Silesaurus opolensis (圖片來源：Szymon Górnicki，採用  CC BY-SA 4.0  授權) In traditional dinosaur classification, researchers divide dinosaurs into two major branches according to pelvic structure: Ornithischia  and Saurischia  (the latter further divided into Theropoda and Sauropodomorpha). This framework was first proposed by Harry Seeley in 1888. However, alternative views on dinosaur classification have also been suggested. One hypothesis grouped sauropodomorphs and ornithischian