Yin (1974, p. 25) introduced a new genus, Quadratia for a group of Middle Triassic bivalves in the family Myophoriidae. The type species designated by him is Quadratia quadrata Yin, 1974 [p. 25, pl. 1, figs. 3 (syntype, holotype in original text, right valve), 4a–c (syntype, holotype in original text, left valve), 5 (syntype, paratype in original text); text-fig. 3], the type stratum and locality of which are the Qingyan Formation at Qingyan of Guiyang, Guizhou Province, Southwest China (see also Fang et al., 2009, p. 56, Figs. 16.18–16.21). But this genus name has been preoccupied by Quadratia Muir-Wood and Cooper, 1960 (p. 161, pl. 39, figs. 1–13), which is a member of the Productellidae in the Brachiopoda, with Quadratia hirsutiformis (Walcott, 1884, p. 133, pl. 2, figs. 10, 10a) as the type species, which comes from the White Pine shale of Mississippian age at Applegate Canyon of White Pine County, Nevada, USA. As required by ICZN (International Code of Zoological Nomenclature, Fourth edition; Ride et al., 1999) Article 60.3, I replace Quadratia Yin, 1974, with Guizhoumyophoria, new name, based on the same type species, Quadratia quadrata Yin. The new name is derived from Guizhou Province where the genus occurred.