Bashanosaurus (meaning "Bashan lizard") is an extinct genus of stegosaurian dinosaur from the Middle Jurassic Shaximiao Formation of Yunyang County, China.

In 2016, a quarry of dinosaur fossils belonging to the lower Shaximiao Formation was found in Laojun Village of Pu’an Township in Yunyang County, Chongqing Municipality, China.

[1] The holotype specimen, CLGPR V00006-1, includes one dorsal and two caudal vertebrae, the right scapulocoracoid, a partial left hindlimb (femur, tibia, fibula, and a metatarsal), several fragmentary ribs, and three dermal armor pieces (two plates and one spine).

A second specimen was referred, CLGPR V00006-2, consisting of five dorsal vertebrae, the right tibia and fibula, partial ribs, and an incomplete dermal plate.

[1] In 2022, Dai et al. described Bashanosaurus primitivus as a new genus and species of basal stegosaurian based on these fossil remains.

It includes a partial cranium (the frontals, parietals, and a braincase), a dorsal vertebra, and a small broken dermal spine.

Isaberrysaura, an Argentinian stegosaur originally described in 2017 as a basal ornithopod within the Neornithischia, may date to the earlier Bajocian age.

[4][5] The Bathonian–Callovian-aged El Mers II Formation of Morocco has also yielded the remains of the early stegosaurs Adratiklit and Thyreosaurus, described in 2020 and 2024, respectively.

[8] As a stegosaur, Bashanosaurus would have been a quadrupedal herbivore with a paired row of a combination of large plates and spines running along the top of the animal from the neck to the tail tip.

[1] A small portion of the skeleton of Bashanosaurus is known from three different specimens, including vertebrae from the back and tail, ribs, bones from the shoulder and hind limbs, and osteoderms.

[1] The Bashanosaurus holotype includes a well-preserved right scapulocoracoid, missing part of the distal end of the scapula and the dorsal edge of the coracoid.

[1] The fossil material of Bashanosaurus demonstrates a unique blend of features typically seen in both adult and immature animals.

[11] In the phylogenetic analyses in their 2022 description of Bashanosaurus, Dai et al. recovered it in the basalmost clade within the Stegosauria, as the sister taxon to the Late Jurassic Chungkingosaurus.

[13] Using analyses of sedimentology and elemental geochemistry, the Shaximao Formation has been interpreted as representing a semi-arid to semi-humid region with meandering rivers and an intricate seasonal lake system.

The dinosaurs discovered include sauropods (Abrosaurus, Bashunosaurus, Dashanpusaurus, Datousaurus, Omeisaurus spp., and Protognathosaurus),[17] theropods (Chuandongocoelurus, Gasosaurus, Kaijiangosaurus, Szechuanosaurus, Xuanhanosaurus, and an indeterminate megalosaurid), neornithischians (Agilisaurus, Hexinlusaurus, and Xiaosaurus),[18] and the stegosaurian Huayangosaurus.

[2] The non-dinosaurian fauna includes pterosaurs (Angustinaripterus), turtles (Chengyuchelys spp., Plesiochelys, and Trionyx), crocodyliforms (Teleosaurus, Sunosuchus, and Hsisosuchus), pliosaurid plesiosaurs, therapsids (Bienotheroides and Polistodon), fish (Hybodus, Yuchoulepis, Lepidotes, and Ceratodus), and amphibians (Sinobrachyops).

[19] The upper layers of the formation, which date to younger ages, have also yielded a similar dinosaur fauna, including several stegosaurs (Chialingosaurus, Chungkingosaurus, Gigantspinosaurus, Tuojiangosaurus, and Yingshanosaurus) and various sauropods, theropods, basal ornithischians.