Silesaurus

Silesaurus Temporal range: Late Triassic, 230 Ma PreЄ Є O S D C P T J K Pg N ↓
Reconstructed skeleton
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauriformes
Clade:	Dracohors
Clade:	†Silesauridae
Genus:	†Silesaurus Dzik, 2003
Species
S. opolensis Dzik, 2003 (type)

Silesaurus is a genus of silesaurid dinosauriform 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 dinosauriformes.

Description

Size compared to a human

Silesaurus measured approximately 2.3 meters (7.5 feet) long, 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.

Classification

S. opolensis restored without feather-like filaments

Silesaurus opolensis and Polonosuchus silesiacus models in Poland

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 hypotheses place Silesaurus at or near the base of the ornithischian dinosaurs. Other scientists propose a basal link between the basal sauropodomorphs and ornithischians.^[1]

Systematic position after Nesbitt (2011):^[2]

References