Silesaurus

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Silesaurus
Temporal range: Late Triassic, Carnian
Silesaurus1.jpg
Restoration
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauromorpha
Clade: Dinosauriformes
Clade: Silesauridae
Genus: Silesaurus
Dzik, 2003
Species
  • S. opolensis Dzik, 2003 (type)

Silesaurus is a genus of dinosauriforms from the Late Triassic, approximately 230 million years ago in the Carnian faunal stage of what is now Poland.

Fossilized remains of Silesaurus have been found in the Keuper Claystone in Krasiejów near Opole, Silesia, Poland, which is also the origin of its name.[1] The type species, Silesaurus opolensis, was described by Jerzy Dzik in 2003. It is known from some 20 skeletons, making it one of the best-represented of the early dinosaurs and related animals.

Characteristics[edit]

Silesaurus opolensis and Polonosuchus silesiacus models in Poland

Silesaurus measured approximately 2.3 meters long (7.5 ft), and was facultatively bipedal. It was light and built for speed.

Silesaurus was an herbivore. The teeth were small, conical, and serrated. The tip of the dentary has no teeth, and some paleontologists think that it may have been covered by a beak.

Phylogeny[edit]

Size compared to a human
Restored skeleton

Most scientists think that Silesaurus was not a dinosaur, but rather a dinosauriform. Dinosaurian features lacking in Silesaurus include an enlarged deltopectoral crest (a muscle attachment on the humerus), and epipophyses (enlarged tendon attachment above the postzygapophysis) on the cervical vertebrae.

However, Silesaurus has some dinosaurian characteristics as well:

  • a brevis shelf (a bone surface on the ilium that functions as an attachment site for tail muscles)
  • ischium with a slender shaft
  • femur with a reduced tuberosity that borders the ligament of the femoral head
  • a prominent lesser trochanter
  • an overlap of the ascending process of the astragalus with the tibia
  • a concave proximal articular surface for the reception of the distal end of the fibula on the calcaneum

As a result, alternative theories place Silesaurus at or near the base of the ornithischian dinosaurs. Other scientists propose a basal link between the prosauropods and ornithischians.[1]

Systematic position after Nesbitt (2011):[2]

Ornithodira 
 Pterosauromorpha 

Scleromochlus



Pterosauria



 Dinosauromorpha 
 Lagerpetonidae 

Lagerpeton



Dromomeron



 Dinosauriformes 

Marasuchus



 Silesauridae 

Lewisuchus/Pseudolagosuchus




Asilisaurus




Eucoelophysis




Sacisaurus



Silesaurus






 Dinosauria 
 Saurischia 

Theropoda



Sauropodomorpha




Ornithischia







References[edit]

  1. ^ a b Dzik, J. (2003). "A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland." Journal of Vertebrate Paleontology, 23(3): 556-574.
  2. ^ Nesbitt, 2011. The early evolution of archosaurs: Relationships and the origin of major clades. Bulletin of the American Museum of Natural History. 352, 292 pp.

External links[edit]