Yingshanosaurus (meaning "Yingshan lizard") is an extinct genus of stegosaurian dinosaurs from the Middle Jurassic of what is now Southwestern China.

After its discovery and scientific description, the validity of Yingshanosaurus was questioned by some paleontologists who were unaware of the research published on the species in China.

This formation has also yielded abundant fossils of diverse dinosaurs including many sauropods, theropods, early ornithischians, and stegosaurs, in addition to turtles, crocodyliforms, mammal relatives, and fish.

While all of the stegosaurs contemporary with Yingshanosaurus were among the more "primitive" species in this clade, its anatomy suggests it had derived traits consistent with members of the more exclusive subfamily Stegosaurinae.

In 1983, a villager in the town of Jichuan discovered a partial associated dinosaur skeleton while digging the foundation for his house in Yingshan County of Sichuan Province, China.

[6] A mounted skeleton of the holotype specimen was displayed in a Japanese exhibition of Chinese dinosaurs through 1992 and 1993, where it was also referenced under the mistranslated title "Yunshanosaurus".

[8] In 1994, Zhu Songlin described Yingshanosaurus jichuanensis as a distinct genus and species of stegosaurian dinosaurs, establishing the partial skeleton as the holotype specimen, CV00722.

The generic name, Yingshanosaurus, combines a reference to the discovery of the specimen in Yingshan County with the Greek σαῦρος (sauros), meaning "reptile".

[3] Due to the limited availability of Zhu's 1994 publication, the validity of Yingshanosaurus went unnoticed by many researchers outside of China; in their 2006 review of Chinese stegosaurs, Maidment & Wei stated they were unable to find a description, a diagnosis, or any published figures of the Yingshanosaurus fossils, and, as such, the name should be recognized as a nomen nudum.

[14][15][4] As a stegosaur, Yingshanosaurus would have been a quadrupedal herbivore with a row of large paired plates and spines along the top of the animal from the neck to the tail tip.

[8][13] This is similar to the more well-known stegosaur genus Kentrosaurus from the Tendaguru Formation of Tanzania, which is estimated at 4 metres (13 ft) long.

[18] Based on the fusion of several bones, including the scapula to the coracoid and the tibia to the fibula, the Yingshanosaurus holotype can be identified as a mature adult individual.

The length and width of the centrum are approximately equal, and the articular surfaces are slightly concave but nearly amphiplatian (flat).

Two associated middle dorsal vertebrae are preserved, although both are missing the neural spines, transverse processes, and parts of the centra.

Two middle caudal vertebrae are also preserved, demonstrating laterally compressed biconcave centra that are longer than they are wide.

The plates of Yingshanosaurus are proportionally small, similar in relative scale to those of Kentrosaurus and Dacentrurus, but not the much larger ones of Stegosaurus.

These other stegosaurs, which include Huayangosaurus and its relatives, have similar forelimb and hindlimb lengths, spikelike plates, and more prominent sacral fenestrae.

Zhu argued that the comparatively short forelimbs, broad plates, reinforced pelvic girdle with a nearly fused sacral region, tall dorsal vertebral neural spines, and expanded caudal neural spine tips were evidence of this classification.

[3] The presence of a derived stegosaurine like Yingshanosaurus in a formation otherwise dominated by more "primitive" taxa led Hao et al. (2018) to construct a tentative cladogram to illustrate the evolutionary relationships of Chinese stegosaurs.

While they did not reconstruct the precise relationships of stegosaurids, they speculated that the taxa diverged in the order displayed in the diagram below, although they noted that the placements of Chialingosaurus and Jiangjunosaurus are tentative.

Analyses of the sedimentology and elemental geochemistry of this formation indicate that it represents a semi-arid to semi-humid depositional environment with meandering rivers and a complex seasonal lake system.

[21] These rock layers of the Upper Shaximiao Formation have not been precisely dated, but estimates in 2011 proposed a Bajocian–Bathonian age range in the Middle Jurassic epoch.

[2] Many other fossil taxa have been found in localities of the Upper Shaximiao Formation, but they may not have been strictly coeval with Yingshanosaurus.

[1] The lower layers of the formation, which date to older ages, have also yielded a similar dinosaur fauna, including the stegosaurs Bashanosaurus and Huayangosaurus and various sauropods, theropods, basal ornithischians.