Fig. 2. Sedimentary profile of the Suhongtu quarry. A. Laminated to very thinly bedded, red and blue−gray unit with a total thickness of 1.3 m. More massive mudstones (not shown) under− and overlie this unit. Main boneproducing horizon located near base (marked by> <) at top of mottled interval. Scale bar 10 cm. B. Close−up sedimentary profile of the Suhongtu quarry. The principal bone horizon lies at the midway point of the hammer handle. This unit consists of abundant convoluted bedding and is marked by blue−gray mottling near its top. A thin, light−colored sandstone immediately overlies this unit. Hammer length equals 27.6 cm. C. Close−up of main bone−bearing unit with partially collapsed, infilled footprint structures in laminated claystone. Ripple−scale cross−stratification (R) in thin (1 to 2 cm) very fine sandstone that lies immediately above the main bone horizon. A great abundance of mottling occurs near the top of this bone−bearing unit. Asterisks mark the lower ends of V−shaped disruption structures, where footfalls and digits have bisected underlying laminated units. The down curved lamina and uniform fills of these structures suggest the original substrate was soft and only partially consolidated. Scale bar 10 cm.