence | ||||||||||||
| Central and Upper Triassic | ||||||||||||
| 247.2 to 208.5 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Silesauridae | ||||||||||||
| Langer et al., 2009 | ||||||||||||
The Silesauridae are a relatively diverse monophyletic group ( clade ) of medium-sized herbivorous or omnivorous bird-line archosaurs ( Ornithodira ) from the immediate family of the dinosaurs . They lived from the early Central Triassic ( Anisian ) to the younger Upper Triassic ( Norium ) in the western part of the supercontinent Pangea .
Taxonomic history and definition
The name "Silesauridae" was coined in 2009 in a review of the state of research on the early dinosaurs and their immediate ancestors. The reason for this was the knowledge, based on cladistic methods, that in the Middle and Early Upper Triassic, that is, in the period that is of particular interest for understanding the evolution of the first dinosaurs, several relatively specialized genera in the lineage of the dinosaurs ( basal dinosauromorpha ) existed, which were more closely related than with the first dinosaurs as well as with more original representatives of the same line of development (see systematics and localities ). The original stem-based definition of the taxon was therefore:
- " All archosaurs that are more closely related to Silesaurus opolensis than to Heterodontosaurus tucki or Marasuchus lilloensis ."
In the following, this definition was modified as follows , taking into account the crown group taxa of the archosaurs:
- " The most inclusive clade that contains Silesaurus opolensis , but not Passer domesticus , Triceratops horridus or Alligator mississippiensis ."
features
The following features are considered to be especially diagnostic for the Silesaurids: Tooth-bearing bone of the lower jaw (dentals) at the front end edentulous and tapering; Tooth crowns in the main bone of the upper jaw (maxillary) and dentals relatively short and almost triangular in side view; Head of the thighbone (femur) clearly separated from the shaft by a recess on the inside (medial); Upper side of the femoral head with notch running transversely to the longitudinal axis of the body (medio-lateral).
All silesaurids were medium-sized, relatively graceful animals with a relatively long neck and rather small head and relatively long limbs.
ecology
Their special dentition shows that silesaurids were probably herbivores (herbivores) or at least omnivores (omnivores). Their relatively graceful physique makes them appear as escape animals . The relatively long forelimbs suggest that they walked on four legs (quadruped), although some representatives were previously reconstructed as two-legged (bipede) runners under the impression of their “dinosaur-like character”. Probable predators were large archosaurs from the ancestral group of crocodiles (basal crurotarsier, " Rauisuchier "), or, among the geologically youngest representatives, early theropods .
Systematics and locations
The Silesauriden are lineages representatives of birds within the Ornithodira , which means they are more closely related to birds and non-avian dinosaurs than flying reptiles (Pterosauria). In cladistic analyzes they form a monophyletic grouping ( clade ), which is the sister group of the dinosaurs . However, some such analyzes resulted in hypotheses in which the silesaurids appear as a paraphyletic “ grade ” in the “higher” part of the dinosaur lineage.
The following simplified cladogram shows the position of the silesaurids within the parent group of birds (according to Nesbitt, 2011), clades marked with an "H" contain herbivorous representatives:
| Archosauria ( Avesuchia ) |
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If this kinship hypothesis is correct, the silesaurids provided evidence that adaptive radiation was already underway in the middle Triassic, not only in the crocodile line, but also in the archosaur bird line, with groups with herbivorous representatives in both lines ( Crurotarsi: aetosaurs ; ornithodira: silesaurids) emerged. In the Upper Triassic, radiation in the bird's line eventually led to the creation of dinosaurs. Their geologically oldest representatives ( Herrerasaurus , Eoraptor ) show that the last common ancestor of the dinosaurs was a carnivore, and that the herbivory in this clade was acquired one more time, in the two main lines (Ornithischia, Saurischia) each independently of one another .
