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.

 
Systematic position after Nesbitt (2011):
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.
 
Systematic position after Nesbitt (2011):
Silesaurus