1. Palaeoecosystems Group; Department of Earth Sciences; Durham University; Durham DH1 3LE UK
2. Early Life Institute and Department of Geology; State Key Laboratory for Continental Dynamics; Northwest University; Xi'an 710069 China
3. Instituto de Geociencias CSIC; UCM and Departamento de Paleontología; Facultad de Ciencias Geológicas; José Antonio Novais 12 28040 Madrid Spain