The earliest ceratopsian from the Tuchengzi Formation of Liaoning, China

A new ceratopsian specimen, Chaoyangsaurus youngi gen. et sp. nov., was col lected from the Tuchengzi Formation (Middle or Late Jurassic) of Liaoning, China. Distinctive characteristics of the new species include quadratojugal overlapping posterior side of quadrate shaft; lack of a broad lateral surf ace of the quadrate shaft; convex posterior margin of the ventral portion o f the quadrate; a ridge between the planar lateral and Ventral surface of t he angular. The discovery of Chaoyangsaurus youngi extends the record of ce ratopsian from back in time from the Early Cretaceous into the Middle or La te Jurassic. Some characters of C. youngi may suggest a close relationship between Ceratopsia and Heterodontosauridae.