[1] Uppsala Univ, Dept Earth Sci, Palaeobiol, Villav 16, SE-75236 Uppsala, Sweden
[2] Macquarie Univ, Dept Biol Sci, Sydney, NSW 2109, Australia
[3] Swedish Museum Nat Hist, Dept Palaeobiol, Box 50007, SE-10405 Stockholm, Sweden
[4] Northwest Univ, Early Life Inst, Xian 710069, Peoples R China
[5] Northwest Univ, Dept Geol, State Key Lab Continental Dynam, Xian 710069, Peoples R China
[6] Univ New England, Palaeosci Res Ctr, Sch Environm & Rural Sci, Armidale, NSW 2351, Australia