Heishanosaurus

The type specimens are represented by the blocks IVPP V25322, 25323 and 25324, were discovered in September 2003 at the Badaohao locality, in Heishan County, Liaoning Province, China, in sediments belonging to the Shahai Formation. The Shahai Formation is generally thought to overlie the Jiufotang Formation and has an uncertain Aptian-Albian age, based on the radiometic dating of the Jiufotang Formation. The remains are disarticulated inside the blocks, and were scanned using microcomputed tomography.[1]

Remains include disarticulated skull bones, along with limited postcranial remains. Based on the size of the skull, the animal likely around 16 cm long, similar in size to Cteniogenys. The skull retains an open lower temporal fenestra, as in Cteniogenys, Coeruleodraco and neochoristoderes, but which is closed in the majority of Early Cretaceous Asian "non-neochoristoderans".[1]

In a strict concensus phylogenetic analysis, it was recovered as a basal choristodere, more derived than Cteniogenys, but more primitive than neochoristoderes or the weakly supported clade containing all other Asian Early Cretaceous "non-neochoristoderans" with closed temporal fenestrae, which was informally named the "allochoristoderes" in the study. Heishanosaurus was recovered in a polytomy with the Late Jurassic Coeruleodraco, despite its much younger age.[1]