Within the Silesauridae, the following 9 to 10 monotypical genera are currently (2017) differentiated: *
| genus | Lithostratigraphy | geochronology | Geographical region |
|---|---|---|---|
| Asilisaurus Nesbitt et al., 2010 | Manda layers | anise | Tanzania |
| Lutungutali Peecook et al., 2013 | Ntawere formation | anise | Zambia |
| Lewisuchus Romer , 1972 | Chañares formation | Ladin | La Rioja (Argentina) |
| Pseudolagosuchus Arcucci , 1987 ** | Chañares formation | Ladin | La Rioja (Argentina) |
| Silesaurus Dzik , 2003 § | Middle Keuper | Carn | Poland |
| Ignotosaurus Martínez et al., 2013 | Ischigualasto formation | Carn | San Juan (Argentina) |
| Diodorus Kammerer et al., 2012 | Timezgadiouine formation | ? Karn - Nor | Morocco |
| Technosaurus Chatterjee , 1984 | Dockum group | Nor | Texas (USA) |
| Sacisaurus Ferigolo & Langer , 2007 | Caturrita formation | Nor | Rio Grande do Sul (Brazil) |
| Eucoelophysis Sullivan & Lucas , 1999 | Chinle formation | Nor - Rhät | New Mexico (USA) |
For most of these genera, relatively little and incomplete material is known. Silesaurus is so far (as of 2017) the only genus of which largely complete skeletons have been found, and much of the knowledge about silesaurids comes from studying these fossils. The incomplete fossil record makes it difficult to determine the exact relationships within the group. In the cladistic analyzes that were carried out in connection with the three first publications of the three genera described last, only the data from 6 "genera" were included ( Asilisaurus , Lewisuchus / Pseudolagosuchus , Silesaurus , Sacisaurus , Eucoelophysis and the new genus) . Lewisuchus / Pseudolagosuchus were always identified as the most basal and Asilisaurus as the “next higher” taxon. The cladogram below shows the unresolved consensus from the results of the three analyzes (Kammerer et al., 2012; Peecook, 2013; Martínez et al., 2013):
| Silesauridae |
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- ↑ 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 (online 2009), pp. 55–110, doi: 10.1111 / j.1469-185X.2009.00094.x (alternative full-text access : Universidade de São Paulo ).
- ↑ a b c d 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.
- ↑ a b c d e 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 .
- ↑ 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 ).
- ↑ Jorge Ferigolo, Max C. Langer: A Late Triassic dinosauriform from south Brazil and the origin of the ornithischian predentary bone. Historical Biology. Vol. 19, No. 1, 2007, pp. 556-574, doi: 10.1080 / 08912960600845767 (alternative full text access : ResearchGate ).
- ↑ Robert Niedźwiedzki, Stephen L. Brusatte, Tomasz Sulej, Richard J. Butler: Basal dinosauriform and theropod dinosaurs from the mid-late Norian (Late Triassic) of Poland: Implications for Triassic dinosaur evolution and distribution. Paleontology. Vol. 57, No. 6, 2014, pp. 1121–1142, doi: 10.1111 / pala.12107 (alternative full-text access: ResearchGate ).
- ^ A b c 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 .
- ↑ 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 )
- ↑ a b Brandon R. Peecook, Christian A. Sidor, Sterling J. Nesbitt, Roger MH Smith, J. Sebastien Steyer, Kenneth D. Angielczyk: A new silesaurid from the upper Ntawere Formation of Zambia (Middle Triassic) demonstrates the rapid diversification of Silesauridae (Avemetatarsalia, Dinosauriformes). Journal of Vertebrate Paleontology. Vol. 33, No. 5, 2013, pp. 1127–1137, doi: 10.1080 / 02724634.2013.755991 (alternative full text access: ResearchGate ).
- ↑ a b Ricardo N. Martínez, Cecilia Apaldetti, Oscar A. Alcober, Carina E. Colombi, Paul C. Sereno, Eliana Fernandez, Paula Santi Malnis, Gustavo A. Correa, Diego Abelin: Vertebrate succession in the Ischigualasto Formation. Journal of Vertebrate Paleontology. Vol. 32, No. 6 [Suppl .: SVP Memoir 12 - Basal sauropodomorphs and the vertebrate fossil record of the Ischigualasto Formation (Late Triassic: Carnian-Norian) of Argentina ], 2013, pp. 10-30, doi: 10.1080 / 02724634.2013.818546 (alternative full text access: ResearchGate ).
- ↑ Silesauridae. Paleobiology Database, data sheet with further links
- ↑ 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 , online supplement ( PDF 750 kB).
